Fine Structure Pattern Research Articles

The Influence of Reservoir Architecture on the Connectivity of the Shahejie Formation in the Liuzhong Oilfield

The lack of research on fine reservoir structure and sand body patterns in the Jidong Oilfield currently restricts the efficient development of the oilfield. Therefore, this article mainly focuses on the study of the main types of facies of the Shahejie Formation, sand body splicing patterns, and the degree of sand-body connectivity. The interpretation and analysis of well-logging, three-dimensional (3D) seismic, and production data were used to lay the foundation for the study and evaluate the remaining oil distribution. The results indicate that the reservoir sandstones in the study area were mainly deposited in a submerged distributary channel, mouth bar, and distributary channel flank. Using logging information to identify individual sands, a deltaic sand assemblage pattern is proposed by analyzing the sedimentary architecture. In the vertical direction, the deltaic sand body collocation style can be divided into cut-and-stack and separated types. In the lateral direction, the multi-stage sand bodies exhibit three collocation patterns: the side-cutting type, the mouth bar contact type, and the submerged distributary channel flank contact type. The degree of sand-body connectivity under different splicing patterns was analyzed and verified using production dynamic data. It was found that the sand body splicing pattern with a vertical up-cut stack and the sand body splicing pattern with a lateral up-cut had the best inter-sand-body connectivity.

Fine structure and assembly pattern of a minimal myophage Pam3

The myophage possesses a contractile tail that penetrates its host cell envelope. Except for investigations on the bacteriophage T4 with a rather complicated structure, the assembly pattern and tail contraction mechanism of myophage remain largely unknown. Here, we present the fine structure of a freshwater Myoviridae cyanophage Pam3, which has an icosahedral capsid of ~680 Å in diameter, connected via a three-section neck to an 840-Å-long contractile tail, ending with a three-module baseplate composed of only six protein components. This simplified baseplate consists of a central hub-spike surrounded by six wedge heterotriplexes, to which twelve tail fibers are covalently attached via disulfide bonds in alternating upward and downward configurations. Invitro reduction assays revealed a putative redox-dependent mechanism of baseplate assembly and tail sheath contraction. These findings establish a minimal myophage that might become a user-friendly chassis phage in synthetic biology.

ALMA as a Prominence Thermometer: First Observations

Abstract We present first prominence observations obtained with Atacama Large Millimeter Array (ALMA) in Band 3 at the wavelength of 3 mm. High-resolution observations have been coaligned with the MSDP Hα data from Wrocław–Białków large coronagraph at similar spatial resolution. We analyze one particular cotemporal snapshot, first calibrating both ALMA and MSDP data and then demonstrating a reasonable correlation between both. In particular, we can see quite similar fine-structure patterns in both ALMA brightness-temperature maps and MSDP maps of Hα intensities. Using ALMA, we intend to derive the prominence kinetic temperatures. However, having current observations only in one band, we use an independent diagnostic constraint, which is the Hα line integrated intensity. We develop an inversion code and show that it can provide realistic temperatures for brighter parts of the prominence where one gets a unique solution, while within faint structures, such inversion is ill conditioned. In brighter parts, ALMA serves as a prominence thermometer, provided that the optical thickness in Band 3 is large enough. In order to find a relation between brightness and kinetic temperatures for a given observed Hα intensity, we constructed an extended grid of non-LTE prominence models covering a broad range of prominence parameters. We also show the effect of the plane-of-sky filling factor on our results.

Laser-assisted decay spectroscopy and mass spectrometry of Au178

A comprehensive study of the isotope 178 Au has been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in 178 Au were identified—a low-spin ground state and a high-spin isomer—each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in 178 Au was determined to be E ∗ = 189 ( 14 ) keV . The α -decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus 174 Ir . Nuclear spin assignments of I ( 178 Au g ) = ( 2 , 3 ) and I ( 178 Au m ) = ( 7 , 8 ) are made based on the observed β -decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for 178 Au g , m .

Fine structures in Raman spectra of tetrahedral tetrachloride molecules in femtosecond coherent spectroscopy.

Herewith, we present fast Fourier transforms of time resolved signals, obtained by use of the femtosecond transient transmission (TT) spectroscopy, for three tetrachlorides, CCl4, SiCl4, and GeCl4, and chloroform, CHCl3. Due to coherent excitation of molecules, the isotopic splitting of their spectral bands in the range of symmetric stretching vibration can be observed with high resolution not available in spontaneous Raman scattering. The intensity distribution in the isotopic fine structure pattern appears to differ for various studied molecules, which is explained by the role of intermolecular interactions and the local order of molecules in the liquids. In particular, in SiCl4, the vibrational band exhibits anomalous ratios of the peak amplitudes, which do not agree with the natural abundance of the isotopologues. Using the simple oscillatory model of the liquid and fitting theoretical curves to the experimental results, we have been able to find the intermolecular force constants for all three liquids and to formulate the conclusion that the anomalous spectral pattern in SiCl4 results from strong interactions between the closest Cl atoms belonging to adjacent molecules. Application of the windowed Fourier transform enables us to study the dynamics of intermolecular interactions. The strength of intermolecular interactions in CCl4, SiCl4, and GeCl4, found by the TT technique, is compared with the results obtained by means of the femtosecond optical Kerr effect spectroscopy.

Cochlear Mechanisms and Otoacoustic Emission Test Performance.

This study aims to determine the impact of controlling cochlear-source mechanism on the accuracy with which auditory status is identified using otoacoustic emissions (OAEs) in two groups of subjects with normal hearing (NH) and subjects with mild to moderate hearing loss. Data were collected from 212 subjects with NH and with mild to moderate hearing loss who fell into two categories based on a distortion product OAE (DPOAE) screening protocol: the uncertain-identification group (where errors were likely) and the certain-identification group (where errors were unlikely). DPOAE fine-structure patterns were recorded at intervals surrounding f2 = 1, 2 and 4 kHz (f2/f1 ratio = 1.22), with L2 = 35, 45, and 55 dB SPL (L1/L2 ratio = 10 dB). The discrete cosine transform was used to smooth fine structure, limiting the source contribution to the distortion source only. Reflection-source OAEs were also recorded using amplitude-modulated stimulus frequency OAEs (AM-SFOAE). Area under the relative operating characteristic (AROC) curve was used to quantify test accuracy when the source contribution was controlled versus the condition where both sources contribute. Additionally, failure rate, fixed at 5% for NH ears, as a function of behavioral-threshold category was evaluated. When data for the entire subject group were examined, reducing the reflection-source contribution to the DPOAE did not result in better test performance than the best control condition at any frequency tested. When the subjects with NH were restricted to those with confirmed fine structure, AROC analyses indicated that reducing the reflection-source contribution resulted in several small increases in the accuracy (2%-5%) with which auditory status was identified relative to the best control condition. This improvement was observed for the lowest stimulus levels (i.e., L2 = 35 or 45 dB SPL). In this subset of subjects, distortion-source DPOAEs resulted in more accurate identification of mild hearing loss for a fixed false-positive rate of 5% in NH ears at lower L2's, conditions with poor accuracy in the larger group of subjects. The impact of controlling the source contribution on the identification of moderate losses was less clear in the reduced subject group, with some conditions where the distortion-source DPOAE was more accurate than the control condition and other conditions where there was no change. There was no evidence that reflection-source AM-SFOAEs more accurately identified ears with hearing loss when compared to any of the DPOAE conditions in either the large or reduced group of subjects. While improvements in test accuracy were observed for some subjects and some conditions (e.g., mild hearing losses and low stimulus levels in the reduced subset of subjects), these results suggest that restricting cochlear source contribution by "smoothing" DPOAE fine structure is not expected to improve DPOAE test accuracy in a general population of subjects. Likewise, recording reflection-source OAEs using the AM-SFOAE technique would not be expected to more accurately identify hearing status compared to mixed- or single-source DPOAEs.

Frequency-dependent fine structure in the frequency-following response: The byproduct of multiple generators

The frequency-following response (FFR) is an auditory-evoked response recorded at the scalp that captures the spectrotemporal properties of tonal stimuli. Previous investigations report that the amplitude of the FFR fluctuates as a function of stimulus frequency, a phenomenon thought to reflect multiple neural generators phase-locking to the stimulus with different response latencies. When phase-locked responses are offset by different latencies, constructive and destructive phase interferences emerge in the volume-conducted signals, culminating in an attenuation or amplification of the scalp-recorded response in a frequency-specific manner. Borrowing from the literature on the audiogram and otoacoustic emissions (OAEs), we refer to this frequency-specific waxing and waning of the FFR amplitude as fine structure. While prior work on the human FFR was limited by small sets of stimulus frequencies, here, we provide the first systematic investigation of FFR fine structure using a broad stimulus set (90 + frequencies) that spanned the limits of human pitch perception. Consistent with predictions, the magnitude of the FFR response varied systematically as a function of stimulus frequency between 16.35 and 880 Hz. In our dataset, FFR high points (local maxima) emerged at ∼44, 87, 208, and 415 Hz with FFR valleys (local minima) emerging ∼62, 110, 311, and 448 Hz. To investigate whether these amplitude fluctuations are the result of multiple neural generators with distinct latencies, we created a theoretical model of the FFR that included six putative generators. Based on the extant literature on the sources of the FFR, our model adopted latencies characteristic of the cochlear microphonic (0 ms), cochlear nucleus (∼1.25 ms), superior olive (∼3.7 ms), and inferior colliculus (∼5 ms). In addition, we included two longer latency putative generators (∼13 ms, and ∼25 ms) reflective of the characteristic latencies of primary and non-primary auditory cortical structures. Our model revealed that the FFR fine structure observed between 16.35 and 880 Hz can be explained by the phase-interaction patterns created by six generators with relative latencies spaced between 0 and 25 ms. In addition, our model provides confirmatory evidence that both subcortical and cortical structures are activated by low-frequency (<100 Hz) tones, with the cortex being less sensitive to frequencies > 100 Hz. Collectively, these findings highlight (1) that the FFR is a composite response; (2) that the FFR at any given frequency can reflect activity from multiple generators; (3) that the fine-structure pattern between 16.35 and 880 Hz is the collective outcome of short- and long-latency generators; (4) that FFR fine structure is epiphenomenal in that it reflects how volume-conducted electrical potentials originating from different sources with different latencies interact at scalp locations, not how these different sources actually interact in the brain; and (5) that as a byproduct of these phase-interaction patterns low-amplitude responses will emerge at some frequencies, even when the underlying generators are fully functioning. We believe these findings call for a re-examination of how FFR amplitude is interpreted in both clinical and experimental contexts.

Electron Paramagnetic Resonance Study of Guest Molecule-Influenced Magnetism in Kagome Metal–Organic Framework

We present a continuous-wave electron paramagnetic resonance (EPR) study of Cu(ipa)(H2O) (ipa stands for isophthalate ligand) metal–organic framework (MOF) that is based on the kagome topology. The main structural unit of this compound is a copper paddle-wheel (PW) consisting of two Cu2+ ions interconnected via four carboxylate groups in the syn–syn fashion. X- and Q-band EPR measurements of this MOF allow us to probe distinct magnetic interactions of different magnitudes that originate from these dinuclear units. EPR experiments performed at different temperatures reveal that two Cu2+ ions in a single PW are antiferromagnetically coupled to the total spin S = 0 state with the exchange coupling constant J = −285 cm–1. The fine structure pattern observed in the spectra indicates the thermal population of the excited triplet S = 1 spin states of the Cu2+ pairs. Spectral simulations are used to determine the fine and hyperfine structure tensors of the PW units. At higher temperatures a collapse of the fine s...

The excited spin-triplet state of a charged exciton in quantum dots

We report on spectroscopic studies of resonances related to ladder of states of a charged exciton in single GaAlAs/AlAs quantum dot structures. Polarization-resolved photoluminescence, photoluminescence excitation and photon-correlation measurements were performed at low (T = 4.2 K) temperature also in magnetic field applied in Faraday configuration. The investigated resonances are assigned to three different configurations of a positively charged exciton. Together with a singlet ground state and a conventional triplet state (involving an electron from the ground state electronic s-shell), an excited triplet state, which involved an electron from the excited electronic p-shell was identified in single dots. The appearance of an emission line related to the latter complex is due to a partially suppressed electron relaxation in the investigated dots. An analysis of this emission line allows us to scrupulously determine properties of the excited triplet state and compare them with those of the conventional triplet state. Both triplets exhibit similar patterns of anisotropic fine structure and Zeeman splitting, however their amplitudes significantly differ for those two states. Presented results emphasize the role of the symmetry of the electronic state on the properties of the triplet states of two holes + electron excitonic complex.

Efferent Modulation of Stimulus Frequency Otoacoustic Emission Fine Structure.

Otoacoustic emissions, sounds generated in the inner ear, have become a convenient non-invasive tool to examine the efferent modulation of cochlear mechanics. Activation of the medial olivocochlear (MOC) efferents has been shown to alter the magnitude of these emissions. When the effects of efferent activation on the detailed spectral structures of these emissions have been examined, a shift of the spectral patterns toward higher frequencies has been reported for distortion product and spontaneous otoacoustic emissions. Stimulus frequency otoacoustic emissions (SFOAEs) have been proposed as the preferred emission type in the study of efferent modulation due to the simplicity of their production leading to the possibility of clearer interpretation of results. The effects of efferent activation on the complex spectral patterns of SFOAEs have not been examined to the best of our knowledge. We have examined the effects of activating the MOC efferents using broadband noise in normal-hearing humans. The detailed spectral structure of SFOAEs, known as fine structure, was recorded with and without contralateral acoustic stimulation. Results indicate that SFOAEs are reduced in magnitude and their fine structure pushed to higher frequencies by contralateral acoustic stimulation. These changes are similar to those observed in distortion product or spontaneous otoacoustic emissions and behavioral hearing thresholds. Taken together with observations made about magnitude and phase changes in otoacoustic emissions and hearing thresholds upon contralateral acoustic stimulation, all changes in otoacoustic emission and hearing threshold fine structure appear to be driven by a common set of mechanisms. Specifically, frequency shifts in fine structure patterns appear to be linked to changes in SFOAE phase due to contralateral acoustic stimulation.

Mask Design Consideration for Low Aspect Ratio Wet Etch Micromachining on Silicon Substrate Planar Power Transformer

Commercial planar power transformer core majorly inserted manually as stand-alone components sandwiched on the stacked multilayer PCB of the power supply system. The indispensible gap within the layers still seems to produce significant losses due to leakage inductance meanwhile the low thermal conductivity of the PCB worsen the generated heat dispersion process. Thus this paper is to explore a new approach in order to attain a higher efficiency, high thermal conductivity dispersion and low cost mass production on this magnetic device using CMOS development procedure on a silicon wafer substrate. Considerations for the optimum mask design process for power transformer based pattern micromachining on the Silicon substrate process using low cost wet etching process are presented and discussed. The process are to manipule the anisotropy properties using concave and convex mask pattern to produce a correct final angle and pattern using recognized KOH solutions optimized ratio. The conventional wet etching concept has been explored with a several mask design template and comparison between several pattern size in order to attain the best fine structure and correct angle pattern up to 100 um depth. Several convex corner corners compensation methods has been reviewed which finally concluded to method proposed by Wei Fan and Dacheng Zhang has been verified within the 40% KOH:IPA in 50°C solutions experiment.

Synthesis, Structure, and Electron Paramagnetic Resonance Study of a Mixed Valent Metal–Organic Framework Containing Cu2 Paddle-Wheel Units

We report synthesis and composite study of a novel metal–organic framework (MOF) compound of chemical formula ∞3[Cu2ICu2II{H2O}2{(Me–trz–mba)2thio}2]Cl2, where (Me–trz–mba)2thio2– stands for 3,3-(5,5-(thiophene-2,5-diyl)bis(3-methyl-4H-1,2,4-triazole-5,4-diyl))dibenzoate. This coordination polymer was synthesized by solvothermal synthesis. The crystal structure was determined using single crystal X-ray diffraction. The main building block of this compound is a so-called Cu2 paddle-wheel (PW) unit, which contains two Cu2+ ions connected via four carboxylate groups. Magnetic properties of the investigated MOF were studied by continuous-wave electron paramagnetic resonance (EPR) spectroscopy at X- and Q-band frequencies in a wide temperature range. Mononuclear Cu2+ ions were observed in the EPR spectra and characterized by spectral simulations. In addition, the obtained EPR data allowed us to detect and investigate three distinct magnetic interactions related to the Cu2+ pairs. At higher temperatures the fine structure pattern was observed in the EPR spectra and the spin–spin interaction tensor D was determined. The origin of this pattern was assigned to the thermally populated excited triplet states of the Cu2+ pairs. It was found that two Cu2+ ions within a single PW unit couple antiferromagnetically with the exchange coupling constant J = −258 cm–1. Moreover, the EPR spectra of dehydrated MOF samples show a broad, poorly resolved spectral feature, the origin of which is an exchange of the spin triplets between neighboring Cu2 PW units. By simulating the powder pattern of this interdinuclear exchange line, we estimated the exchange coupling between neighboring PW units (|J′| = 4.9 cm–1). It was also found that the interdinuclear exchange gradually disappears, if the dehydrated samples are allowed to interact with air, demonstrating that this exchange can be rather easily manipulated in the investigated MOF.

Effects of contralateral acoustic stimulation on spontaneous otoacoustic emissions and hearing threshold fine structure.

Medial olivocochlear (MOC) influence on cochlear mechanics can be noninvasively, albeit indirectly, explored via the effects of contralateral acoustic stimulation (CAS) on otoacoustic emissions. CAS-mediated effects are particularly pronounced for spontaneous otoacoustic emissions (SOAEs), which are typically reduced in amplitude and shifted upward in frequency by CAS. We investigated whether similar frequency shifts and magnitude reductions were observed behaviorally in the fine structure of pure-tone hearing thresholds, a phenomenon thought to share a common underlying mechanism with SOAEs. In normal-hearing listeners, fine-resolution thresholds were obtained over a narrow frequency range centered on the frequency of an SOAE, both in the absence and presence of 60-dB SPL broadband CAS. While CAS shifted threshold fine structure patterns and SOAEs upward in frequency by a comparable amount, little reduction in the presence or depth of fine structure was observed at frequencies near those of SOAEs. In fact, CAS typically improved thresholds, particularly at threshold minima, and increased fine structure depth when reductions in the amplitude of the associated SOAE were less than 10 dB. Additional measurements made at frequencies distant from SOAEs, or near SOAEs that were more dramatically reduced in amplitude by the CAS, revealed that CAS tended to elevate thresholds and reduce threshold fine structure depth. The results suggest that threshold fine structure is sensitive to MOC-mediated changes in cochlear gain, but that SOAEs complicate the interpretation of threshold measurements at nearby frequencies, perhaps due to masking or other interference effects. Both threshold fine structure and SOAEs may be significant sources of intersubject and intrasubject variability in psychoacoustic investigations of MOC function.

Fine scale spatial genetic structure in Pouteria reticulata (Engl.) Eyma (Sapotaceae), a dioecious, vertebrate dispersed tropical rain forest tree species

Dioecious tropical tree species often have small flowers and fleshy fruits indicative of small-insect pollination and vertebrate seed dispersal. We hypothesize that seed mediated gene flow should be exceed pollen-mediated gene flow in such species, leading to weak patterns of fine scale spatial genetic structure (SGS). In the present study, we characterize novel microsatellite DNA markers and test for SGS in sapling (N=100) and adult trees (N=99) of the dioecious canopy tree Pouteria reticulata (Sapotaceae) in a 50 ha forest dynamics plot on Barro Colorado Island (BCI), Panama. The five genetic markers contained between five and 15 alleles per locus, totaling 51 alleles in the sample population. Significant SGS at local spatial scales (<100m) was detected in the sapling (dbh≈1cm) and adult (dbh≥20cm) size classes, but was stronger in the former (sapling Sp=0.010±0.004, adult Sp=0.006±0.002), suggesting demographic thinning. The degree of SGS was lower than the value expected for non-vertebrate dispersed tropical trees (Sp=0.029), but similar to the average value for vertebrate dispersed tropical trees (Sp=0.009) affirming the dispersal potential of vertebrate dispersed tropical trees in faunally intact forests.

Inter-hydrogen bond coupling in crystals of 3-phenylpyrazole polymorphs investigated by polarized IR spectroscopy

The remarkably strong differences in the fine structure patterns of the νN–H and νN–D bands, temperature and H/D isotopic effects in crystals of two 3-phenylpyrazole (3PhPz) polymorphs, with tetrameric and hexameric hydrogen bond aggregates, were examined by polarized IR spectroscopy, aided by the calculations utilizing the “strong-coupling” model. Experimental and theoretical approaches have suggested that the anti-co-operativity of hydrogen bonds is the main factor responsible for the differences in the spectral properties of both polymorphs. This interaction affects hydrogen-bond geometry of the associates constituting the lattices and in consequence decides about the relative contribution of two different exciton coupling mechanism, “through-space” (SS) and “tail-to-head” (TH), in the spectra generation. The relative contribution of each individual exciton coupling mechanism in the spectra generation is temperature-dependent. In tetramers the TH coupling mechanism dominates at low temperatures, whereas the role of the SS mechanism increases at higher temperatures. For the hexamers the SS mechanism dominates in the wide temperature range. The two types of 3PhPz associates exhibit two different ways of occurring of the H/D isotopic recognition in the crystal hydrogen bonds. In the tetrameric polymorph identical hydrogen isotope atoms exist in entire hydrogen-bonded cycle of 3PhPz. In the case of 3PhPz hexamers, the H/D isotopic recognition mechanism involves pairs of the closely-spaced hydrogen bonds in a cycle.

From Supercomputer Modeling to Highest Mass Resolution in FT-ICR

Understanding of behavior of ion ensembles inside FT-ICR cell based on the computer simulation of ion motion gives rise to the new ideas of cell designs. The recently introduced novel FT-ICR cell based on a Penning ion trap with specially shaped excitation and detection electrodes prevents distortion of ion cyclotron motion phases (normally caused by non-ideal electric trapping fields) by averaging the trapping DC electric field during the ion motion in the ICR cell. Detection times of 5 min resulting in resolving power close to 40,000,000 have been reached for reserpine at m/z 609 at a magnetic field of only 7 Tesla. Fine structures of resolved 13Cn isotopic cluster groups could be measured for molecular masses up to 5.7 kDa (insulin) with resolving power of 4,000,000 at 7 Tesla. Based on resolved fine structure patterns atomic compositions can be directly determined using a new developed algorithm for fine structure processing. Mass spectra of proteins and multimers of proteins reaching masses up to 186 kDa (enolase tetramer) could be measured with isotopic resolution. For instance, at 7 Tesla resolving power of 800,000 was achieved for enolase dimer (96 kDa) and 500,000 for molecular masses above 100 kDa. Experimental data indicate that there is practically no limit for the resolving power of this ICR cell except by collisional damping in the ultrahigh vacuum chamber.

Measurements of dipole and quadrupole polarizabilities of Rn-like Th4+

Measurements of the fine structure pattern in high-$L$, $n$ = 37 Rydberg levels of Th${}^{3+}$ have been extended and improved to allow more precise determinations of the dipole and quadrupole polarizabilities of the Rn-like Th${}^{4+}$ core of the Th${}^{3+}$ Rydberg system. The improved precision is partly due to the recent availability of theoretical calculations that limit the size of higher-order contributions to the fine structure pattern. The measured polarizabilities are ${\ensuremath{\alpha}}_{D}$ = 7.702(6) a.u. and ${\ensuremath{\alpha}}_{Q}$ = 29.1(1.9) a.u.

Effective-potential model for high-LRydberg atoms

A description of fine-structure patterns in nonpenetrating high-$L$ Rydberg atoms and ions is derived in a perturbative model in which the energy denominators occurring in the second-order perturbation theory are evaluated using the adiabatic expansion. The patterns of Rydberg energies that result are dominated by the expectation value of an effective potential containing a range of tensor orders and increasing negative powers of the Rydberg electron's radial coordinate. The coefficients of each term in the effective potential are expressed in terms of matrix elements and energies of the free ion at the core of the Rydberg system. Smaller corrections to these patterns due to application of the effective potential in second order and due to relativistic and spin contributions are also described. The effective potential provides a framework for extracting ion properties from measurements of high-$L$ fine-structure patterns.

Fine Structure in Isotopic Peak Distributions Measured Using a Dynamically Harmonized Fourier Transform Ion Cyclotron Resonance Cell at 7 T

The fine structure of isotopic peak clusters in mass spectra of reserpine and substance P are measured using Fourier transform ion cyclotron resonance mass spectrometry at a 7 T magnetic field. The resolved peaks in the fine structure consist of (13)C, (15)N, (17)O, (18)O, (2)H, (33)S, (34)S, and combinations of them. A recently introduced high-resolution ion cyclotron resonance cell (Nikolaev, E. N.; Boldin, I. A.; Jertz, R.; Baykut, G. J. Am. Soc. Mass Spectrom. 2011, 22, 1125-1133) is used in these experiments. The positions of the experimentally obtained fine structure peaks on the mass scale agree with the isotopic distribution simulations with ≤200 ppb error. Some deviation from the theoretical isotopic distribution is observed, less abundant peaks in the fine structure patterns are a little suppressed compared to the larger ones. We present a method for atomic composition determination using accurate mass data and fine isotopic structure of the mass spectrum. Our method combines the traditional atomic composition determination from accurate mass data by enumeration of all possible formulas within constraints defined a priori with the estimation of element coefficients from resolved isotopic structures. These estimated values allow one to narrow the search space for the composition and therefore to reduce the number of candidate formulas.

Polarized IR Spectra of the Hydrogen Bond in Two Different Oxindole Polymorphs with Cyclic Dimers in Their Lattices

This article focuses on the problem of remarkably strong changes in the fine structure patterns of the ν(N-H) and ν(N-D) bands attributed to the hydrogen and deuterium bonds accompanying the phase transition, which occurs between two polymorphic forms of oxindole. The lattices of these two different crystals contain hydrogen-bonded cyclic dimers differ in their geometry parameters. The source of these differences in the polymorph spectral properties results from the geometry relations concerning the dimers constituting the lattice structural units. In the case of the "alpha" phase, the hydrogen bond lengths of the dimers differ by 0.18 Å. This leads to the "off-resonance exciton coupling" weakly involving the dimer hydrogen bonds. For the "beta" phase, with practically symmetric dimers in the lattice, the spectra become typical for centrosymmetric hydrogen bond systems due to the full resonance of the proton or deuteron vibrations.