Total Transmission Modes Research Articles

Fabrication and structure analysis of freestanding BaTiO3–CeO2 epitaxial nanocomposite membranes

Vertically aligned nanocomposite films hold the promise of making a significant contribution to the performance enhancement and multifunctional integration of flexible thin-film devices but are hindered by the difficulty of direct epitaxial growth on flexible substrates. In this work, freestanding BaTiO3–CeO2 epitaxial nanocomposite membranes were prepared by using water-soluble Sr3Al2O6 as the sacrificial buffer during film deposition. The membrane's lattice parameters as well as their epitaxial relationship, before and after its removal from the single-crystal substrates, were quantitatively measured and analyzed by combining x-ray diffraction and TEM. In addition, synchrotron soft x-ray absorption spectroscopy reveals the discrepancy in the surface and internal electron states of Ce and Ti via comparative studies in total electron yield mode and transmission mode, respectively. This work exemplified that freestanding membranes provide a convenient platform for (1) the study of in-plane lattice information of epitaxial oxide films via TEM and for (2) the comparative study of surface and internal electron band information of epitaxial oxide films.

A novel in situ sample environment setup for combined small angle x-ray scattering (SAXS), wide-angle x-ray scattering (WAXS), and Fourier transform infrared spectrometer (FTIR) simultaneous measurement.

Developing the synchrotron radiation experiment method based on combined technology offers more information on the formation mechanism of new materials and their physical and chemical properties. In this study, a new small-angle x-ray scattering/ wide-angle x-ray scattering/ Fourier-transform infrared spectroscopy (SAXS/WAXS/FTIR) combined setup was established. Using this combined SAXS/WAXS/FTIR setup, x-ray and FTIR signals can be obtained simultaneously from the same sample. The in situ sample cell was designed to couple two FTIR optical paths for the attenuated total reflection and transmission modes, which greatly saved the time of adjusting and aligning the external infrared light path when switching between the two modes with good accuracy. A transistor-transistor logic circuit was used to trigger the synchronous acquisition from the IR and x-ray detectors. A special sample stage is designed, allowing access by the IR and x-ray with temperature and pressure control. The newly developed, combined setup can be used to observe the evolution of the microstructure during the synthesis of composite materials in real-time at both the atomic and molecular levels. The crystallization of polyvinylidene fluoride (PVDF) at different temperatures was observed. The time-dependent experimental data demonstrated the success of the in situ SAXS, WAXS, and FTIR study of the structural evolution, which is feasible to track the dynamic processes.

New total transmission modes of the Kerr geometry with Schwarzschild limit frequencies at complex infinity

In addition to the well-known quasinormal modes, the gravitational modes of the Kerr geometry also include sets of total-transmission modes. Each mode can be considered as an element of a sequence of modes parameterized by the angular momentum of the black hole. One family of gravitational total-transmission modes of Kerr have been known for some time. Modes in this family connect to a Schwarzschild limit where the mode frequency is finite and purely imaginary. Recently, what was thought to be an additional branch of this original family of modes was discovered. However, this new branch is actually a part of one of two entirely new families of total-transmission modes. Modes in these new families, surprisingly, connect to a Schwarzschild limit where the mode frequencies exist at complex infinity. We have numerically constructed full sets of sequences of gravitational total-transmission modes for harmonic indices $\ell=[2,8]$. Using these numerical sequences, we have been able to construct analytic asymptotic expansions for the mode frequencies and their associated separation constants. The asymptotic expansion for the separation constant used in constructing the total-transmission modes seems to be valid for general complex values of the oblateness parameter.

Analysis of coextruded polyethylene-based packaging films: number of layers, composition, and mechanical properties

Five coextruded and one blown polyethylene (PE)-based packaging films were analyzed with the aim to determine the number and thickness of the film layers and tensile mechanical properties and to prove composition declared by a producer. They were chosen the most effective methods such as Fourier-transform infrared spectroscopy (attenuated total reflectance and transmission modes), differential scanning calorimetry (DSC), thermogravimetry, wide-angle X-ray diffraction (XRD), and confocal laser scanning microscopy. The latter turned out to be very effective method to show the film layers on its fracture surfaces due to very good contrast and different fracture patterns of each layer. Two to five layers were detected in the films, whereas silicone surface layer with the thickness not higher than 1 µm was very nicely detected in two coextruded films. The type of PE (low density, linear low density and high density) was determined by DSC, whereas miscible types of PE were differentiated only after performance of stepwise isothermal crystallization. This was performed in case of four films at 124, 114, 104, and 94 °C with 30-min dwell at each temperature. Random copolymer of polypropylene was identified by DSC in two films. Infrared spectroscopy revealed polymers present in low content (ethylene–vinyl acetate and silicon) and, in addition, additives such as calcite, which was detected also by XRD. The major polymer components were proved in four films. Mechanical properties varied in machine and transverse direction in case of all films. The methods used are also recommended for quality control of coextruded films.

Unknown branch of the total-transmission modes for the Kerr geometry

The gravitational modes of the Kerr geometry include both quasinormal modes and total-transmission modes. Sequences of these modes are parameterized by the angular momentum of the black hole. The quasinormal and total-transmission modes are usually distinct, having mode frequencies that are different at any given value of the angular momentum. But a discrete and countably infinite subset of the left-total-transmission modes are simultaneously quasinormal modes. Most of these special modes exist along previously unknown branches of the gravitational total-transmission modes. In this paper, we give detailed plots of the total-transmission modes for harmonic indices $\ell=[2,7]$, with special emphasis given to the $m=0$ modes which all contain previously unknown branches. All of these unknown branches have purely imaginary mode frequencies. We find that as we approach the Schwarzschild limit along these new branches, the mode frequencies approach $-i\infty$ in stark contrast to the finite mode frequency obtained in the Schwarzschild limit along the previously known branches. We explain when and why, at certain frequencies, the left-total-transmission modes are simultaneously quasinormal modes. At these same frequencies, the right-total-transmission modes are missing. We also derive analytic expressions for the asymptotic behavior of the total-transmission mode frequencies, and for the values of the angular momentum at which the modes are simultaneously quasinormal modes.

Investigation of oil distribution in spray-dried chia seed oil microcapsules using synchrotron-FTIR microspectroscopy

In this study, chia seed oil (CSO) microcapsules were produced using three types of shell materials, including chia seed protein (CPI), chia seed gum (CSG) and CPI-CSG complex coacervates. Synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy was used to investigate the effect of shell materials on the distribution of CSO both on the surface and in the interior of the solid microcapsules. S-FTIR measurements were carried out in macroscopic attenuated total reflection (macro ATR) and transmission modes, to determine the surface lipid and the encapsulated lipid fractions, respectively. The amounts of lipid and protein distributed on the surface and in the interior of the microcapsules were compared based on the average spectra extracted from S-FTIR chemical images obtained from each type of the microcapsules. The unsaturated fatty acids (UFAs) to total oil ratios in all the three types of the microcapsules were closely similar to the original non-processed CSO, suggesting an effective encapsulation and thereby shielding protection of UFAs from oxidative damage during microencapsulation process. The type of the shell materials was found to affect the distribution of CSO on the surface and within the microcapsules. The complex coacervation based microcapsules had a significantly lower oil content (∼2% w/w) on the surface compared to those observed for the other two types of microcapsules (>5%, w/w).

Modes of the Kerr geometry with purely imaginary frequencies

In this paper, we examine the behavior of modes of the Kerr geometry when the mode's frequency is purely imaginary. We demonstrate that quasinormal modes must be polynomial in nature if their frequency is purely imaginary, and present a method for computing such modes. The nature of these modes, however, is not always easy to determine. Some of the polynomial modes we compute are quasinormal modes. However, some are simultaneously quasinormal modes and total transmission modes, while others fail to satisfy the requisite boundary conditions for either. This analysis is, in part, an extension of the results known for Schwarzschild black holes, but clarifies misconceptions for the behavior of modes when the black hole has angular momentum. We also show that the algebraically special modes of Kerr with m=0 have an additional branch of solutions not seen before in the literature. All of these results are in precise agreement with new numerical solutions for sequences of gravitational quasinormal modes of Kerr. However, we show that some prior numerical and analytic results concerning the existence of quasinormal modes of Kerr with purely imaginary frequencies were incorrect.

Acoustic total transmission and additional modes in the metamaterials embedded with defects

Total reflection or transmission of waves has been explored extensively in different types of zero-index metamaterials (ZIMs). Almost all previous studies have shown that only monopole modes are excited inside the defects if they are cylindrical. However, the underlying physics for excited modes inside defects is wrongly ignored. In this work, we reveal that there is not only a monopole mode but also additional higher modes excited inside cylindrical defects by a system of two-dimensional waveguides. Actually, the total acoustic transmission and additional higher modes can occur simultaneously in a ZIM waveguide embedded with defects. We reveal the physical mechanism of excited higher modes, which will perfect the current perception of the excited modes in the acoustic metamaterials inside defects. Moreover, numerical simulations are carried out to demonstrate our finding concerning the additional modes.

Gravitational perturbations of the Kerr geometry: High-accuracy study

We present results from a new code for computing gravitational perturbations of the Kerr geometry. This new code carefully maintains high precision to allow us to obtain high-accuracy solutions for the gravitational quasinormal modes of the Kerr space-time. Part of this new code is an implementation of a spectral method for solving the angular Teukolsky equation that, to our knowledge, has not been used before for determining quasinormal modes. We focus our attention on two main areas. First, we explore the behavior of these quasinormal modes in the extreme limit of Kerr, where the frequency of certain modes approaches accumulation points on the real axis. We compare our results with recent analytic predictions of the behavior of these modes near the accumulation points and find good agreement. Second, we explore the behavior of solutions of modes that approach the special frequency $M\omega=-2i$ in the Schwarzschild limit. Our high-accuracy methods allow us to more closely approach the Schwarzschild limit than was possible with previous numerical studies. Unlike previous work, we find excellent agreement with analytic predictions of the behavior near this special frequency. We include a detailed description of our methods, and make use of the theory of confluent Heun differential equations throughout. In particular, we make use of confluent Heun polynomials to help shed some light on the controversy of the existence, or not, of quasinormal and total-transmission modes at certain special frequencies in the Schwarzschild limit.

Calculation of leaky Lamb waves with a semi-analytical finite element method

A semi-analytical finite element method (SAFE) has been widely used for calculating dispersion curves and mode shapes of guided waves as well as transient waves in a bar like structures. Although guided wave inspection is often conducted for water-loaded plates and pipes, most of the SAFE techniques have not been extended to a plate with leaky media. This study describes leaky Lamb wave calculation with the SAFE. We formulated a new solution using a feature that a single Lamb wave mode generates a harmonic plane wave in leaky media. Dispersion curves obtained with the SAFE agreed well with the previous theoretical studies, which represents that the SAFE calculation was conducted with sufficient accuracy. Moreover, we discussed dispersion curves, attenuation curves, and displacement distributions for total transmission modes and leaky plate modes in a single side and both two side water-loaded plate.

In-Line Monitoring of Bacteria in Drinking Water By Infrared Spectroscopy and Micro-Flow Cytometry

Water from a municipal network water supply is stored in tanks and then pumped to tanks in tall buildings, which is so called “second water supply”. However, the water stored in tanks provides the potential environment for bacteria to grow and multiply. It is labor and time-consuming to routinely and frequently sample water from the water tanks distributed in a city, and to test all samples by biological methods in labs, which thus restricts the detection and prevention of water-borne diseases. Therefore, a rapid and low-cost method1,2 is urgently needed to routinely and automatically monitor and report the bacterial level in water tanks, allowing for taking appropriate actions in time. Infrared (IR) spectroscopy is a powerful tool for characterization and identification of micro-organisms because of its sensitivity and specificity, speed, and potential for automation. Microorganisms have unique “fingerprint” spectral features in the mid-infrared (MIR) range. Therefore, IR spectroscopy is a feasible technique for the identification of unknown bacterial samples based on the pre-established bacterial spectrum libraries. There are mainly two modes in IR spectroscopy to obtain the IR spectrum of bacteria in water - attenuated total reflection (ATR) and transmission modes. The first mode has been used by many researchers previously because it could avoid the influence of water on the bacterial spectrum, which has three strong absorption bands in the range of 400 to 4000 cm-1. However, the ATR technique lacks the ability to provide spectral data for quantitative analysis because the spectrum acquired in ATR mode is dependent on the thickness and density of the bacterial film formed on the outer surfaces of the ATR crystal. Therefore the transmission mode of FTIR is used in this research. Three strains of two species, E.coli K-12 MG1655 and E.coli K-12 HS2210 from Ecoli and Staphylococcus aureus (ATCC 25923) were placed directly into double distilled water. Then, the CaF2 cuvette containing bacteria suspention with different concentrations were used to obtain the IR spectra using a Vertex v80 FTIR spectrometer. Ultra-high concentrations of bacteria over 1010 cells/ml are used to guarantee enough changes in absorption between double distilled water and samples. Time-resoved IR spectra of E.coli K-12 MG1655 shows that its spectrum varies slightly within one hour. Obvious differences were observed in the spectra of E.coli K-12 MG1655 and Staphylococcus aureus (ATCC 25923), which shows the specificity on the IR spectrum of different species. However, similar differences were not found between E.coli K-12 MG1655 and HS2210. In addition, the intensity of the absorption peaks in the spectra of all the three strains is proportional to the concentration of the samples.Because of limitation of FTIR spectroscopy on quantifying bacteria accurately, a photonic-microfluidic integrated device based flow cytometer3-5 is incorporated into the monitoring system to ensure reliable estimation of bacterial concentration. The functionality layer of the device including input and output waveguides, lens systems and microfluidic channels is fabricated by patterning SU-8 photoresist using photolithography, which is actually supported by a pyrex glass substrate and covered by a PDMS covering layer with holes aligned with all the inlets and outlet. Light from a laser is directed into the input waveguide of the device through an optic fiber, then focused to the center of the microfluidic channel by a lens system, where the bacteria will be interrogated. Bacterial suspension in a syringe is injected to the sample inlet by a syringe pump and hydro-focused into the center of microfluidic channel by the sheath flows at both sides. Scattered light produced by bacteria passing through the focused light beam will be collected by the objective and filtered by an optic filter with passband of 525-535 nm. A photomultiplier tube is used to detect, convert and amplify the light signals into current signals, which will be further amplified into votage singals by a current to voltage amplifier. Voltages signals will be digitized by a data acqusition card and recorded by a custom LabView program for data analysis.The performance of flow cytometer based on the integrated devices with different beam shaping lens systems was calibrated by detecting scattered light from 1µm-diameter blank polystyrene beads running through the device. Due to uniform geometry, size and material, the device yielding minimal coefficient of variation (CV) will be the best for applications.Enumeration of E.coli in phosphate-buffered saline was carried out to validate the accuracy of counting bacteria using this micro-chip based flow cytometer. A 92% of detection efficiency was achieved. Expanded population of distribution of E. coli counting than beads counting was found because of the more flexibility of scattering light by rod-shape of E.coli than sphere-shape of beads as well as the natural size variation of E. coli. Tests on mixture of E.coli and 2µm, 4 µm beads show distinct separation of the population distribution, confirming the ability to differentiate E.coli from larger size inorganic particles by scattering intensity.

The transition from the native to the acid-state characterized by multi-spectroscopy approach: Study for the holo-form of bovine α-lactalbumin

The transition of the holo-form of bovine α-lactalbumin from the native (N) to the pH-generated acidic-state (A-state) was analyzed by probing its tertiary and secondary structure using a concerted spectroscopic approach combining near- and far-UV circular dichroism (CD), electrospray ionization ion mobility mass spectrometry (ESI-IM-MS), vibrational circular dichroism (VCD), and Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflection (ATR) and transmission (TR) modes. The spectroscopic results, which relied on the interaction of an electromagnetic field with different molecular targets, confirmed the decay of extensive rigid side-chain packing interactions during the pH-induced N→A-state transition and revealed the targets' dependence on secondary structural changes. Independent analyses of the spectral changes using two methods of multivariate analysis, such as principal component analysis and two-dimensional correlation spectroscopy, revealed small but significant differences in the secondary structure as a result of the all-or-none transition. The cooperativity of the transition was quantitatively described using values corresponding to the mid-point (tm) and width of the transition (Δtm). The averages of the two parameters, calculated using the data collected by the different probes, were equal to 3.5±0.2 and 0.6±0.1(SE), respectively. The variable two-state nature of the cooperative N→A-state transition confirmed that the protonation of the side chain carboxyl groups on the Asp and Glu residues and that the release of a Ca2+ ion induced structural changes on both the secondary and tertiary levels. The changes have been confirmed by results obtained from the concerted spectroscopic approach.

QUANTIZATION OF ENTROPY SPECTRA OF BLACK HOLES

From the quasinormal modes (QNM) of black holes, we obtain the quantizations of the entropy and horizon area of black holes via Bohr–Sommerfeld quantization, based on Bohr's correspondence principle. For this, we identify the appropriate action variable of the classical system corresponding to a black hole. By considering the BTZ black holes in topologically massive gravity as well as Einstein gravity, it is found that the spectra of not the horizon areas but the entropies of black holes are equally spaced. We also propose that other characteristic modes of black holes, which are non-QNM or holographic QNM, can be used in quantization of entropy spectra just like QNM. From these modes, it is found that only the entropy spectrum of the warped AdS3 black hole is equally spaced as well. Furthermore, by considering a scattering problem in a black hole, we propose that the total transmission modes and total reflection modes of black holes can be regarded as characteristic modes of black holes and result in the equally spaced entropy of the Kerr and Reissner–Nordström black holes. Finally, we conclude that there is a universal behavior that the entropy spectra of various black holes are equally spaced.

Thickness and angular dependence of the L‐edge X‐ray absorption of nickel thin films

We report on the near‐edge X‐ray absorption fine structure spectroscopy of the L3 (2p3/2) and L2 (2p1/2) edges for ferromagnetic pure nickel transition metal and show that the L2,3 edge peak intensity and satellite feature at ~6 eV above the L3 edge in nickel increase with increasing nickel film thickness both in the total electron yield and transmission modes. The absorption spectra of nickel metal, however, exhibit strong angular‐dependent effects when measured in total electron yield mode. In addition, we calculated the mean electron escape depth of the emitted electrons (λe), which was found for pure nickel metal to be λe=25 ± 2 Å. We point out the advantages of the total electron yield technique for the study of the L‐edge of 3d transition metals. Copyright © 2011 John Wiley & Sons, Ltd.

Chemical changes in PMMA as a function of depth due to proton beam irradiation

In this work we determined depth profiles of the chemical change in PMMA irradiated with 2 MeV protons by infrared spectroscopic and micro-Raman measurements. The measurements were carried out on 10 μm thin stacked foil samples using an infrared spectrometer in universal attenuated total reflectance (UATR) and transmission modes; while the thick samples were analyzed with a confocal micro-Raman spectrometer. The depth profiles of the changes formed due to the various delivered fluences were compared to each other. The measurements show the strong dependence of the degree of modification on the energy transfer from the decelerating protons. Depth profiles reveal that at the fluences applied in this work the entire irradiated volume suffered some chemical modifications. In case of low-fluence samples the zone of maximal modification is restricted only to the Bragg peak, but with increasing fluences the region of maximal modification extends towards the sample surface.

Entropy spectra of black holes from resonance modes in scattering by the black holes

Since Bekenstein's proposal that a black hole has an equally spaced area spectrum, the quasinormal modes (QNM) as the characteristic modes of a black hole have been used for obtaining the horizon area spectrum of the black hole. However, the area spectrum of the Kerr black hole in some previous works was inconsistent with Bekenstein's proposal. In this paper, noting that black holes can have three types of resonance modes which are QNM, total transmission modes (TTM), and total reflection modes (TRM), we propose that all of these modes in a highly damped regime should be used in quantizing the black hole. Although the QNM and the TTM of the Kerr black hole give us complicated quantization conditions from the Bohr–Sommerfeld quantization of an action variable, we find a very simple result from the TRM. It gives an equally spaced outer horizon area. Therefore, by the Bekenstein–Hawking area law, we find that the Kerr black hole has universal behavior of the equally spaced entropy spectrum. With the same argument, we find that the Reissner–Nordström black hole also has the equally spaced entropy spectrum.

Heart Rate Wireless Monitoring System “Cardiobeat”, Novel Approach to ECG Processing and Representation

The paper concerns the development of the heart rate wearable wireless monitoring system “CardioBeat”. This system has two types of transmission mode, which are total signal transmission and heart rate transmission modes. The developed system uses wireless PAN (Personal Area Network), which operates in low-power mode. It is composed of two main parts: ECG registering circuit with wireless communication module and base station with terminal. The registering circuit has three surface electrodes, ECG amplifier and microcontroller. In total signal transmission mode, it can send data with transmission speed corresponding up to 300 ECG samples per second. In heart rate transmission mode, it can calculate heart rate from ECG data with 300 samples per second and send packets at the specified rate. Base station communication unit forwards the received data to PC, where the data can be stored and displayed. The developed equipment showed the possibility of real-time monitoring of the patients in their daily life and is expected to contribute, in particular, to the saving of medical expenses.

Structural and magnetic deconvolution of FePt/FeOx-nanoparticles using x-ray magnetic circular dichroism

Recently, magnetite nanoparticles have attracted much attention, due to their technological potential based on different optic, magnetic and catalytic sections. In particular, the magnetic properties of hybrid nanocrystals can be tailored by the combination of complementary magnetic materials like for example magnetite and FePt. In order to analyse the related magnetic and structural properties of the resulting bi-component systems, we present x-ray absorption and x-ray magnetic circular dichroism studies at the Fe L2,3 edges simultaneously performed in total electron yield and transmission mode, done at room and low temperatures. This provides in particular the separation of volume- and surface-related properties. The investigated system was made up of FePt/FeOx hybrid nanocrystals, which could be uniquely tuned in size and volume ratios. These measurements have been combined with magnetometry and high-resolution transmission electron microscopy studies. The separation between surface and bulk has been done by a deconvolution of the absorption spectra in terms of a linear superposition of reference spectra. With this universally applicable technique we are able to experimentally determine that the outer FeOx shell fraction at the surface has a strongly reduced magnetization and is of maghemite character, while the inner part is more magnetite like. So the technique shown here can be used to characterize nanoparticular systems and determine their structural and magnetic properties.

Asymptotic spectroscopy of rotating black holes

We calculate analytically the transmission and reflection amplitudes for waves incident on a rotating black hole in d=4, analytically continued to asymptotically large, nearly imaginary frequency. These amplitudes determine the asymptotic resonant frequencies of the black hole, including quasinormal modes, total-transmission modes and total-reflection modes. We identify these modes with semiclassical bound states of a one-dimensional Schroedinger equation, localized along contours in the complexified r-plane which connect turning points of corresponding null geodesics. Each family of modes has a characteristic temperature and chemical potential. The relations between them provide hints about the microscopic description of the black hole in this asymptotic regime.

Diffusion and Structure of Water in Polymers Containing N-Vinyl-2-pyrrolidone

Poly(N-vinyl-2-pyrrolidone) (PVP), a water-soluble polymer, is known for its excellent biocompatibility. It is generally recognized that the properties of polymers may be profoundly affected by the structure of water absorbed in them. In this study, Fourier transform infrared (FT-IR) in attenuated total reflection (ATR) and transmission mode was performed to examine the diffusion and structure of water in PVP and its copolymers. The obtained spectra were analyzed using two-dimensional (2D) IR with the aid of density functional theory (DFT) calculations. The 2D IR of time-resolved FT-IR/ATR spectra shows that type II water between 3300 and 3500 cm(-1) occurs earlier during the water absorption process, which is also demonstrated by transmission FT-IR at the initial stage of water absorption. Conversely, type II water changes last when desorption takes place. Results from DFT calculations indicate that type II water might be monomeric or dimeric water molecules interacting with a carbonyl group in the pyrrolidone moiety. Furthermore, it is found that vibrations less than 3300 cm(-1) (type I water) arise from water molecules involved in a carbonyl group interacting with more than two water molecules. It is reasonable that the transmission FT-IR spectra of film with an extra low water amount hardly show vibration bands below 3300 cm(-1); however, this region is distinct in the FT-IR/ATR spectra of fully swollen film. In addition, vibration bands between 3800 and 3500 cm(-1) (type III water) are assigned to free water or water with relatively weak hydrogen bonding, as supported by the transmission FT-IR spectra of polyacrylonitrile (PAN) and the calculation results. Therefore, the diffusion process and the structures of water in PVP and its copolymers can be successfully accessed on the basis of the 2D IR analysis and DFT calculations.