Crystal structures of a pair of diastereomeric 3-(N,N-dimethylammonium)-1,1-diphenyl-1-butanol hydrogen tartrates

The crystal structures of a pair of diastereomeric salts of (2R, 3R)- (+)-tartaric acid and (–)-and (+)-3-N,N-dimethylamino-1,1-diphenyl-1-butanol have been determined. Crystal data: 1: (R)-(–)-C₁₈H₂₄NO⁺, , C2, a = 38.198(7), b = 5.841(2), c = 9.993(2)Å, = 102.63(1)°, V = 2175.6(1) ų, Z = 4, D _calc = 1.281 g cm^–3. 2: (S)-(+)-C₁₈H₂₄NO⁺, P2₁2₁2₁, a = 6.037(2), b = 8.5947(8), c = 39.74(1)Å, V = 2062.0(9) ų, Z = 4, D _calc = 1.351 g cm^–3. The conformations of the 3-(N,N-dimethylammonium)-1,1-diphenyl-1-butanol cations in the two salts are almost mirror images of each other, but the cation in 2 has an intramolecular hydrogen bond. The hydrogen tartrate ions adopt an extended conformation. The hydrogen bonding networks in the two salts are very different. The absolute configuration of (–)-3-(N,N-dimethylamino)-1,1-diphenyl-1-butanol (1) was established as R.     

Recoupled Polarization Transfer Heteronuclear H–C Multiple-Quantum Correlation in Solids under Ultra-fast MAS

A new approach for high-resolution solid-state heteronuclear multiple-quantum MAS NMR spectroscopy of dipolar-coupled spin- nuclei is introduced. The method is a heteronuclear chemical shift correlation technique of abundant spins, like ¹H with rare spins, like ¹³C in natural abundance. High resolution is provided by ultra-fast MAS and high magnetic fields, high sensitivity being ensured by a direct polarization transfer from the abundant protons to ¹³C. In a rotor-synchronized variant, the method can be used to probe heteronuclear through-space proximities, while the heteronuclear dipolar coupling constant can quantitatively be determined by measuring multiple-quantum spinning-sideband patterns. By means of recoupling, even weak heteronuclear dipolar interactions are accessible. The capabilities of the technique are demonstrated by measurements on crystalline -tyrosine hydrochloride salt.     

Influence of the surface pretilt angle on spatially periodic deformations in nematic layers

The deformations induced by electric field in twisted or untwisted flexoelectric nematic layers can be homogeneous (i.e. one-dimensional) or spatially periodic (i.e. two-dimensional). The periodic deformations are undesirable from an applicative point of view since they destroy the homogeneous appearance of the area of an excited pixel of a display. They are particularly favoured when the nematic material possesses flexoelectric properties. In order to check whether the unwanted periodic deformations can be eliminated by means of suitable surface pretilt angle, the small deformations arising just above the corresponding threshold voltage were investigated numerically. The nematic materials exhibiting both weak and strong flexoelectricity were taken into account. The surface pretilt angles ranging from 0° to 30° were adopted. It was shown that the periodic patterns, arising in the case of planar surface alignment, disappear if sufficiently large surface pretilt angle is applied.     

Identification of stochastic operators

Based on the here developed functional analytic machinery we extend the theory of operator sampling and identification to apply to operators with stochastic spreading functions. We prove that identification with a delta train signal is possible for a large class of stochastic operators that have the property that the autocorrelation of the spreading function is supported on a set of 4D volume less than one and this support set does not have a defective structure. In fact, unlike in the case of deterministic operator identification, the geometry of the support set has a significant impact on the identifiability of the considered operator class. Also, we prove that, analogous to the deterministic case, the restriction of the 4D volume of a support set to be less or equal to one is necessary for identifiability of a stochastic operator class.     

New fourth-order partial differential equations for filtering in electronic speckle pattern interferometry fringes

Partial differential equations (PDEs) based methods have been demonstrated to be a powerful tool for filtering in electronic speckle pattern interferometry fringe or wrapped phase patterns. In this paper, we derive the new fourth-order partial differential equations (NFOPDE) with a better performance for filtering in electronic speckle pattern interferometry fringe patterns based on the variational methods. We test the proposed models on two computer-simulated speckle fringe patterns and an experimentally obtained fringe pattern, respectively, and compare our models with the widely used, well-known the second-order selective degenerate diffusion PDE model (SOSDPDE) and the published fourth-order PDE model (PFOPDE). The proposed NFOPDE can overcome the shortages that both the SOSDPDE and PFOPDE encounter. In all cases, our NFOPDE outperforms SOSDPDE and PFOPDE.     

Study of deposition patterns of plating layers in SiC/Cu composites by electro-brush plating

SiC reinforced copper composite coatings were prepared by electro-brush plating with micron-size silicon carbide (SiC) ranging from 1 to 5 μm on pure copper sheet in this paper. The micro-structural characterizations of SiC/Cu composite coatings were performed by optical microscope and Scanning Electron Microscope (SEM) coupled with spectrometer, to study co-deposition mechanism of SiC/Cu. It was found that there were three different patterns of SiC deposition in plating layers during electro-brush plating process, i.e. the particles could deposit inside copper grains, in grain boundaries, or in holes of the surface. To investigate deposition mechanism of each pattern, size of SiC and copper grains was compared. By comparison of size of copper grains and hard particles, SiC were either wrapped in copper grains or deposited in grain boundaries. Moreover, electro-brush plating layers at different brush velocities and current densities were obtained respectively, to analyze the microstructure evolution of the composite coatings. The hardness of plating layers was measured. The results indicated at the current density of 3 A/dm², the SiC/Cu coating was compact with SiC content at a high level and the hardness reached a maximum.     

MFM studies of magnetic domain patterns in bulk barium ferrite (BaFe12O19) single crystals

Magnetic domain patterns in bulk barium ferrite (BaFe₁₂O₁₉; BaM) single crystals on the basal plane and the prism plane were measured and studied by magnetic force microscopy (MFM). The surface domain pattern is in the form of flowers or star on the basal plane and long elongated spikes or stripe domains on the prism plane. The change in domain structure with applied field (H_app) and the thickness (T) dependence on domain width (δ) was observed. The domain width decreased from 32 to 9 μm for the crystals of 800-100 μm thicknesses, respectively.     

Single-machine scheduling with positional due indices and positional deadlines

In this paper, we study single-machine scheduling problems with due dates, positional due indices, deadlines and positional deadlines. The scheduling criteria studied in this paper include the number of position-violated tasks, the weighted number of position-violated tasks, and the maximum positional lateness of tasks, by also combining with other traditional scheduling criteria. For each problem, we either provide a polynomial-time algorithm or present an NP-hardness proof.     

Analysis of the traditional medicine YiGan San by the fragmentation patterns of cadambine indole alkaloids using HPLC coupled with high‐resolution MS

YiGan San (YGS) has long been used in traditional Japanese and Chinese folk medicine and serves as a potent and novel therapeutic agent to treat Alzheimer's disease. In the present study, a rapid and sensitive method based on HPLC coupled with diode‐array detection and quadrupole TOF MS (Q‐TOF‐MS) was designed to reveal the chemical constituents of YGS. Thirty‐six compounds were identified and assigned in YGS, including 14 alkaloids, nine γ‐lactones, six flavonoids, three triterpenoid saponinares, two small molecular organic acids, and two other types of compounds. In addition, the accurate fragment weight and MS/MS fragmentation reactions of a subtype indole alkaloid in Uncariae ramulus cum uncis were summarized for the first time to realize rapid identification without reference substances. For the first time, 11 major constituents were comprehensively quantified with a HPLC coupled with triple‐quadrupole MS method. A three‐section switch was used to realize such multicomponent identification. The contents of saikosaponin B₂ and isoliquiritin, which produce anti‐inflammatory and antidepressant‐like effects, were extremely different, up to 700 times, in two sources of YGS. The developed qualitative and quantitative method was proved to be precise, accurate, and reproducible.