Multidimensional Spectrum Research Articles

Does ℏ Play a Role in Multidimensional Spectroscopy? Reduced Hierarchy Equations of Motion Approach to Molecular Vibrations

To investigate the role of quantum effects in vibrational spectroscopies, we have carried out numerically exact calculations of linear and nonlinear response functions for an anharmonic potential system nonlinearly coupled to a harmonic oscillator bath. Although one cannot carry out the quantum calculations of the response functions with full molecular dynamics (MD) simulations for a realistic system which consists of many molecules, it is possible to grasp the essence of the quantum effects on the vibrational spectra by employing a model Hamiltonian that describes an intra- or intermolecular vibrational motion in a condensed phase. The present model fully includes vibrational relaxation, while the stochastic model often used to simulate infrared spectra does not. We have employed the reduced quantum hierarchy equations of motion approach in the Wigner space representation to deal with nonperturbative, non-Markovian, and nonsecular system-bath interactions. Taking the classical limit of the hierarchy equations of motion, we have obtained the classical equations of motion that describe the classical dynamics under the same physical conditions as in the quantum case. By comparing the classical and quantum mechanically calculated linear and multidimensional spectra, we found that the profiles of spectra for a fast modulation case were similar, but different for a slow modulation case. In both the classical and quantum cases, we identified the resonant oscillation peak in the spectra, but the quantum peak shifted to the red compared with the classical one if the potential is anharmonic. The prominent quantum effect is the 1-2 transition peak, which appears only in the quantum mechanically calculated spectra as a result of anharmonicity in the potential or nonlinearity of the system-bath coupling. While the contribution of the 1-2 transition is negligible in the fast modulation case, it becomes important in the slow modulation case as long as the amplitude of the frequency fluctuation is small. Thus, we observed a distinct difference between the classical and quantum mechanically calculated multidimensional spectra in the slow modulation case where spectral diffusion plays a role. This fact indicates that one may not reproduce the experimentally obtained multidimensional spectrum for high-frequency vibrational modes based on classical molecular dynamics simulations if the modulation that arises from surrounding molecules is weak and slow. A practical way to overcome the difference between the classical and quantum simulations was discussed.

Using NMR Metabolomics to Investigate Tricarboxylic Acid Cycle-dependent Signal Transduction in Staphylococcus epidermidis

Staphylococcus epidermidis is a skin-resident bacterium and a major cause of biomaterial-associated infections. The transition from residing on the skin to residing on an implanted biomaterial is accompanied by regulatory changes that facilitate bacterial survival in the new environment. These regulatory changes are dependent upon the ability of bacteria to "sense" environmental changes. In S. epidermidis, disparate environmental signals can affect synthesis of the biofilm matrix polysaccharide intercellular adhesin (PIA). Previously, we demonstrated that PIA biosynthesis is regulated by tricarboxylic acid (TCA) cycle activity. The observations that very different environmental signals result in a common phenotype (i.e. increased PIA synthesis) and that TCA cycle activity regulates PIA biosynthesis led us to hypothesize that S. epidermidis is "sensing" disparate environmental signals through the modulation of TCA cycle activity. In this study, we used NMR metabolomics to demonstrate that divergent environmental signals are transduced into common metabolomic changes that are "sensed" by metabolite-responsive regulators, such as CcpA, to affect PIA biosynthesis. These data clarify one mechanism by which very different environmental signals cause common phenotypic changes. In addition, due to the frequency of the TCA cycle in diverse genera of bacteria and the intrinsic properties of TCA cycle enzymes, it is likely the TCA cycle acts as a signal transduction pathway in many bacteria.

A DSS for Real Estate Location Choice

The evaluation of real estate assets is currently one of the main issues addressed by territorial marketing strategies with a view to developing competitive cities. Given the complexity of the real estate market, it's hard to identify a priori the factors that constitute a city's competitive capacity to attract investments to this market. In this paper we design an integrated complex evaluation model able to map out and encapsulate the multidimensional spectrum of factors that shape the attractiveness each investment destination. The methodological approach is then illustrated through application of the model to a real-world case of investment choice in the residential sector of the city of Naples.

Filter diagonalization using a “sensitivity-enhanced basis”: Improved performance for noisy NMR spectra

The Filter Diagonalization Method (FDM) has been used to process NMR data in liquids and can be advantageous when the spectrum is sparse enough, the lines are sharp and Lorentzian, raw sensitivity is adequate, and the measured time-domain data is short, so that the Fourier Transform spectrum exhibits distorted line shapes. Noise can adversely impact resolution and/or frequency accuracy in FDM spectral estimates. Paradoxically, more complete data can lead to worse FDM spectra if there is appreciable noise. However, by modifying the numerical method, the FDM noise performance improves significantly, without apparently losing any of the existing advantages. The two key modifications are to adjust the FDM basis functions so that matrix elements computed from them have less noise contribution on average, and to regularize each dimension of a multidimensional spectrum independently. The modifications can be recommended for general-purpose use in the case of somewhat noisy, incomplete data.

A versatile ultrastable platform for optical multidimensional Fourier-transform spectroscopy

The JILA multidimensional optical nonlinear spectrometer (JILA-MONSTR) is a robust, ultrastable platform consisting of nested and folded Michelson interferometers that can be actively phase stabilized. This platform generates a square of identical laser pulses that can be adjusted to have arbitrary time delay between them while maintaining phase stability. The JILA-MONSTR provides output pulses for nonlinear excitation of materials and phase-stabilized reference pulses for heterodyne detection of the induced signal. This arrangement is ideal for performing coherent optical experiments, such as multidimensional Fourier-transform spectroscopy, which records the phase of the nonlinear signal as a function of the time delay between several of the excitation pulses. The resulting multidimensional spectrum is obtained from a Fourier transform. This spectrum can resolve, separate, and isolate coherent contributions to the light-matter interactions associated with electronic excitation at optical frequencies. To show the versatility of the JILA-MONSTR, several demonstrations of two-dimensional Fourier-transform spectroscopy are presented, including an example of a phase-cycling scheme that reduces noise. Also shown is a spectrum that accesses two-quantum coherences, where all excitation pulses require phase locking for detection of the signal.

The Concept of Information Transparency: A Spectrum in Four-Dimensional Space

The concept of in organizations has been commonly and frequently used as an almost all-encompassing concept, without sufficient clarification as to what this compound term means or what it may be comprised of. The premise underlying the issue of is that organizations and managers tend to reveal as little as they can whereas stakeholders demand higher levels of transparency. This incompatibility of interests, the agency problem, is not sufficiently explored and clarified. Evidently, for example, different stakeholders require different kinds of information, amounts of it or relevant details. Hence, information transparency is a concept that remains essentially uncontested by its users, leaving it an opaque concept. The question then arises: how could it be unpacked and clarified? We assert that consists of the following dimensions: relevance, accessibility, revelation and quality. That is, we argue that is a multidimensional spectrum consisting of the above dimensions. As such, is a spectrum in a four dimensional space, and we propose an analytical depiction of it. Our purpose is to provide a critical review of the extent to which organizational ought to be revealed and become transparent to stakeholders. A logical analysis of the concept is used, side by side with anecdotal and case evidence, to illustrate the complexity associated with different levels of of organizational in ethical dilemmas.

Principles and Progress in Ultrafast Multidimensional Nuclear Magnetic Resonance

Multidimensional acquisitions play a central role in the progress and applications of nuclear magnetic resonance (NMR) spectroscopy. Such experiments have been collected traditionally as an array of one-dimensional scans, with suitably incremented delay parameters that encode along independent temporal domains the nD spectral distribution being sought. During the past few years, an ultrafast approach to nD NMR has been introduced that is capable of delivering any type of multidimensional spectrum in a single transient. This method operates by departing from the canonical nD NMR scheme and by replacing its temporal encoding with a series of spatial manipulations derived from magnetic resonance imaging. The present survey introduces the main principles of this subsecond approach to spectroscopy, focusing on the applications that have hitherto been demonstrated for single-scan two-dimensional NMR in different areas of chemistry.

Conditional affinity spectra underlying NICA isotherm

The properties of the NICA (non-ideal competitive adsorption) isotherm are examined from the point of view of the underlying conditional affinity spectra (CAS), the distribution of effective affinities seen by a given metal ion at a fixed pH. It is shown that a CAS underlying NICA isotherm exists for all combinations of p- and n i-values including cases with different n i-values for the competing species (protons and metal ions). These distributions shift towards lower affinity values and change their shape as pH decreases. For instance, the conditional distributions can show two peaks within a monomodal NICA isotherm with quite negative minimum skewness, preferably for low enough p-values. Analytical expressions and a full discussion of this behaviour are reported with the aim of providing a complementary understanding of the physical meaning of the NICA parameters. Parameter p mainly influences the correlation between the binding energies of the competing ions. In general, when there is no multidimensional affinity spectrum, low p-values are usually associated with strong affinity sites for the proton tending to be involved in high affinity sites for the metal (i.e. there is correlation in a broad sense). The rate of shift of the average conditional affinity with pH is mainly determined by the proton affinities and the stoichiometric relationship, n M/ n H, which determines the proton/metal ion exchange work.

A multidimensional spectrum approach to post-traumatic stress disorder: comparison between the Structured Clinical Interview for Trauma and Loss Spectrum (SCI-TALS) and the Self-Report instrument (TALS-SR)

Dimensional approaches to psychiatric disorders have shown an increased relevance in the ongoing debate for the forthcoming Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. In line with previously validated instruments for the assessment of different mood, anxiety, eating and psychotic spectra, we tested the validity and reliability of a newly developed Structured Clinical Interview for Trauma and Loss Spectrum (SCI-TALS). The instrument is based on a multidimensional approach to post-traumatic stress spectrum that includes a range of threatening or frightening experiences, as well as a variety of potentially significant losses, to which an individual can be exposed. Furthermore, it explores the spectrum of the peritraumatic reactions and post-traumatic symptoms that may ensue from either type of life events, targeting soft signs and subthreshold conditions, as well as temperamental and personality traits that may constitute risk factors for the development of the disorder. The aim of the present study is to describe the reliability of the self-report version of the SCI-TALS: the TALS-SR. Thirty patients with PTSD and thirty healthy control subjects were assessed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Half of the patients and controls received the TALS-SR first and the SCI-TALS after 15 days; for the other half of the sample, the order of administration was reversed. Agreement between the self-report and the interview formats was substantial. Intraclass correlation coefficients ranged from 0.934 to 0.994, always exceeding the threshold of 0.90. Our findings provide substantial support for the reliability of the TALS-SR questionnaire.

A survey of spectrum sensing algorithms for cognitive radio applications

The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.

Exploring effects of type 2 diabetes on cognitive functioning in older adults.

Type 2 diabetes may be associated with exacerbated aging-related declines in cognitive neuropsychological performance. The authors examined whether such effects are systematic (i.e., broadly distributed across domains or domain-specific) or moderated by age (i.e., varying across age within older adults). The authors assembled recent cross-sectional data from the Victoria Longitudinal Study (VLS) Sample 3 (Wave 1; initial n = 570; initial age = 53-90 years). Using a comprehensive, multidimensional spectrum of cognitive neuropsychological tests, the authors examined performance differences by diabetes status (diabetes group vs. healthy controls) and age (young-old vs. old-old). Our results showed that healthy controls significantly outperformed the diabetes group only on markers of executive functioning and speed. Notably, the diabetes-related effects were robust across the two late-life age groups. Future research examining longitudinal changes is recommended.

Exact Relativistic Kinetic Theory of an Electron-Beam–Plasma System: Hierarchy of the Competing Modes in the System-Parameter Space

The stability analysis of an electron-beam-plasma system is of critical relevance in many areas of physics. Surprisingly, decades of extensive investigation have not yet resulted in a realistic unified picture of the multidimensional unstable spectrum within a fully relativistic and kinetic framework. All attempts made so far in this direction were indeed restricted to simplistic distribution functions and/or did not aim at a complete mapping of the beam-plasma parameter space. The present Letter comprehensively tackles this problem by implementing an exact linear model. Three kinds of modes compete in the linear phase, which can be classified according to the direction of their wave number with respect to the beam. We determine their respective domain of preponderance in a three-dimensional parameter space and support our results with multidimensional particle-in-cell simulations.

Fluctuation-dissipation relationships between multidimensional bispectra and power-density spectra, satisfying the principle of dual symmetry

The principle of dual symmetry is used for the deriving of dual multidimensional fluctuation-dissipation relationships between a multidimensional bispectrum of equilibrium noise and a derivative of multidimensional power-density spectrum with respect to external disturbance (in the form of direct current or voltage).

Motives for Nonsuicidal Self-Injury Among Women With Borderline Personality Disorder

Patients with borderline personality disorder (BPD) are known to use nonsuicidal self-injury (NSSI) as a dysfunctional strategy to regulate intense emotions. The primary purpose of this study was to clarify the motives for NSSI along with their interrelations. We further investigated the variety of emotions preceding NSSI and possible effects of NSSI on these emotions. To this end, a structured self-rating questionnaire on NSSI was administered to 101 female BPD-patients exhibiting NSSI. Most patients reported multiple motives for NSSI. The motives were more likely to compound than to exclude one another. Negative reinforcement was almost always involved in NSSI, whereas positive reinforcement (e.g., "getting a kick") played an additional role among about half of the patients. NSSI was usually preceded by a large variety of negative feelings that were reported to clearly improve with NSSI. In conclusion, therapists should anticipate a multidimensional functional spectrum when exploring motives of NSSI.

Design of a Novel Multi-Dimensional HCOC Multi-code Spread Spectrum System Using Pre-coding Technique for High Speed Data Transmission of DS-CDMA

Recently, Mc (Multi-code) modulation/demodulation (modem) technique has been explored for the high speed data transmission in wireless environment. The conventional Mc modem can generate some side effects such as allocating Walsh codes, which motivates the researchers in [1] to propose a novel Mc modem method with sub-code. But this proposed system should expand the size of sub-code to provide high-rate data transmission, which also affect adversely the performance of the system with high PAPR (Peak to Average Power Ratio). Thus, in this paper, we propose a novel pre-coded Multi-Dimensional HCOC (High Capacity Orthogonal Code) Mc modem technique to reduce the high PAPR, which enables the performance improvement. This proposed system can be easily designed by concatenating HCOC Mc modem with the generic Mc modem. The pre-coding technique that is used in this paper is called CAC (Constant Amplitude Coding) helps the system maintain the constant transmission power and reduce the maximum transmission power.

Tailoring globalisation to national needs and well-being: one size never fits all

This paper argues that political-economic trends referred to under the single heading of globalisation have distinct causes and manifestations in different countries. Institutional variables chosen by governments and their constituents play a dominant role in determining the character of those manifestations, few of which are inevitable. The political Left and Right often base their arguments on the common premise that nations have no choice but to adopt the US model of highly mobile investment capital, market-centred provision of most goods, minimal governmental regulation and minimisation of accounting costs. That countries possess considerable degrees of freedom in establishing rules for international flows of labour, capital and goods is insufficiently appreciated by critics and supporters of trade and labour market liberalisation. Variety in political-economic forms achieves institutional diversification on a global scale, providing a multi-dimensional spectrum of benchmarks that help individual countries measure policy performance and update institutional variables accordingly.

The Plenacoustic Function and Its Sampling

The spatialization of the sound field in a room is studied, in particular the evolution of room impulse responses as a function of their spatial positions. It was observed that the multidimensional spectrum of the solution of the wave equation has an almost bandlimited character. Therefore, sampling and interpolation can easily be applied using signals on an array. The decay of the spectrum is studied on both temporal and spatial frequency axes. The influence of the decay on the performance of the interpolation is analyzed. Based on the support of the spectrum, the number and the spacing between the microphones is determined for the reconstruction of the sound pressure field up to a certain temporal frequency and with a certain reconstruction quality. The optimal sampling pattern for the microphone positions is given for the linear, planar and three-dimensional case. Existing techniques usually make use of room models to recreate the sound field present at some point in the space. The presented technique simply starts from the measurements of the sound pressure field in a finite number of positions and with this information the sound pressure field can be recreated at any spatial position. Finally, simulations and experimental results are presented and compared with the theory

Impulsivity and compulsivity in patients with trichotillomania or skin picking compared with patients with obsessive-compulsive disorder

To compare impulsivity and compulsivity, we performed a case control study comparing a group of 20 patients with obsessive-compulsive disorder with a group of 20 patients with skin picking and/or trichotillomania (SP/T). The instruments used were Structured Clinical Interview for DSM-IV Axis I Diagnosis, Yale-Brown Obsessive-Compulsive Scale, Schalling Impulsivity Scale, and Hamilton Anxiety and Depression Inventories. A Multidimensional Impulsive-Compulsive Spectrum Assessment Instrument was designed for this particular study. The Yale-Brown Obsessive-Compulsive Scale scores were significantly higher in patients with obsessive-compulsive disorder, compared with patients with SP/T ( F = 90.29; P < .001). The Hamilton Inventories and Schalling Impulsivity Scale revealed no significant intergroup differences. The Multidimensional Impulsive-Compulsive Spectrum Assessment Instrument allowed us to find 6 statistically significant differences between groups: the ability or inability to delay an impulse, quick response or action planning, feelings of pleasure or guilt during or after an act, ritualization, and whether the patient believes he/she has losses or benefits if prevented from acting. In conclusion, SP/T should deserve further attention about their classification in future versions of diagnostic manuals because, as in International Classification of Diseases, Tenth Revision, the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition includes these disorders in the same chapter as pathological gambling, kleptomania, pyromania and others. Despite their resemblance to compulsions, their classification under the Obsessive-Compulsive Spectrum needs particular phenomenological and neurobiologic investigation.

Three-dimensional-IR spectroscopy: Beyond the two-point frequency fluctuation correlation function

Three-dimensional-IR spectroscopy is proposed as a new spectroscopic technique that is sensitive to three-point frequency fluctuation correlation functions. This will be important when the statistics of the underlying stochastic process is non-Gaussian, and hence when the system does not follow the linear response hypothesis. Furthermore, a very general classification of nonlinear spectroscopy in terms of higher order frequency fluctuation correlation functions is introduced, according to which certain moments of a multidimensional spectrum are related to certain frequency fluctuation correlation functions. The classification is rigorous in the so-called inhomogeneous limit, but remains valid approximately also when motional narrowing becomes important. The work also puts a recent paper [J. Bredenbeck et al., Phys. Rev. Lett. 95, 083201 (2005)] onto solid theoretical grounds, where we have shown for the first time that fifth-order spectroscopy--in this case transient two-dimensional spectroscopy--is indeed sensitive to the three-point frequency fluctuation correlation function.

Deterministic and statistical methods for reconstructing multidimensional NMR spectra

Reconstruction of an image from a set of projections is a well-established science, successfully exploited in X-ray tomography and magnetic resonance imaging. This principle has been adapted to generate multidimensional NMR spectra, with the key difference that, instead of continuous density functions, high-resolution NMR spectra comprise discrete features, relatively sparsely distributed in space. For this reason, a reliable reconstruction can be made from a small number of projections. This speeds the measurements by orders of magnitude compared to the traditional methodology, which explores all evolution space on a Cartesian grid, one step at a time. Speed is of crucial importance for structural investigations of biomolecules such as proteins and for the investigation of time-dependent phenomena. Whereas the recording of a suitable set of projections is a straightforward process, the reconstruction stage can be more problematic. Several practical reconstruction schemes are explored. The deterministic methods-additive back-projection and the lowest-value algorithm-derive the multidimensional spectrum directly from the experimental projections. The statistical search methods include iterative least-squares fitting, maximum entropy, and model-fitting schemes based on Bayesian analysis, particularly the reversible-jump Markov chain Monte Carlo procedure. These competing reconstruction schemes are tested on a set of six projections derived from the three-dimensional 700-MHz HNCO spectrum of a 187-residue protein (HasA) and compared in terms of reliability, absence of artifacts, sensitivity to noise, and speed of computation.