Baryon bound state in two-dimensional SU(N) gauge theory

The bound-state baryon problem with N quarks in an SU(N) gauge model of strong interactions is investigated in one-space and one-time dimensions. A study of planar diagrams yields color singlet “baryon” states of quarks that have infrared divergence-free mass spectra. The resulting integral equation turns out to be identical to the one obtained in a particular string model.     

Secondary ion mass spectra of alkali halides

Mass spectra of positive and negative secondary ions from various alkali halides have been measured in the Manitoba time-of-flight mass spectrometer. The ions were produced by Cs⁺ and K⁺ bombardment at primary ion energies of 3 to 19 keV for the positive spectra, and 11 to 28 keV for the negative spectra. The ions measured were those emitted within a time interval ～ 20 ns after the primary ion impact. The secondary ion yields are strongly dependent on the sample composition and treatment; prior irradiation may change the yield by an order of magnitude or more. The secondary ion yields also depend strongly on the energy loss of the primary ion, but the ratio of yields of different cluster ions from a given target is almost independent of this parameter. The results appear to be consistent with models in which the clusters are ejected directly from the target, but do not determine whether or not they possess the original surface structure. The results may also be described by a recombination model if the recombination is essentially complete.     

Renormalization Group Recursion Formulas and Flows of 2D O(N) Spin Models

Renormalization group recursion formulas for classical O(N) spin models in two dimensions are obtained. The main part of the recursion formulas is solved and yields the flows which are very close to those of the hierarchical model approximations of Dyson–Wilson type. Spontaneous mass generations also take place under our approximation.     

Tiny neutrino mass from SUSY and lepton number breaking sector

We suggest a new setup where SUSY breaking spurion F-term possesses lepton number. This setup not only modifies sparticle mass spectra but also realizes several new models, where neutrino mass is naturally induced through radiative corrections. We here suggest two new models; the first one is (i): pseudo-Dirac/Schizophrenic neutrino model, and the second one is (ii): pure Majorana neutrino model. We will also show this setup can naturally apply to the supersymmetric Zee-Babu model.     

Gravitational actions in two dimensions and the Mabuchi functional

The Mabuchi energy is an interesting geometric functional on the space of Kähler metrics that plays a crucial rôle in the study of the geometry of Kähler manifolds. We show that this functional, as well as other related geometric actions, contribute to the effective gravitational action when a massive scalar field is coupled to gravity in two dimensions in a small mass expansion. This yields new theories of two-dimensional quantum gravity generalizing the standard Liouville models.     

Direct ToF-SIMS analysis of organic halides and amines on TLC plates

It has been reported that: “direct analysis of thin layer chromatography (TLC) plates with secondary ion mass spectrometry (SIMS) yields no satisfactory results” (J. Chromatogr. A 1084 (2005) 113-118). While this statement appears to be true in general, we have identified two important classes of compounds, organic halides and amines, that appear to yield to such direct analyses. For example, five organic halides with diverse structures were eluted on normal phase TLC plates. In all cases the halide signals in the negative ion time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra were notably stronger than the background signals. Similarly, a series of five organic amines with diverse structures were directly analyzed by positive ion ToF-SIMS. In all but one of the spectra characteristic, and sometimes even quasi-molecular ions, were observed. Most likely, the good halide ion yields are largely a function of the electronegativity of the halogens. We also propose that direct analysis of amines on normal phase silica gel is facilitated by the acidity, i.e., proton donation, of surface silanol groups.     

Accelerating universe from an evolving Λ in higher dimension

We find exact solutions in 5D inhomogeneous matter dominated model with a varying cosmological constant. Adjusting arbitrary constants of integration one can also achieve acceleration in our model. Aside from an initial singularity our spacetime is regular everywhere including the centre of the inhomogeneous distribution. We also study the analogous homogeneous universe in (4 + d) dimensions. Here an initially decelerating model is found to give late acceleration in conformity with the current observational demands. We also find that both anisotropy and number of dimensions have a role to play in determining the time of flip, in fact the flip is delayed in multidimensional models. Some astrophysical parameters like the age, luminosity distance, etc., are also calculated and the influence of extra dimensions is briefly discussed. Interestingly our model yields a larger age of the universe compared to many other quintessential models.     

Results of radius scaling experiments and analysis of neon K-shellradiation data from an inductively driven Z-pinch

The K-shell radiated energy (yield) from neon Z-pinch implosions with annular, gas-puff nozzle radii of 1, 1.75, and 2.5 cm was measured for implosion times from 50 to 300 ns while systematically keeping the implosion kinetic energy nearly constant. The implosions were driven by the Hawk inductive-storage generator at the 0.65-MA level. Initial neutral-neon density distributions from the nozzles were determined with laser interferometry. Measured yields are compared with predictions from zero-dimensional (0-D) scaling models of ideal. One-dimensional (1-D) pinch behavior to both benchmark the scaling models, and to determine their utility for predicting K-shell yields for argon implosions of 200 to >300 ns driven by corresponding currents of 4 to 9 MA, such as envisioned for the DECADE QUAD. For all three nozzles, the 0-D models correctly predict the Z-pinch mass for maximum yield. For the 1and 1.75-cm radius nozzles, the scaling models accurately match the measured yields if the ratio of initial to final radius (compression ratio) is assumed to be 8:1. For the 2.5-cm radius nozzle, the measured yields are only one-third of the predictions. Analysis of K-shell spectral measurements suggest that as much as 70% (50%) of the imploded mass is radiating in the K-shell for the 1-cm (1.75-cm) radius nozzle. That fraction is only 10% for the 2.5-cm radius nozzle. The 0-D scaling models are useful for predicting 1-D-like K-shell radiation yields (better than a factor-of-two accuracy) when a nominal (≈10:1) compression ratio is assumed. However, the compression ratio assumed in the models is only an “effective” quantity, so that further interpretations based on the 0-D analysis require additional justification. The lower-than-predicted yield for the 2.5-cm radius nozzle is associated with larger radius and not with longer implosion time, and is probably a result of two-dimensional effects     

Strangeness enhancement at midrapidity in Pb–Pb collisions at 158 A GeV/c: A comparison with VENUS and RQMD models

Recently the WA97 Collaboration has measured , , , and negative particle yields and transverse mass spectra at central rapidity in Pb–Pb and p–Pb collisions at 158 A GeV/c. These results are compared with the predictions of two of the most widely used event generators for heavy-ion collisions: VENUS 4.12 and RQMD 2.3. Both models predict that enhancements increase with the strangeness content of the particle. They fail, however, to reproduce completely the measured values of yields at central rapidity. In particular, for multistrange particles, VENUS fails to reproduce both the p–Pb and the Pb–Pb data, while RQMD works for p–Pb collisions but seems to be unable to reproduce the data in Pb–Pb collisions. Moreover, the predicted behavior for strangeness production as a function of the centrality of the collision appears to be different from the observed behavior. Received: 29 April 1999 / Published online: 14 October 1999     

A new program based on stochastic Liouville equation for the analysis of superhyperfine interaction in CW-ESR spectroscopy

In the slow-motion region, ESR spectra cannot be expressed as a sum of simple Lorentzian lines. Studies of Freed and co-workers, on nitroxides in liquids gained information on the microscopic models of rotational dynamics, relying much on computer programs for simulation of ESR spectra based on the stochastic Liouville equation (SLE). However, application of Freed's method to copper system of biological interest has been for a long time precluded by lack of a full program able to simulate ESR spectra containing more than one hyperfine interaction. Direct extension of the Freed's approach in order to include superhyperfine interaction is not difficult from a theoretical point of view but the resulting algorithm is problematical because it leads to substantial increase in the dimensions of the matrix related to the spin-hamiltonian operator. In this paper preliminary results of a new program, written in C, which includes the superhyperfine interactions are presented. This preliminary version of the program does not take into account a restoring potential, so it can be used only in isotropic diffusion conditions. A comparison with an approximate method previously developed in our laboratory, based on a post-convolution approach, is discussed.     

Energy dependence of peripheral reactions induced by heavy ions

Collisions of ¹⁶O ions on targets of ⁹⁴Zr, ¹⁹⁷Au, ²⁰⁸Pb, and ²³²Th are investigated at incident energies of 140 and 315 MeV and compared to published data on peripheral collisions at 33.6 GeV. At 140 MeV, the isotope-production cross sections resemble the ground-state Q-value systematics characteristic of a partially-equilibrated, di-nuclear system formed in deeply-inelastic scattering. The yields are independent of shell and pairing effects in the target and residual nuclie. These Q-value systematics fail at 315 MeV, where the relative element yields are similar to those at 33.6 GeV. A theory of projectile fragmentation accounts for the shapes of the inclusive energy spectra as well as for the isotope yields at both energies. The relative cross sections are target independent (i.e., factorize) for the data at 315 MeV incident energy, but limiting fragmentation (i.e. isotope yields independent of energy) applies only at higher energies. The differential cross sections peal at the grazing angle or decrease exponentially, depending on the incident energy and the mass of the ejectile; the distributions are described by classical trajectories and diffraction models for which the reaction time is estimated to be typical of direct reactions. The kinetic energies of the reaction products depend primarily on their charge and only slightly on their mass number. For the 315 MeV results, the velocities of the reaction products at the maximum of the spectrum and the grazing angle are slightly less than the beam velocity and decrease rapidly for larger scattering angles. The results are interpreted with simple fraction and fragmentation models, and are compared to observations at 33.6 GeV.     

High-Resolution Four-Dimensional HMQC-NOESY-HSQC Spectroscopy

Practical optimization of the 4D [(1)H, (13)C, (13)C, (1)H] HMQC-NOESY-HSQC experiment in terms of distribution of resolution over the indirect dimensions is analyzed in detail. Recommendations for an optimal experiment are based on computer simulations assessing the effective resolution of the experiment, defined as the percentage of all possible NOE cross peaks that can be assigned unambiguously on the basis of the spectral data alone. Using actual (13)C-(1)H spectra of an 18-kDa chaperone protein, the analysis shows that experiments with the best effective resolution are also among the most sensitive ones. When combined with an efficient aliasing scheme that reduces indirect spectral space 124-fold, a 4D experiment that yields unambiguous assignments for 41% of all possible NOE cross peaks can be recorded in 28 h. A high-resolution experiment, which can be recorded in 8 days, yields 61% unambiguous assignments and can be analyzed more easily using standard NMR display software. The predictions are verified with experimental 4D spectra from which 1850 NOEs (914 long-range) were extracted for the 18-kDa chaperone protein.     

Nuclear-matter modification of decay widths in the phi-->e+e- and phi-->K+K- channels

The invariant mass spectra of phi-->K+K- are measured in 12 GeV p+A reactions in order to search for the in-medium modification of phi mesons. The observed K+K- spectra are well reproduced by the relativistic Breit-Wigner function with a combinatorial background shape in three betagamma regions between 1.0 and 3.5. The nuclear mass number dependence of the yields of the K+K- decay channel is compared to the simultaneously measured e+e- decay channel for carbon and copper targets. We parameterize the production yields as sigma(A)=sigma0Aalpha and obtain alphaphi-->K+K- -alphaphi-->e+e- to be 0.14+/-0.12. Limits are obtained for the partial decay widths of the phi mesons in nuclear matter.     

Multistrange baryon production in Au-Au collisions at sqrt[s(NN)]=130 GeV

The transverse mass spectra and midrapidity yields for Xis and Omegas are presented. For the 10% most central collisions, the (-)Xi(+)/h(-) ratio increases from the Super Proton Synchrotron to the Relativistic Heavy Ion Collider energies while the Xi(-)/h(-) stays approximately constant. A hydrodynamically inspired model fit to the Xi spectra, which assumes a thermalized source, seems to indicate that these multistrange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to pi, K, p, and Lambdas.     

光谱信息降维及判别模型建立用于识别湿地植物物种

研究分析了北京地区常见湿地植物的高光谱数据特征。主要采用马氏距离法和主成分分析法对光谱进行降维,并对光谱特征进行分析和提取;利用提取的光谱信息构建判别模型对湿地植物进行判别,并对模型精度进行比较评价,最后获得最佳判别模型。研究结果显示:(1)马氏距离法和主成分分析法都能对光谱进行有效降维,(2)利用从光谱中提取的特征参数建立的判别模型,得到物种识别的精度都高于90%。可见,湿地植物高光谱数据信息的变换和利用能促进对湿地植物光谱特征的认识和提取,而建立模型进行植物判别可以指导未来遥感领域的湿地制图和监测。     

Localization of excitons in weakly disordered semiconductor structures: A model study

Localization of the center‐of‐mass (com) motion of an exciton in a disordered semiconductor structure is studied theoretically by focusing on nonlinear optical spectroscopy. A one‐dimensional tight‐binding model with diagonal disorder is applied and the Coulomb interaction is treated consistently. In the ordered situation the center‐of‐mass momentum (K) selection rule leads to only the lowest transition for K = 0. The break down of the com‐K‐selection rule produces the well known asymmetric excitonic lines of disordered semiconductors. The coupling between the lowest dominant transition to this modified com‐continuum yields Fano‐like features in the nonlinear spectra.     

Fitting of deuterium quadrupole echo spectra with multiple motional models

Dynamic information is generally extracted from deuterium quadrupole echo spectra by matching a spectrum calculated for a particular motional model to the experimental spectrum. In this work, a set of computer programs has been written to facilitate fitting of calculated spectra to experimental spectra that represent from one to five motional models. The fitting program requires pre-calculated libraries of spectra for the models of interest, and accomplishes the fitting either by a systematic method or by simulated annealing. The systematic method is convenient for fitting with one or two motional models, but the simulated annealing method is faster for two or more models, if the libraries are made up of hundreds of spectra. The parameter Q, with the standard deviation of the spectral points estimated as the standard deviation of the baseline noise, provides a stringent measure of goodness of fit. Acceptable fits of experimental data as judged by this criterion have not been found, even in the case of ring flip motion in phenylalanine-d(5) in which the fit may be judged acceptable by eye. An example of fitting with isotropic and methyl rotation motional models of alanine-d(3), which have distinct spectral patterns, shows that it is possible to obtain reasonably accurate estimates of the relative amounts of deuterium representing the different models, even from poorly fitted spectra.     

Quantum fluctuations, temperature, and detuning effects in solid-light systems

The superfluid to Mott insulator transition in cavity polariton arrays is analyzed using the variational cluster approach, taking into account quantum fluctuations exactly on finite length scales. Phase diagrams in one and two dimensions exhibit important non-mean-field features. Single-particle excitation spectra in the Mott phase are dominated by particle and hole bands separated by a Mott gap. In contrast to Bose-Hubbard models, detuning allows for changing the nature of the bosonic particles from quasilocalized excitons to polaritons to weakly interacting photons. The Mott state with density one exists up to temperatures T/g > or = 0.03, implying experimentally accessible temperatures for realistic cavity couplings g.     

Multiphoton ionization studies of amines with UV-VIS lasers

Three and four photon ionization studies at 355 and 532 nm are presented for the isomeric propylamines and n-pentylamine. Ionic fragmentation patterns and ion yields are presented as a function of laser wavelength and fluence. These time-of-flight (TOF) mass spectra are compared with both electron impact data and the TOF mass spectra of the previously reported butylamines. A brief discussion of the dynamics of the decomposition process is presented in light of the butylamine results and competitive ionic fragmentation pathways.