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The ores of non-ferrous and precious metals, represented by hard rocks, has a peculiar feature, that is the effect of segregation, that is the tendency of ore minerals to break down into small size classes, which in the underground mining method accumulate in significant quantities on uneven surface of bottom layers and subsequently are lost. When mining valuable non-metallic materials, there is an acute problem of overgrinding, when fines do not meet the requirements for the quality of the final product. It is well known that the granulometric composition of the ore depends mainly on the technology and parameters of drilling and blasting operations. In underground mining of ore deposits, the main method of drilling and blasting is the borehole blasting with continuous construction charges with the ring pattern. The main drawbacks of the method are: uneven distribution of the explosive along the plane of the broken layer and the expenditure of a significant part of the blast energy of the charges of the continuous structure on the blasting effect, necessarily associated with over-grinding the ore. To solve these problems, the authors proposed a blasting technology, the essence of which lies in the fact that the uniform distribution of the energy concentration of explosives in the broken layer is ensured by the dispersion of charges by air gaps and a certain order of their placement in the ring plane. For the practical implementation of the technology, a method has been developed to form dispersed charges in deep boreholes that do not require a significant increase in labor costs and additional special means. A special technique has been created that allows defining the dispersion parameters, ensuring the sustained specific consumption of explosives over the entire plane of the broken layer. Experimental studies of the proposed technology in the natural conditions of an underground mine for the extraction of valuable granulated quartz were carried out. As a result, the possibility of a significant reduction in the specific consumption of explosives (by 42 %) has been established. At the same time, the yield of the commercial product increased by 10.7 % in total, and the yield of the fraction most favorable for further processing increased by 33.7 %.

Ever since the discovery of the new antibiotic teixobactin, studies of its structure–activity relationships have never ceased. Here we focus on the chirality of the threonine (Thr) residue, which belongs to the ring motif of teixobactin and plays an important role in the binding with its target, lipid II molecule. We study the structural propensity of the open and closed ring motifs with different chiral Thr residues as well as the teixobactin–lipid II complex with the help of molecular dynamics simulations. Our results suggest that different chiralities lead to different NH orientations of Thr with respect to the ring plane. Only in the closed ring motif with d-Thr is a favored binding cavity achievable with all four NH groups facing the same side of the ring plane. This study develops a deeper understanding of the binding mechanism of teixobactin and lipid II and is expected to be beneficial to new teixobactin-based drug design. National Medical Research Council (NMRC) National Supercomputing Centre (NSCC) Singapore Accepted version We are grateful for financial support from a Singapore Ministry of Education Academic Research Fund Tier 3 Grant (MOE2013-T3-1-002), the Singapore Ministry of Health Industry Alignment Fund (NMRC/MOHIAFCAT2/003/2014), and an MOE Tier 1 Grant (RG 146/17). We also thank the National Supercomputing Centre (NSCC), Singapore, for providing computational resources. Y.L. acknowledges the support of Ph.D. Research Scholarships from MOE.

In the title compound, C10H11N3O6, the torsion angles about the bonds to the benzene ring are less than 4°, except for the nitro groups, which are twisted out of the ring plane by 25.27 (3) and 43.63 (2)°. The N—H group forms a bifurcated hydrogen bond, with an intramolecular component to a nitro group O atom and an intermolecular component to the other nitro group, thereby forming chains propagating in the [010] direction. Several weak C—H...O interactions are also present.

The title compound, C16H16N2, was synthesized by dispersing 3,4-hexanedione in a methanol–water solution containing the acid catalyst NH4HF2, then adding 1,2-diaminonaphthalene. The fused-ring system of the title compound is close to planar (r.m.s. deviation = 0.028 Å); one of the pendant methyl C atoms lies close to the ring plane [deviation = 0.071 (2) Å; N—C—C—C = −0.27 (18)°] whereas the other is significantly displaced [–1.7136 (18) Å; 91.64 (16)°]. The molecules pack in space group I\overline{4} in a distinctive criss-cross motif supported by numerous aromatic π–π stacking interactions [shortest centroid–centroid separation = 3.5805 (6) Å].

Knowledge of the anatomy of the membranous septum, as a surrogate to the location of the atrioventricular conduction axis, is a prerequisite for those undertaking transcatheter implantation of the aortic valve (TAVI). Equally important is its relationship of the virtual basal ring. This feature, however, has yet to be adequately described in the living heart. We analyzed computed tomographic angiographic datasets from 107 candidates (84.1 ± 5.2 years, 68% women) for TAVI. Using multiplanar reconstructions, we measured the height and width of the membranous septum, and the distances of its superior and inferior margins from the virtual basal ring plane. We also assessed the extent of wedging of the aortic root between the mitral valve and the ventricular septum. Mean heights and widths of the membranous septum were 6.6 ± 2.0, and 10.2 ± 3.1 mm, respectively, with its size significantly associated with that of the aortic root (P < 0.05). Its superior and inferior margins were 4.5 ± 2.3 and 2.1 ± 2.1 mm, respectively, from the plane of the basal ring. The inferior distance, the surrogate for the adjacency of the atrioventricular conduction axis, was ≤ 5mm in 91% of the patients. Deeper wedging of the aortic root was independently correlated with a shorter inferior distance (β = 0.0569, P = 0.0258). The membranous septum is appreciably closer to the virtual basal ring than previously appreciated. These findings impact on estimations of the risk of damage to the atrioventricular conduction axis during TAVI. Clin. Anat. 31:525-534, 2018. © 2018 Wiley Periodicals, Inc.

Conformational properties and molecular structure of 1-methyl-1-phenylsilacyclohexane 1 were studied by quantum chemical (QC) calculations, combined gas electron diffraction/mass spectrometry (GED/MS) and IR spectroscopy. Molecule 1 may exist in four forms that differ by axial or equatorial positions of the substituents and by relative orientation of the two rings. Two of these conformers were found to dominate in the gas phase: 1 -Ph eq -orth conformer with the phenyl ring plane bisecting the CSiC endocyclic angle, and 1 -Ph ax -twist with the phenyl ring and the CSiC exocyclic angle oriented nearly perpendicularly to each other. From the GED data, the summarized molar fractions of the conformers were found to be Ph eq :Ph ax = 42(15):58(15)% which corresponds to Δ G = G eq – G ax = 0.19(37) kcal/mol. Experimental and calculated IR spectra provides an evidence of existence of both conformers in the liquid phase. The QC calculations yielded the Δ G = G (Ph eq –orth)– G (Ph ax –twist) values of 0.18–0.36 DFT and 0.82 MP2 kcal/mol.

Washing is a standard step for enzyme-linked immunosorbent assays (ELISA) performed on a paper-based chip, in which nonspecific-binding antibodies and antigens should be removed completely from the paper surface. In this study, a novel three-dimensional (3D) washing strategy using a heating ring-oven was carried out on a paper-based chip. Compared with a plane washing mode by a ring-oven, this 3D washing strategy obtained a lower background, as gravity played an important role in the washing step. The paper-based chip was placed on a 3D plastic holder and the waste area was connected to a heating ring. Use of a heating waste area meant that the nonspecific-binding protein was continuously carried to the waste area through gravity and capillary action. The angle between the plastic holder and the ring plane was carefully selected. The effect of washing on different parts of the detection area was investigated by upconversion fluorescence and chemiluminescence (CL). This novel 3D washing strategy was performed for carcinoembryonic antigen detection through CL and a lower detection limit of 2 pg ml-1 was obtained. This approach provides an effective washing strategy to remove nonspecific-binding antibody from a paper-based immunodevice.

In this work, the aromaticity of polycyclic benzene rings was evaluated by the calculation of g-factor for a hydrogen placed perpendicularly at geometrical center of related ring plane at a distance of 1.2 A. The results have compared with the other commonly used aromatic indices, such as HOMA, NICSs, PDI, FLU, MCI, CTED and, generally been found to be in agreement with them. So, it was proposed that the calculation of the average g-factor as Δg could be applied to study the aromaticity of polycyclic benzene rings without any restriction in the number of benzene rings as a new magnetic-based aromaticity index.

In the title compound, C15H22O4, the fully substituted benzene ring carries a methyl propanoate, two methoxy and three methyl substituents. Both methoxy substituents are almost orthogonal to the benzene ring plane. The methyl propanoate group is almost planar, r.m.s. deviation 0.0138 Å, and is inclined to the benzene ring plane by 80.26 (14)°. In the crystal, C—H...O hydrogen bonds form head-to-tail chains of molecules along theb-axis direction that are supported by very weak C—H...π(ring) contacts.

Highly reduced [Cp3Ln3(μ2-H)3]−/0 (Ln = La or Lu; Cp = C5H5−) clusters “free” from host carbon cages were used as models to mimic the electronic structure of La3@C110 and Lu3@C80 EMFs. DFT calculations revealed that these clusters “unshielded” from host carbon cages are highly reactive, disrupting strong single H–H, H–X (X = F, Cl, Br, and I) and double O=O bonds and descending the inert N≡N triple bond up to a single N–N bond, yielding stable bicapped trinuclear [Cp3Ln3(μ2-H)3(μ3-H)2]−, [Cp3Ln3(μ2-H)3(μ3-H)(μ3-X)]−, [Cp3Ln3(μ2-H)3(μ3-O)2]−, and [Cp3Ln3(μ2-H)3(μ3-N)2]− clusters. The calculated thermodynamics of the reactions revealed an unprecedented reactivity pattern inherent to multimetallic cooperative effect on nonclassic oxidative addition reactions which proceed by electrophilic attack of the oxidative addition (oxad) substrates at the center of the highly reduced triangular trilanthanide Ln3 rings accompanied by “penetration” of the ring plane that cuts the strong bonds. The [Cp3Ln3(μ2-H)3]−/0 (Ln...

In the title compound, C17H14O3, the methyl-substituted benzene ring is twisted relative to the 4H-chromenon skeleton by 51.5 (2)°. The C atom of the methoxy group of the 4H-chromenon unit is displaced from the ring plane by 1.225 (2) Å. In the crystal, C—H—O interactions connect the molecules into (001) sheets.

In this Letter we demonstrate that the quadrupole moment (Qzz) of aromatic compounds shows a strong correlation with the MEP value computed along the main symmetry axis perpendicular to the ring plane. The Qzz value correlates well with both the LUMO energy level and the dipoles created by the substituents. Latter result allows conciliating two different points of view regarding the source of the electrostatic contribution to the total interaction energy ion–π complexes of substituted benzenes. The ethynyl group presents a strange behavior that is analyzed in this Letter, using several tools including MEP and SAPT analysis among others.

In the structure of the titleN,N′-bis(substituted)oxamide compound, C11H13ClN2O4, the chlorohydroxyphenyl ring plane subtends an angle of 15.06 (13)° to the plane of the oxalamide unit. This in turn is inclined to the hydroxypropyl substituent by 78.03 (14)°. In the crystal, classical O—H...O and N—H...O hydrogen bonds give rise to a three-dimensional supramolecular structure.

X-ray measurements of four naphthalene proton sponges have been performed. They include 2,7-di(4-tolylethynyl)-1,8-bis(dimethylamino)naphthalene 4 together with its cation, 2,4-bis(trifluoroacetyl)-1,8-bis(dimethylamino)naphthalenes 16 and 2,6-difluoro-1,3,4,5,7,8-hexakis(dimethylamino)naphthalene 15 . It has been disclosed that among all known proton sponge derivatives, compound 16 possesses the largest N⋯N distance and the strongest deviation of the NMe 2 groups from the average ring plane while for compound 15 the related parameters are record small. A peculiarity of 2,7-diacetylene 4 is its unusually enhanced basicity contrasting with electron acceptor nature of 4-tolylethynyl group. An origin of the latter phenomena is discussed.

Phthalocyanines having hydrophilic or lipophilic dendrons were synthesized to investigate the efficiencies of singlet molecular oxygen (1Δg) formation. The introduction of higher generation of dendrons to the central metal ( Si ) of phthalocyanine in vertical direction to their ring plane has resulted in the successful improvement in avoiding aggregate formation that resulted in efficient generation of 1Δg even in water.

SIREN is a proposed mission concept that would demonstrate the use of small spacecraft at the rings of Saturn to quantify the ring environment and study the composition and dynamics of the ring particles. Many existing small spacecraft technologies are leveraged to make this mission possible. SIREN consists of several daughtercraft deployed from and networked to a mothership in hover-orbit over the ring plane. The mothership is based on the Saturn Ring Observer spacecraft (Nicholson et al., 2010). This paper details the mission objectives, the science requirements, the overall mission design and the science payloads of the daughtercraft.

The structures of sandwich-like and chain-like superatom compounds Li 3 –N 4 –M 3 (M = Li, Na and K) are obtained at the MP2/6-311+G(2d) level. These structures are stable own to large interaction energy ranging from −184.4 to −236.9 kcal/mol. Maximum nucleus-independent chemical shift (NICS max ) values of M 3 + are located at the outside of the M 3 + ring plane about 0.6–1.5 A for the sandwich-like structures, which exhibit unusual out-of-plane σ-aromaticity. The NICS max values of N 4 2− in the sandwich-like structures are obviously larger than that of corresponding chain-like structures, which show that the two adjacent rings (Li 3 + and M 3 + ) enhance the aromaticity of N 4 2− ring in the sandwich-like structures. In addition, the N 4 in the superatom compound is proposed as a new “supersulfur” atom.

To probe the correlation of unusual (C5Me5)(1-) reactivity with steric crowding in complexes such as (C5Me5)3UMe and (C5Me5)3UCl, slightly less crowded (C5Me5)2(C5Me4H)UX analogues (X = Me, Cl) were synthesized and their reactivity was evaluated. The utility of the cationic precursors [(C5Me5)2UMe](1+), 1, and [(C5Me5)2UCl](1+), 2, in the synthesis of (C5Me5)2(C5Me4H)UMe, 3, and (C5Me5)2(C5Me4H)UCl, 4, was also explored. Since the use of precursor [(C5Me5)2UMe][MeBPh3], 1a, is complicated by the equilibrium between 1a and (C5Me5)2UMe2/BPh3, the reactivity of [(C5Me5)2UMe(OTf)]2, 1b, (OTf = O3SCF3) prepared from (C5Me5)2UMe2 and AgOTf, was also studied. Both 1a and 1b react with KC5Me4H to form 3. Complex 4 readily forms by addition of KC5Me4H to [(C5Me5)2UCl][MeBPh3], generated in situ from (C5Me5)2UMeCl and BPh3. Complex 1b was preferred to 1a for the synthesis of (C5Me5)2(C5H5)UMe, 5, and (C5Me5)2UMe[CH(SiMe3)2], 6, from KC5H5 and LiCH(SiMe3)2, respectively. Complex 6 is the first example of a mixed alkyl uranium metallocene complex. Sterically induced reduction (SIR) reactivity was not observed with 3-6 although the methyl displacements from the (C5Me5)(1-) ring plane for 3 are the closest observed to date to those of SIR-active complexes. The (1)H NMR spectra of 3 and 4 are unusual in that all of the (C5Me4H)(1-) methyl groups are inequivalent. This structural rigidity is consistent with density-functional theory calculations.

This is an open-access article distributed under the terms of the Creative Commons Attribution Licence., The title compound, C19H17NO, has an E conformation about the N=C bond. The mol­ecule is relatively planar, with the benzene ring and naphthalene ring plane being inclined to one another by 4.28 (10)°. There is an intra­molecular O—H⋯N hydrogen bond generating an S(6) ring motif. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming chains propagating along [100]. Within the chains there are π–π inter­actions involving the benzene ring and the naphthalene ring system of an adjacent mol­ecule [inter-centroid distance = 3.6405 (14) Å]., We thank the Spanish Ministerio de Economía y Competitividad (MAT2013-40950-R and FPI grants: BES-2011-046948 to author MSMA) and the ERDF for financial support.

The putative dust belts of Mars, a thin equatorial Phobos ring and a thick tilted Deimos torus, whose existence was predicted several decades ago, remain undiscovered. The previous attempt of direct observational detection, undertaken with the Hubble Space Telescope (HST) during the Mars equatorial plane crossing in May 2001, set an upper limit on the normal optical depth to ∼ 3 × 10 - 8 for the Phobos ring and ∼ 10 - 7 for the Deimos torus. This paper analyzes possible reasons for non-detection of the belts and focuses on the next, and the last for three decades to come, natural opportunity to search for the dust belts during the Mars ring plane crossing in December 2007. We have extended our dynamical models to predict the appearance of both dust belts and to estimate the distribution of their optical depth and brightness. Our new calculations show that at least the Deimos dust torus may have escaped HST detection in 2001 only marginally. A thoroughly prepared observational attempt in 2007 with HST, Keck or another comparable telescope will have good chances to discover the Deimos torus, if a detector has a sensitivity by about one order of magnitude better than the one used in 2001. Photometric detection of the Phobos ring appears to be more difficult.

The molecular structure of triphenylamine was studied by gas-phase electron diffraction in combination with ab initio calculations. It is found that in the gas phase at 160°C the molecule possesses C3 symmetry. The principal geometric parameters are as follows (ra structure): N-C 1.421(4), C-Cmean 1.399(1), C-H 1.123(2) A, bond angles NCC 123.6(10)° and 117.2(7)°, and CNC 119.9(2)°. Torsion angles around C-N bonds are −39° and −45°. Phenyl groups are rotated by 48° from the position in which the C3 axis lies in the phenyl ring plane.

Variable 7-carboxylpropoxy or (1-phenyl)ethoxybenzo[b]furan derivatives with (E)- and (Z)-2-alkylcarbamoyl-1-methylvinyl groups at the 2-, 4-, and 5-positions were prepared to find novel and selective leukotriene B(4) (LTB(4)) receptor antagonists. (E)-2-(2-Diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (4v) showed selective inhibition of the human BLT(2) receptor (hBLT(2)). On the other hand, (E)-2-acetyl-4-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (7c) inhibited both human BLT(1) receptor (hBLT(1)) and hBLT(2). The (E)-2-(2-diethylcarbamoyl-1-methylvinyl) group lay on approximately the same plane as the benzo[b]furan ring, whereas the (E)-4-(2-diethylcarbamoyl-1-methylvinyl) group had a torsion angle (45.7 degrees ) from the benzo[b]furan ring plane. However, the (Z)-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans were inactive. The inhibitory activity depended on the conformation of the 2-alkylcarbamoyl-1-methylvinyl groups.

The displacements of the methyl substituents away from the metal and out of the cyclopentadienyl ring plane are compared in sterically crowded (C(5)Me(5))(3)M complexes vs sterically normal f-element complexes in an attempt to evaluate the utility of this parameter in predicting unusual (C(5)Me(5))(1-) ring reactivity. The out-of-plane displacements of 16 sterically crowded tris(cyclopentadienyl) complexes of general formula (C(5)Me(5))(3)M, (C(5)Me(4)R)(3)M (R = Et, (i)Pr, (t)()Bu, SiMe(3)), (C(5)Me(5))(3)MX (X = anion), and (C(5)Me(5))(3)ML (L = neutral ligand) are compared with [(C(5)Me(5))(2)U](2)(C(6)H(6)), (C(5)Me(5))(2)Sm(PC(4)H(2)(t)Bu(2)), and 33 representative examples of f-element bis(cyclopentadienyl) complexes with normal cyclopentadienyl behavior and coordination numbers ranging from 6 to 10. In general, the methyl displacement values of sterically crowded complexes overlap with those in the other complexes, which demonstrates that the basis of the structural distortions is complex. However, if the most extreme out-of-plane displacement in each of the sterically crowded complexes is examined vs the analogous maximum out-of-plane displacement in less crowded systems, there appears to be a basis for predicting cyclopentadienyl reactivity.

Purpose: The Varian tandem and ring applicators are used to deliver HDR Ir-192 brachytherapy for cervical cancer. The source path within the ring is hard to predict due to the larger interior ring lumen. Some studies showed the source could be several millimeters different from planned positions, while other studies demonstrated minimal dosimetric impact. A global shift can be applied to limit the effect of positioning offsets. The purpose of this study was to assess the necessities of implementing a global source shift using Monte Carlo (MC) simulations. Methods: The MCNP5 radiation transport code was used for all MC simulations. To accommodate TG-186 guidelines and eliminate inter-source attenuation, a BrachyVision plan with 10 dwell positions (0.5cm step sizes) was simulated as the summation of 10 individual sources with equal dwell times for simplification. To simplify the study, the tandem was also excluded from the MC model. Global shifts of ±0.1, ±0.3, ±0.5 cm were then simulated as distal and proximal from the reference positions. Dose was scored in water for all MC simulations and was normalized to 100% at the normalization point 0.5 cm from the cap in the ring plane. For dose comparison, Point A was 2 cm caudal from the buildup cap and 2 cm lateral on either side of the ring axis. With seventy simulations, 108 photon histories gave a statistical uncertainties (k=1)

The structure of the first representative of the polynitrothiolene 1,1-dioxide series was studied. Complex analysis of quantum-chemical results, spectral characteristics, and powder X-ray diffraction patterns allowed this compound to be assigned the structure of 3-methyl-2,2,4-trinitro-3-thiolene 1,1-dioxide. The heteroring has an envelope conformation. The sulfur atom slightly deviates from the ring plane, the nitro group attached to the Csp 2 atom is involved in conjugation, and the nitro groups attached to the Csp 3 atom are nonequivalent and perpencular to each other.

A new intercalation compound,Fe0.81PS3(4-aminopyridineH)0.38, issynthesized by the direct reaction of4-aminopyridine with layered FePS3 inthe presence of acetic acid.From the XRD results it was found that there aretwo phases (Phase I and Phase II)in this intercalation compound and that4-aminopyridines as the guests adopt twodifferent orientations between theinterlayer region of the host (FePS3).In one of them with the latticeexpansion (Δd) of 6.0 A thering plane of the guest is perpendicular to thelayer and in the other with Δd of3.4 A the ring plane of the guest is parallel tothe layer of the host. The IR spectraimply that the inserted guests take theprotonated form to maintain the charge balanceof the intercalation compound.Magnetic measurements indicate thatFe0.81PS3(4-aminopyridineH)0.38 exhibitsparamagnetism in the range of measurementtemperature (1.8 ∼: 300 K),where the magnetic behavior is wellin agreement with the Curie-Weiss Lawabove 55 K.

[reaction: see text] The o-quinone methide (2) derived from vitamin E (1) can be stabilized at low temperatures in a complex with the highly polar N-methylmorpholine-N-oxide (5). The lifetime of 2 can thus be prolonged from less than 10 s to several minutes. In the complex formed, 2 adopts a zwitterionic, aromatic structure with the exocyclic methylene group in perpendicular arrangement to the ring plane, stabilized by the negatively charged oxygen in 5.

We both test and offer an alternative to a meteoroid bombardment model (M. R. Showalter 1998, Science282, 1099–1102) and suggest that anomalous localized brightenings in the F ring observed by Voyager result from disruptive collisions involving poorly consolidated moonlets, or “rubble piles.” This model can also explain the transient events observed during ring plane crossing. We have developed an evolutionary model that considers both the competing effects of accretion and disruption at the location of the F ring. Our numerical model is a Markov process where probabilities of mass transfer between the states of the system form a “transition matrix.” Successive multiplications of this matrix by the state vector generate expectation values of the distribution after each time step as the system approaches quasi-equilibrium. Competing effects of accretion and disruption in the F ring are found to lead to a bimodal distribution of ring particle sizes. In fact, our simulation predicts the presence of a belt of kilometer-sized moonlets in the F ring. These moonlets may continually disrupt one another and re-accrete on short time scales. We also agree with J. N. Cuzzi and J. A. Burns (1988, Icarus74, 284–324), who suggest that the classical F ring itself may be the consequence of a relatively recent collision between two of the largest of these yet unseen objects. Cassini observations can confirm the existence of the moonlet belt by directly observing these objects or the waves they create in the rings.

Due to steric effect of the methyl groups the lone electron pair on the nitrogen atom in 3,5-dimethyl-N-phenylsulfonyl-1,4-benzoquinonimine is forced out of the quinoid ring plane, so that the nitrogen atom adopts a near-sp hybridization. As a result, its electrophilicity and hence redox potential increase, leading to activation of the CIN bond to addition of nucleophiles, as compared to the corresponding 2,6-dimethyl isomer.

We have investigated the influence of volumetric (heterocyclic) substituents on the PMR characteristics of substituted nitroanilines depending on their position relative to the nitro group. Using quantum chemical simulation (the PM3 method), data on the position of the proton signals in the PMR spectra of 3-nitro-6-piperidinoaniline and 3-nitro-4-piperidinoaniline are interpreted. It is established that for structures in which the nitro group is removed from the benzene ring plane it does not appear possible to calculate the PMR spectrum using the Beeby–Sternhell increments.

In the title compound, C9H10BrClN2S, the dimethylthiourea group is twisted from the benzene ring plane by 54.38 (6)°. In the crystal, the amino groups are involved in the formation of N—H...S hydrogen bonds, which link the molecules into chains along [010]. Weak C—H...Cl interactions further link these chains into layers parallel to theabplane.

The crystal structure of a polymorph of 4-aminobenzoic acid (PABA), C7H7NO2, at 100 K is noncentrosymmetric, as opposed to centrosymmetric in the structures of the other known polymorphs. The two crystallographically independent PABA molecules form pseudocentrosymmetric O—H...O hydrogen-bonded dimers that are further linked by N—H...O hydrogen bonds into a three-dimensional network. The benzene rings stack in thebdirection. The CO2moieties are bent out slightly from the benzene ring plane.

The ruthenium complexes trans , trans , trans -[RuCl 2 (POMe P ) 2 (FcC 6 H 4 NC) 2 ] ( 1 ) (POMe=PPh 2 C 6 H 4 OCH 3 ; Fc=ferrocenyl) and trans , trans , trans -[RuCl 2 (PC2OMe P ) 2 (FcC 6 H 4 NC) 2 ] ( 2 ) (PC2OMe=PPh 2 CH 2 CH 2 OCH 3 ) have been prepared by reaction of FcC 6 H 4 NC with [RuCl 2 (POMe P , O ) 2 ] ( 5 ) and [RuCl 2 (PC2OMe P , O ) 2 ] ( 6 ), respectively. The mixed carbonyl–isocyanide complexes trans , trans , trans -[RuCl 2 (POMe P ) 2 (CO)(FcC 6 H 4 NC)] ( 3 ) and trans , trans , trans -[RuCl 2 (PC2OMe P ) 2 (CO)(FcC 6 H 4 NC)] ( 4 ) were prepared by sequential reaction of 5 and 6 with carbon monoxide and FcC 6 H 4 NC, respectively. These complexes have all been characterized by 1 H-NMR, 31 P-NMR and infrared spectroscopies as well as microanalysis. The solid-state structure of 1 was determined by X-ray crystallography. All three pairs of ligands are trans in this complex, and the ferrocenyl groups are tilted with respect to the phenyl ring plane by 28°. Cyclic voltammetry of these complexes reveals essentially no electronic interaction occurs between the ferrocenyl groups and the Ru.

This paper presents observations of four inner Saturnian satellites (SX = Janus, SXI = Epimetheus, SXVI = Prometheus and SXVII = Pandora) made in August and November 1995 during the Earth and Sun crossings of Saturn's ring plane, respectively. The August 1995 data combine data taken with the Adonis optics system mounted on the ESO 3.6-m telescope at La Silla, and images from the Hubble Space telescope (HST). The November 1995 data are based on HST images only. Orbits fits show that these observations combined with those of Nicholson et al. ([CITE]) have residuals of about 0.05 arcsec.

The title molecule, C24H25NOSi, is a hydrolysis product of the reaction between 9-trimethylsilyfluorenyl lithium and 2-methoxybenzonitrile. The fluorene ring system is substantially planar, with an r.m.s. deviation of 0.0288 Å from the best-fit plane through its 13 C atoms. This plane forms a dihedral angle of 58.07 (7)° with the 2-methoxybenzylamine ring plane. In the crystal, molecules are linked by N—H...π and C—H...π interactions, which leads to the formation of two-dimensional network lying parallel to the bc plane.

Remarkably short distances to the ring plane are shown by the eta(5)-bound lithium ions in the first compound with a triply negatively charged five-membered ring, 1, which was obtained by reduction of 2 with lithium. R=CH(SiMe(3))(2), Dur=2,3,5,6-tetramethylphenyl.

In the title compound, C6H7N2O+ center dot C2O2F3-, the carboxamide group is twisted by 16.3 (8) degrees from the pyridine ring plane. The protonated cations are linked to the anions by N-H center dot center dot center dot O hydrogen bonds to form a distorted lamellar structure.

The cyclisation of a meta-phenylene-bis-alanine derivative with several different spacer moieties was investigated. A large difference in the ease of cyclisation was observed depending on which path of cyclisation was chosen. NMR studies indicate that the closed-loop molecules adopt folded conformations with the loop directly above the aromatic ring plane.