Revisions of P-1 Space Groups to Higher Symmetry Space Groups

The space groups of 244 crystal structures originally reported as P-1 are revised to space groups of higher symmetry. The largest number involves revisions to P2/c and C2/c.

A Simple Approach for Synthesis of TAPO-11 Molecular Sieve with Controllable Space Group

A TAPO-11 molecular sieve with the space group lcm2 was synthesized successfully. The samples with different space group were controlled simply only by adjusting the crystallization temperature （CT） in the hydrothermal system. In the system of gel with a molar composition of 0.7R- xTiO2： P2O5： Al2O3： 30H2O, where x is 0.01-0.10 and the R is a mixture of di-n-propylamine and diisopropylamine as templates. When CT was between 150-160℃, the calcined sample showed the space group of Icm^2, while it showed Pna21 at CT larger than 190℃. The characterizations of UV-Vis and FT-IR confirmed that Ti was incorporated into the AEL framework successfully.

New Investigation on the Space Group of Chevkinite

Chevkinite specimen from a rare-earth mineral deposit in Sichuan, southwest of China have been studied in detail by means of transmission electron microscope (TEM).The selected area electron diffraction (SAED)and convergent beam electron diffraction (CBED) patterns , obtained from different crystal zone axis direction , proved coincidently that the space group of chevkinite is C2/m . Fringe lattice image observation showed the mineral crystal is structurally uniform in microscale , and it is an ideal specimen for electron diffraction analysis . The mineral studied here is similar to the one from Bayan Obo , Inner Mongolia , China , in chemical composition and REE distribution . The chemical formula of the crystal is (Ce , La ,… , Ca) 4 Fe2+ (Fe, Ti, Nb) 2 O8 (Si2O7)2 From our study , we come to the conclusion that the space group of the natural chevkinite is C2/m , instead of P21/a as synthetic one . Up to now , chevkinite compositionally similar to the synthetic one , in which the complete replacements of Ce , La by Nd and Fe by Mg or Co occur , has not been discovered in nature . So we suggest that the name for synthesized chevkinite should be further discussed .

The C-G coefficients for the space group D_6~1h

In this paper, the eigenfunction method established by Chen Jin-quan is used to compute the C-G coefficients in regard to the coupling between symmetry points and lines in the first Brillouin zone of the structure D6h^1, space group. Therewith, the wave vector selection rule and the C-G series, are also given as the middle result of computing the C-G coefficients.

DETERMINATION OF SPACE GROUP OF PrCo_(12)B_6 COMPOUND BY CONVERGENT BEAM ELECTRON DIFFRACTION

The space group of PrCo_(12)B_6,compound has been determined using the convergent beam elec- tron diffraction method.The space group is found to be R3m.

Space Group of Aquaimidazolemaleatozinc, [(H_2O)(C_3H_4N_2)(O_2CCH=CHCO_2Zn)]_n

The space group of [(H2O)(C3H4N2)(O2CCH=CHCO2Zn)]n, which was originally described in the acentric Pc space group (Liu et al., Chin. J. Struct. Chem. 2004, 23, 160～163), is re-described in the centric P21/c space group.

Space Group Distribution in Substituted Phenols

Analysis on the space group distribution in 78 substituted phenols re-vealed its unusual high frequencies in groups with non-centrosymmetry or polar axis orhigher symmetry or Z' > 1. Based on the characteristics of intermolecular H-bondsformed by two OH groups,the space group distribution could be rationalized well.

THE RELATIONSHIP BETWEEN THE INVASION OF PARAPHARYNGEAL SPACES AND THE INVOLVEMENT OF CERVICAL NODES AND POSTERIOR GROUP CRANIAL NERVES IN NASOPHARYNGEAL CARCINOMA

Two hundred cates of nasopharyngeal carcinoma (NPC) admitted to this department from Feb. 1985 to May. 1988 were analysed according to the CT scanning and clinical findings of the primary lesions prior to radiotherapy. The results showed that involvement of parapharyngeal space was very common in NPC, about 80% (160/200 cases) ; particularly unilateral or bilateral retro-styloid spaces, about 69.5% (139/200 cases). It was proposed that patients with NPC had a high Incidence of ipsilateral cervical node metastasis. Contralateral cervical node metastasis was rare. The development of cervical node metastasto in NPC has two modes: one Is direct Infiltration of the retro-stylold space by the lesion; the other Is along the nasopharyngeal lymphatic rete. The data also showed that patients with NPC who presented symptoms of Ⅸ- Ⅲ cranial nerve paralyses always had ipsilateral or bilateral retro- styloid space Infiltrations.

China Jiangnan Space Industry Group

The China Jiangnan Space Industry Group (CJSIG) is subordinate to the China Space Industry Corporation. On the approval of the State Planning Commission, the State Commission for Restructuring the Economy, and the Economic and Trade Office of the State Council, it was established in 1992, an enterprise group with the China Jiangnan Space Industry Group Corporation as a core enterprise, be-

MULTIPLIERS ON WEIGHTED FUNCTION SPACES OVER LOCALLY COMPACT VILENKIN GROUPS

In this note, we consider the multipliers on weighted function spaces over totally disconnected locally compact abelian groups (Vilenkin groups). Firstly we show an (H1 ,L ) multiplier result. We also give an (Hap ,Hap) multiplier result under a similiar condition of Lu Yang type. In section 2, we obtain a result about the boundedness of multipliers on weighted Besov spaces.

Endpoints of Multi-Valued Weak Contractions on the Metric Space of Partially Ordered Groups

The present work considers the endpoint in the abstract metric space. It firstly introduces the metric space of partially ordered groups and the metric space of partially ordered modules, respectively;and defines the convergence of sequences and the multi-valued weak contractions, etc., on the introduced space. And then, with the methods of functional analysis and abstract algebra, it successively establishes an endpoint theorem for the metric space of partially ordered groups and an endpoint theorem for the metric space of partially ordered modules. The contributions of this article extend the theory of cone metric space constructed by Huang and Zhang (2007) and some recent results on the fixed point and endpoint theory, such as the endpoint theorem given by Amini-Harandi (2010).

Crystal Structure of Natural Non-metamict Ti- and Fe^(2+)-rich Chevkinite-(Ce)

The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single -crystal sample collected from Bayan Obo, Inner Mongolia, China. The chemical formula of the sample is Ce4Fe2Ti3Si4O22. The crystals are monoclinic with the unit cell parameters a = 13.4656(15) ?, b = 5.7356(6) ?, c = 11.0977(12) ?, β= 100.636(2)o, V = 842.39 (16) ?3 and Z = 2. The structures of Ti- and Fe2+-rich chevkinite-(Ce) were refined with space groups P21/a and C2/m. Least-squares refinement results show that both structural models of Ti- and Fe2+-rich chevkinite-(Ce) are very good, R[F2>2σ(F2)] =0.027 with P21/a and R[F2>2σ(F2)] =0.021 with C2/m. In order to illustrate the relationship between the two space groups P21/a and C2/m, the distribution of diffraction intensities was inspected. Pseudo extinction was found, i.e., reflections with h+k=2n are systematically strong, while those with h+k=2n+1 are weak. By neglecting the systematically weak (h+k=2n+1) reflections the space group becomes C2/m. There is a mirror plane in the C2/m perpendicular to the b axis. However, oxygen atoms in the P21/a model are of a symmetrical relationship with the corresponding pseudo mirror plane. It is concluded that the crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) is a superstructure with the space group of P21/a, which is of pseudo symmetry corresponding to the space group C2/m.

Preparation and Characterization of Nano-ZnO Precursor for the Antibacterial Activity against Thielaviopsis paradoxa

[Objectives]The paper was to explore a new method for preparing nano ZnO particles.[Methods]A mixture of 2,6-di(2′,4′-dicarboxylphenyl)pyridine(0.05 mM),Zn(NO_(3))2·6H_(2)O(0.1 mM)were added to the solution of DMA(3 mL)and H_(2)O(3 mL),and heated at 90℃for 12 h.The PXRD,TGA and fluorescence properties were characterized.[Results]Transparent block crystals of the[Zn_(2)(2,6-ddpp)(DMA)_(3)(H_(2)O)·H_(2)O]n were obtained(yield 85.4%,based on Zn).The Zn-MOF framework would collapse to form ZnO particles when the temperature exceeded 350℃.[Conclusions]A new Zn(II)-MOF is successfully constructed,and the compound exhibits monoclinic P21/c space group.The results will provide a theoretical basis for the preparation of nano ZnO.

Preparation and Structural Properties of ZnAlxFe2-xO4 Spinel Oxide

The ZnAlxFe2-xO4 (x = 0.0, 0.2 and 0.4) spinel ferrites were prepared by the conventional solid state reaction in air at 1350°C. The X-ray diffraction of all the three samples showed sharp Bragg peaks indicating the formation of a single phase spinel structure. The lattice parameters of the samples were determined from the X-ray diffraction data using the Nelson-Riley extrapolation method. The lattice parameters, cation distribution and oxygen position parameters have also been determined by refining the data by the Rietveld method. Rietveld refinement of the XRD data reveals all the samples to possess cubic symmetry corresponding to the space group Fd3m. Lattice parameters were found to decrease with increasing Al concentration, i.e. 8.4322, 8.4002, and 8.3984 Åfor x = 0.0, 0.2 and 0.4, respectively.

Novel strategy for space group determination in real space

Traditional space group determination methods are all in reciprocal space,which involves ambiguous identification on some space groups which have glide plane and screw axes.The novel strategy herein for space group determination in real space is based on the atom resolution high angle annular dark field(HAADF)technology.Three HAADF images in three specific crystal zone axes are needed at most.The proposed strategy for space group determination is easy and effective.

Air-Stable Dy(III)-Macrocycle Enantiomers:From Chiral to Polar Space Group

Magnetoelectric(ME)multiferroic materials have unique advantages in low-power and high-density information storage,because they can simultaneously display ferroelectricity and ferromagnetism.However,research on how to construct air-stable highperformance ME single-molecule magnets(SMMs)is nonexistent.Herein,by introducing homochirality while reducing molecular symmetry,two doubledecker Dy(III)enantiomers adopting the polar space group P2_(1) and exhibiting excellent thermal stability were obtained.They displayed zero field SMM behavior with an anisotropy barrier(Ueff)of ca.100 cm^(−1).This work establishes a rational chemical design strategy for crystallizing SMMs in polar space groups and elucidates the direction for future research,that is,engineering small-size high-performance SMMs.

Estimation of ballistic coefficients of space debris using the ratios between different objects

This paper proposes a new method to estimate the ballistic coefficient（BC） of low earth orbit space debris.The data sources are the historical two-line elements（TLEs）.Since the secular variation of semi-major axes is mainly caused by the drag perturbation for space objects with perigee altitude below 600 km,the ballistic coefficients are estimated based on variation of the mean semi-major axes derived from the TLEs.However,the approximate parameters used in the calculation have error,especially when the upper atmosphere densities are difficult to obtain and always estimated by empirical model.The proportional errors of the approximate parameters are cancelled out in the form of ratios,greatly mitigating the effects of model error.This method has been also been validated for space objects with perigee altitude higher than 600 km.The relative errors of estimated BC values from the new method are significantly smaller than those from the direct estimation methods used in numerical experiments.The estimated BC values are used for the prediction of the semi-major axes,and good performance is obtained.This process is also a feasible method for prediction over a long period of time without an orbital propagator model.

Characteristic conditions-for strongly continuous groups of linear operators on a Hilbert space

IN 1932, Stone [1] gave the first result concerning C0 semigroups generated by an unbounded operator,which says that a linear operator is the infinitesimal generator of a C0 group of unitary operators on a Hilbert space if and only if it is skew-adjoint. This result has been applied extensively to linear partial differential equations （PDEs） with a law of conservation. Hille [2] then discovered the generation theorem of the Hille-Yosida type for a C0 group on a Banach space. There are also some conditions under which a C0 semigroup on a Banach space can be embedded in a C0 group. We refer the readers to ref. [3] for details of the results mentioned above.

Krein space representation and Lorentz groups of analytic Hilbert modules

This paper aims to introduce some new ideas into the study of submodules in Hilbert spaces of analytic functions. The effort is laid out in the Hardy space over the bidisk H^2(D^2). A closed subspace M in H^2(D^2) is called a submodule if ziM ? M(i = 1, 2). An associated integral operator(defect operator) CM captures much information about M. Using a Kre??n space indefinite metric on the range of CM, this paper gives a representation of M. Then it studies the group(called Lorentz group) of isometric self-maps of M with respect to the indefinite metric, and in finite rank case shows that the Lorentz group is a complete invariant for congruence relation. Furthermore, the Lorentz group contains an interesting abelian subgroup(called little Lorentz group) which turns out to be a finer invariant for M.

Symmetry-enforced two-dimensional Dirac node-line semimetals

Based on symmetry analysis and lattice model calculations,we demonstrate that Dirac nodal line(DNL)can stably exist in two-dimensional(2D)nonmagnetic as well as antiferromagnetic systems.We focus on the situations where the DNLs are enforced by certain symmetries and the degeneracies on the DNLs are inevitable even if spin–orbit coupling is strong.After thorough analysis,we find that five space groups,namely 51,54,55,57 and 127,can enforce the DNLs in 2D nonmagnetic semimetals,and four type-III magnetic space groups(51.293,54.341,55.355,57.380)plus eight type-IV magnetic space groups(51.299,51.300,51.302,54.348,55.360,55.361,57.387 and 127.396)can enforce the DNLs in 2D antiferromagnetic semimetals.By breaking these symmetries,the different 2D topological phases can be obtained.Furthermore,by the first-principles electronic structure calculations,we predict that monolayer YB4C4 is a good material platform for studying the exotic properties of 2D symmetry-enforced Dirac node-line semimetals.