Principal Spectral Components Research Articles

Evaluation of an Integrated Spectroscopy and Classification Platform for Point-of-Care Core Needle Biopsy Assessment: Performance Characteristics from Ex Vivo Renal Mass Biopsies

PurposeTo evaluate a transmission optical spectroscopy instrument for rapid ex vivo assessment of core needle cancer biopsies (CNBs) at the point of care. Materials and MethodsCNBs from surgically resected renal tumors and nontumor regions were scanned on their sampling trays with a custom spectroscopy instrument. After extracting principal spectral components, machine learning was used to train logistic regression, support vector machines, and random decision forest (RF) classifiers on 80% of randomized and stratified data. The algorithms were evaluated on the remaining 20% of the data set held out during training. Binary classification (tumor/nontumor) was performed based on a decision threshold. Multinomial classification was also performed to differentiate between the subtypes of renal cell carcinoma (RCC) and account for potential confounding effects from fat, blood, and necrotic tissue. Classifiers were compared based on sensitivity, specificity, and positive predictive value (PPV) relative to a histopathologic standard. ResultsA total of 545 CNBs from 102 patients were analyzed, yielding 5,583 spectra after outlier exclusion. At the individual spectra level, the best performing algorithm was RF with sensitivities of 96% and 92% and specificities of 90% and 89%, for the binary and multiclass analyses, respectively. At the full CNB level, RF algorithm also showed the highest sensitivity and specificity (93% and 91%, respectively). For RCC subtypes, the highest sensitivity and PPV were attained for clear cell (93.5%) and chromophobe (98.2%) subtypes, respectively. ConclusionsEx vivo spectroscopy imaging paired with machine learning can accurately characterize renal mass CNB at the time of tissue acquisition.

Comparison of signal decomposition techniques for analysis of human cortical signals

Objective. Conventional neural signal analysis methods assume that features of interest are linear, time-invariant signals confined to well-delineated spectral bands. However, new evidence suggests that neural signals exhibit important non-stationary characteristics with ill-defined spectral distributions. These features pose a need for signal processing algorithms that can characterize temporal and spectral features of non-linear time series. This study compares the effectiveness of four algorithms in extracting neural information for use in decoding cortical signals: Fast Fourier Transform bandpass filtering (FFT), principal spectral component analysis (PSCA), wavelet analysis (WA), and empirical mode decomposition (EMD). Approach. Electrocorticographic signals were recorded from the motor and sensory cortex of two epileptic patients performing finger movements. Each signal processing algorithm was used to extract beta (10–30 Hz) and gamma (66–114 Hz) band power to detect thumb movement and decode finger flexions, respectively. Naïve-Bayes (NB), support vector machine (SVM), and linear discriminant analysis (LDA) classifiers using each signal were validated using leave-one-out cross-validation. Main results. Decoders using all four signal decompositions achieved above 90% average accuracy in finger movement detection using beta power. When decoding individual finger flexion using gamma, the PSCA NB classifiers achieved 78 ± 4% accuracy while FFT, WA, and EMD analysis achieved accuracies of 73 ± 8%, 68 ± 7%, and 62 ± 3% respectively, with similar results using SVM and LDA. Significance. These results illustrate the relative levels of useful information contributed by each decomposition method in the case of finger movement decoding, which can inform the development of effective neural decoding pipelines. Further analyses could compare performance using more specific non-sinusoidal features, such as transients and phase-amplitude coupling.

On exact Hausdorff measure functions of operator semistable Lévy processes

ABSTRACTLet X = {X(t)}t ⩾ 0 be an operator semistable Lévy process on with exponent E, where E is an invertible linear operator on . In this article, we determine exact Hausdorff measure functions for the range of X over the time interval [0, 1] under certain assumptions on the principal spectral component of E. As a byproduct, we also present Tauberian results for semistable subordinators and sharp bounds for the asymptotic behavior of the expected sojourn times of X.

Application of the constant stoichiometry grouping concept to the Raman spectra of Pb(PO 3) 2-TeO 2 glasses

Pb(PO 3) 2-TeO 2 glasses in the whole range of glass composition were first obtained and their properties (refractive index, density, T g and light scattering losses) were determined. Based on the vibrational spectroscopy data a new approach was applied to investigate the interactions of initial oxides in melts resulted in so-called constant stoichiometry groupings (CSGs) formation symbolizing intermediate range order in glasses. Vibrational spectra of glasses are interpreted as a superposition of unchangeable spectral forms (principal spectral components (PSCs)) belonging to CSGs: PbO · P 2O 5, TeO 2 · 2PbO · 2P 2O 5, TeO 2 · PbO · P 2O 5, TeO 2, and possibly 2TeO 2 · PbO · P 2O 5 and 6TeO 2 · PbO · P 2O 5. In this work Multivariate Data Analysis has been applied as the independent mathematical tool to decompose Raman spectra of glasses and reveal the number of PSCs. It is shown that application of factor analysis results in the same five PSCs that confirms our data obtained from the CSG concept. This concept allows also the prediction of the existence of unknown compounds, and correspondingly some crystals (TeO 2⋅ 2PbO⋅2P 2O 5 and others) were revealed by XRPD of the crystallized glasses. The CSG concept opens the way for elaboration of low scattering glasses as candidates for Raman amplifiers. It is shown that Pb(PO 3) 2-TeO 2 glasses with small content of TeO 2 are of interest to photonic technology.

Forensic body fluid identification: The Raman spectroscopic signature of saliva

The potential use of Raman spectroscopy for nondestructive, confirmatory identification of body fluids at the crime scene has been reported recently (Virkler and Lednev, Forensic Sci.,Int., 2008, 181, e1-e5). However, those experiments were performed using only one sample of each body fluid and did not investigate the potential for spectral variations among different donors of the same fluid. This paper reports on the role of heterogeneity within a single human saliva sample as well as among samples from multiple donors. Near-infrared (NIR) Raman spectroscopy was used to measure spectra of pure dried human saliva samples from multiple donors in a controlled laboratory environment. Principal component analysis of spectra obtained from multiple spots on dry samples showed that dry saliva is heterogeneous and its Raman spectra could be presented as a linear combination of a fluorescent background and three spectral components. The major chemical components known to be present in saliva were used to tentatively identify the principal spectral components. The issue of potential spectral variations that could arise between different donors of saliva was also addressed. The relative contribution of each of the three components varies with donor, so no single spectrum could effectively represent an experimental Raman spectrum of dry saliva in a quantitative way. The combination of these three spectral components could be considered to be a spectroscopic signature for saliva. This proof of concept approach shows the potential for Raman spectroscopy to identify an unknown substance to be saliva during forensic analysis.

Raman spectroscopic signature of semen and its potential application to forensic body fluid identification

A great potential of Raman spectroscopy for non-destructive, confirmatory identification of body fluids at the crime scene has been reported recently (Virkler and Lednev, Forensic Sci. Int. 2008 [5]). However, that analysis was carried out on only one sample of each body fluid and did not take into account any variations that might occur between different donors of the same fluid. This paper reports on the role of heterogeneity within a sample as well as among multiple donors for human semen. Near-infrared (NIR) Raman spectroscopy was used to measure spectra of pure dried human semen samples from multiple donors in a controlled laboratory environment. The major chemical components that contributed to the Raman spectrum of semen were determined and used to tentatively identify the principal spectral components. The issue of potential spectral variations that could arise between different donors of semen was also addressed. Advanced statistical analysis of spectra obtained from multiple spots on dry samples showed that dry semen is heterogeneous and its Raman spectra could be presented as a linear combination of a fluorescent background and three spectral components. The relative contribution of each of the three components varies with donor, so no single spectrum could effectively represent an experimental Raman spectrum of dry semen in a quantitative way. The combination of the three spectral components could be considered to be a spectroscopic signature for semen. This proof-of-concept approach shows the potential for Raman spectroscopy to identify an unknown substance to be semen during forensic analysis.

Evaluating the principal spectral components positioning a virtual sound source on a cone of confusion

Although many studies have attempted to identify spectral cues to sound-source direction for the entire sphere of possible incidence angles, few studies have focused their attention on directional hearing for virtual sources positioned on cones of confusion. These regions of space, defined by relatively constant interaural time and intensity differences, provide an ideal subset of incidence angles for testing the importance of the spectral cues to direction allowing for up/down and front/rear distinctions between sources at constant angular distance from the median plane. In this study, head-related transfer functions (HRTFs) measured on a well-lateralized cone of confusion were decomposed into principal spectral components putatively responsible for positioning a virtual sound source, and their related angle-dependent scores that describe the relative contribution of each shape to the total spectral variation. The findings can be summarized as follows: For the set of ipsilateral HRTFs the most significant set of scores shows sinusoidal variation with angle, and could potentially encode a front-back cue, though with the extrema rotated by about 30 deg. The most significant score from an analysis of interaural spectral differences seems to capture a head-shadowing effect which is most extreme in the lower rear.

04/00969 Effect of water vapor on tritium release from ceramic breeder material: Munakata, K. et al. Fusion Engineering and Design, 2003, 69, (1–4), 27–31

Pb(PO3)2-TeO2 glasses in the whole range of glass composition were first obtained and their properties (refractive index, density, Tg and light scattering losses) were determined. Based on the vibrational spectroscopy data a new approach was applied to investigate the interactions of initial oxides in melts resulted in so-called constant stoichiometry groupings (CSGs) formation symbolizing intermediate range order in glasses. Vibrational spectra of glasses are interpreted as a superposition of unchangeable spectral forms (principal spectral components (PSCs)) belonging to CSGs: PbO · P2O5, TeO2 · 2PbO · 2P2O5, TeO2 · PbO · P2O5, TeO2, and possibly 2TeO2 · PbO · P2O5 and 6TeO2 · PbO · P2O5. In this work Multivariate Data Analysis has been applied as the independent mathematical tool to decompose Raman spectra of glasses and reveal the number of PSCs. It is shown that application of factor analysis results in the same five PSCs that confirms our data obtained from the CSG concept. This concept allows also the prediction of the existence of unknown compounds, and correspondingly some crystals (TeO2⋅ 2PbO⋅2P2O5 and others) were revealed by XRPD of the crystallized glasses. The CSG concept opens the way for elaboration of low scattering glasses as candidates for Raman amplifiers. It is shown that Pb(PO3)2-TeO2 glasses with small content of TeO2 are of interest to photonic technology.

Fine structure of the low-frequency spectra of heart rate and blood pressure.

BackgroundThe aim of this study was to explore the principal frequency components of the heart rate and blood pressure variability in the low frequency (LF) and very low frequency (VLF) band. The spectral composition of the R–R interval (RRI) and systolic arterial blood pressure (SAP) in the frequency range below 0.15 Hz were carefully analyzed using three different spectral methods: Fast Fourier transform (FFT), Wigner-Ville distribution (WVD), and autoregression (AR). All spectral methods were used to create time–frequency plots to uncover the principal spectral components that are least dependent on time. The accurate frequencies of these components were calculated from the pole decomposition of the AR spectral density after determining the optimal model order – the most crucial factor when using this method – with the help of FFT and WVD methods.ResultsSpectral analysis of the RRI and SAP of 12 healthy subjects revealed that there are always at least three spectral components below 0.15 Hz. The three principal frequency components are 0.026 ± 0.003 (mean ± SD) Hz, 0.076 ± 0.012 Hz, and 0.117 ± 0.016 Hz. These principal components vary only slightly over time. FFT-based coherence and phase-function analysis suggests that the second and third components are related to the baroreflex control of blood pressure, since the phase difference between SAP and RRI was negative and almost constant, whereas the origin of the first component is different since no clear SAP–RRI phase relationship was found.ConclusionThe above data indicate that spontaneous fluctuations in heart rate and blood pressure within the standard low-frequency range of 0.04–0.15 Hz typically occur at two frequency components rather than only at one as widely believed, and these components are not harmonically related. This new observation in humans can help explain divergent results in the literature concerning spontaneous low-frequency oscillations. It also raises methodological and computational questions regarding the usability and validity of the low-frequency spectral band when estimating sympathetic activity and baroreflex gain.

The Use of SAR to Measure Ocean Wave Dispersion in Frazil–Pancake Icefields

Abstract Icefields composed of frazil and pancake ice play important roles in both polar regions in winter. During the early to midwinter period pancake ice is a major component of the Antarctic sea ice cover, while in the Arctic the Odden ice tongue in the Greenland Sea, associated with deep convection, is composed mainly of pancake ice. The retrieval of sea ice thickness by remote sensing is, in general, a very difficult task. In this paper the change in dispersion of ocean waves as they penetrate into pancake ice is considered so as to gain insight into its possible relationship with thickness. Spectral analysis of subscenes from ERS-2 (second European Remote Sensing Satellite) synthetic aperture radar (SAR) images yields the wavelength and direction of the principal spectral component both outside and inside the ice cover. There is a decrease of wavelength at the ice edge, as well as refraction toward the normal and a loss of amplitude. The analysis is complex because the true wave spectrum must be re...

Extra Ocular Photic Entrainment in Drosophila Melanogaster

The ability to anticipate the daily changes occurring in the photic environment, by adjusting their physiology and behavior accordingly, should provide living organisms with a selective advantage. Organisms could thus sample the relevant entraining stimuli at early dawn and/or late dusk. At these times of the day the principal spectral components of sunlight reaching the Earth's surface consist of relatively low levels of irradiance in the blue and red parts of the visible spectrum. Biological circadian systems could entrain to twilight conditions by sampling either one or both of these components. Previous studies, based on the characterization of phase response curves, following brief exposures to relatively high intensity light of varying wavelength, demonstrated the particular sensitivity of the Drosophila circadian system to blue light. In this study, we addressed the capacity of the circadian system of Drosophila to respond to long periods of exposure to red light. Thus flies were initially exposed to 12 h : 12 h LD cycles with full spectrum white light. Following a 1–4 h phase shift, the flies were exposed to LD cycles with red light. Our results suggest that, under these experimental conditions, red light of wavelength between 650–700 nm, can function as an entraining stimulus. Furthermore, analysis of the circadian locomotor activity profiles in visually impaired flies, suggests that in wild type flies locomotor activity is triggered by the circadian clock at key times during the day. Once triggered, the whole cycle (i.e. onset, peak and offset) of locomotor activity occurring both at dawn and dusk can proceed autonomously. However, the occurrence of a lights-off signal (typically at dusk) before the autonomous cessation of locomotor activity, leads to a light-driven termination of such activity. In addition, so1 (eye-less) mutant flies show the presence of a single evening locomotor activity peak during the whole circadian day, suggesting that in wild type flies the morning and evening activity peaks may be under separate control.

Fixed text speaker verification method and apparatus

Speaker verification is performed by computing principal components of a fixed text statement comprising a speaker identification code and a two-word phrase, and principal spectral components of a random word phrase. A multi-phrase strategy is utilized in access control to allow successive verification attempts in a single session, if the speaker fails initial attempts. Based upon a verification attempt, the system produces a verification score which is compared with a threshold value. On successive attempts, the criterion for acceptance is changed, and one of a number of criteria must be satisfied for acceptance in subsequent attempts. A speaker normalization function can also be invoked to modify the verification score of persons enrolled with the system who inherently produce scores which result in denial of access. Accuracy of the verification system is enhanced by updating the reference template which then more accurately symbolizes the person's speech signature.

Latitude variation of the spectral components of auroral zone Pi2

Evidence is presented from spectral analysis of Pi2 pulsations detected during a substorm by the University of Alberta meridian chain of magnetometers to support the conclusion that at auroral latitudes there is no apparent correlation between the principal spectral components of Pi2 pulsations and the latitude of the observations. From these data we infer that the Pi2 magnetic variations observed at the Earth's surface are not generated by simple MHD eigenoscillations of magnetospheric field. As well, the data show clear contributions to the Pi2 pulsation spectrum by ionospheric currents. These observations lead to the suggestion that Pi2 pulsation spectra are produced by the sudden changes in magnetospheric and ionospheric current systems which take place at the beginning of a substorm.

Digital single-sideband mixer

A single-sideband (SSB) frequency converter using only exclusive-or logic gates and no reactive or frequency-selective analog circuit elements takes square-wave inputs at two arbitrary frequencies f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> and f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and generates an output waveform whose principal spectral component is at either f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> +f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> or f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> -f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , selectably. A pair of outputs is generated in phase quadrature.

Pressure variations produced at the ocean bottom by hurricanes

Low-frequency pressure variations (0.1 to 3 hz) associated with the near passage of six hurricanes have been detected by a deep (5.7 km) ocean bottom hydrophone (OBH) located approximately 260 km northeast of Antigua, British West Indies. Recordings made during one hurricane, Arlene, that passed almost directly over the OBH site in August 1963 have been analyzed in detail. Two principal pressure spectral components are observed: (1) normal microseisms with prominent spectral peaks at periods of 2.8, 4.6, and 10 sec for Arlene, and (2) a shorter-period component with periods between 0.5 and 1.0 sec but usually at 0.9 sec. Maximum microseisms at the OBH occur many hours after peak hurricane winds have passed the point of closest approach to the hydrophone; hence, generation does not take place directly beneath the storm. The onset of normal microseisms from Arlene occurs at about the same time at Guadeloupe and the OBH, and this closely parallels increased regional ocean wave activity. The predominant periods for wind waves and swell from hurricane Arlene are approximately twice the periods of the 2.8- and 4.6-sec microseismic spectral peaks respectively, suggesting that the microseisms are produced by the interaction of ocean waves as described by Longuet-Higgins. The interaction does not take place within the storm itself. The microseismic spectral peak at a period of 10 sec may be produced by the direct action of the 10-sec swell on local shorelines. Maximum amplitudes for the high-frequency pressure component coincide with the time of a hurricane’s closest approach to the OBH. Thus, it is concluded that this signal is produced directly beneath a hurricane and may serve as a means of tracking its motion.

Electronic excitation of diamond by energetic charged particles

The mean energy, ϵ α., absorbed from α-particles whose energy was varied between 1 and 5.3 MeV in the creation of a free electron-hole pair has been measured for a large number of specimens of natural diamond, using the conduction counting technique. The limiting minimum value found for ϵα(24.5 ± 1 eV) is compared with the previously reported value obtained using β-particle excitation (ϵ β = 18.5 ± 1.5 eV). The observed difference between ϵ α and ϵ β is explained quantitatively in terms of the large ratio between the α and β-particle scintillation efficiencies ( S α/ S β ≑ 50 : 1). The method of measurement of S α. and S β is described. The mechanism of the electronic excitation process is discussed in terms of a plasma resonance of the valence electrons (plasmon creation). The value of ϵ β is interpreted in terms of the decay of the plasmons into the excitation of secondary electrons and the emission of optical phonons. Finally the origin of the large value of s α/ s β is shown, from an analysis of the effect of an externally applied electric field upon the values of s α and s β. to be connected with the magnitude of the self-field produced in the excitation channel (track of the primary particle). The principal spectral component of the scintillation emission (“blue band”) has been previously identified with the extrinsic recombination of excitons, and the effects produced by an electric field on the particle-induced luminescence are discussed in terms of this hypothesis.