A cocrystal of 3α-hy­droxy­tirucalla-8,24-dien-21-oic acid and 3β-fluoro­tirucalla-7,24-dien-21-oic acid (0.897:0.103)

The title compound, 0.897C30H48O3.0.103C30H47O2F is a co-crystal of two triterpenes isolated from the resin of Canarium schweinfurthiiand Engl. Both triterpenes consists of four trans-fused rings having chair/half-chair/half-chair and envelope conformations. The mol­ecular conformations are stabilized by intra­molecular C—H⋯O hydrogen bonds, forming rings of S(7) graph-set motif. In the crystal, mol­ecules are linked by inter­molecular O—H⋯O and C—H⋯O inter­actions, forming sheets parallel to (001). All atoms. excepting the axially-oriented hydroxyl group in the major component and the equatorially-oriented fluorine atom in the minor component, are overlapping

A Unifying Variational Framework for Gaussian Process Motion Planning

To control how a robot moves, motion planning algorithms must compute paths in high-dimensional state spaces while accounting for physical constraints related to motors and joints, generating smooth and stable motions, avoiding obstacles, and preventing collisions. A motion planning algorithm must therefore balance competing demands, and should ideally incorporate uncertainty to handle noise, model errors, and facilitate deployment in complex environments. To address these issues, we introduce a framework for robot motion planning based on variational Gaussian Processes, which unifies and generalizes various probabilistic-inference-based motion planning algorithms. Our framework provides a principled and flexible way to incorporate equality-based, inequality-based, and soft motion-planning constraints during end-to-end training, is straightforward to implement, and provides both interval-based and Monte-Carlo-based uncertainty estimates. We conduct experiments using different environments and robots, comparing against baseline approaches based on the feasibility of the planned paths, and obstacle avoidance quality. Results show that our proposed approach yields a good balance between success rates and path quality

3α-Hy­droxy­tirucalla-8,24-dien-21-oic acid

The title compound, C30H48O3, a triterpene isolated from the resin of canarium schweinfurthiiand, is an isomer of the previously reported triterpene 3α-hy­droxy­tirucalla-7,24-dien-21-oic acid [Mora et al. (2001 ▶). Acta Cryst. C57, 638–640], which crystallizes in the same trigonal space group. The title mol­ecule consists of four fused rings having chair, half-chair, half-chair and envelope conformations for rings A, B, C and D, respectively (steroid labelling). An intra­molecular C—H⋯O hydrogen bond generates an S(7) ring. In the crystal, mol­ecules are linked by O—H⋯O and C—H⋯O inter­actions, forming (001) sheets

Rh-POP Pincer Xantphos Complexes for C-S and C-H Activation. Implications for Carbothiolation Catalysis

The neutral Rh­(I)–Xantphos complex [Rh­(κ³-_P,O,P-Xantphos)­Cl]_<i>n</i>, <b>4</b>, and cationic Rh­(III) [Rh­(κ³-_P,O,P-Xantphos)­(H)₂]­[BAr^F₄], <b>2a</b>, and [Rh­(κ³-_P,O,P-Xantphos-3,5-C₆H₃(CF₃)₂)­(H)₂]­[BAr^F₄], <b>2b</b>, are described [Ar^F = 3,5-(CF₃)₂C₆H₃; Xantphos = 4,5-bis­(diphenylphosphino)-9,9-dimethylxanthene; Xantphos-3,5-C₆H₃(CF₃)₂ = 9,9-dimethylxanthene-4,5-bis­(bis­(3,5-bis­(trifluoromethyl)­phenyl)­phosphine]. A solid-state structure of <b>2b</b> isolated from C₆H₅Cl solution shows a κ¹-chlorobenzene adduct, [Rh­(κ³-_P,O,P-Xantphos-3,5-C₆H₃(CF₃)₂)­(H)₂(κ¹-ClC₆H₅)]­[BAr^F₄], <b>3</b>. Addition of H₂ to <b>4</b> affords, crystallographically characterized, [Rh­(κ³-_P,O,P-Xantphos)­(H)₂Cl], <b>5</b>. Addition of diphenyl acetylene to <b>2a</b> results in the formation of the C–H activated metallacyclopentadiene [Rh­(κ³-_P,O,P-Xantphos)­(ClCH₂Cl)­(σ,σ-(C₆H₄)­C­(H)CPh)]­[BAr^F₄], <b>7</b>, a rare example of a crystallographically characterized Rh–dichloromethane complex, alongside the Rh­(I) complex <i>mer</i>-[Rh­(κ³-_P,O,P-Xantphos)­(η²-PhCCPh)]­[BAr^F₄], <b>6</b>. Halide abstraction from [Rh­(κ³-_P,O,P-Xantphos)­Cl]_<i>n</i> in the presence of diphenylacetylene affords <b>6</b> as the only product, which in the solid state shows that the alkyne binds perpendicular to the κ³-POP Xantphos ligand plane. This complex acts as a latent source of the [Rh­(κ³-_P,O,P-Xantphos)]⁺ fragment and facilitates <i>ortho</i>-directed C–S activation in a number of 2-arylsulfides to give <i>mer</i>-[Rh­(κ³-_P,O,P-Xantphos)­(σ,κ¹-Ar)­(SMe)]­[BAr^F₄] (Ar = C₆H₄COMe, <b>8</b>; C₆H₄(CO)­OMe, <b>9</b>; C₆H₄NO₂, <b>10</b>; C₆H₄CNCH₂CH₂O, <b>11</b>; C₆H₄C₅H₄N, <b>12</b>). Similar C–S bond cleavage is observed with allyl sulfide, to give <i>fac</i>-[Rh­(κ³-_P,O,P-Xantphos)­(η³-C₃H₅)­(SPh)]­[BAr^F₄], <b>13</b>. These products of C–S activation have been crystallographically characterized. For <b>8</b> in situ monitoring of the reaction by NMR spectroscopy reveals the initial formation of <i>fac</i>-κ³-<b>8</b>, which then proceeds to isomerize to the <i>mer</i>-isomer. With the <i>para</i>-ketone aryl sulfide, 4-SMeC ₆H₄COMe, C–H activation <i>ortho</i> to the ketone occurs to give <i>mer</i>-[Rh­(κ³-_P,O,P-Xantphos)­(σ,κ¹-4-(COMe)­C₆H₃SMe)­(H)]­[BAr^F₄], <b>14</b>. The temporal evolution of carbothiolation catalysis using <i>mer</i>-κ³-<b>8</b>, and phenyl acetylene and 2-(methylthio)­acetophenone substrates shows initial fast catalysis and then a considerably slower evolution of the product. We suggest that the initially formed <i>fac</i>-isomer of the C–S activation product is considerably more active than the <i>mer</i>-isomer (i.e., <i>mer</i>-<b>8</b>), the latter of which is formed rapidly by isomerization, and this accounts for the observed difference in rates. A likely mechanism is proposed based upon these data

Bis(2-amino­thia­zolium) succinate succinic acid

In the title compound, 2C3H5N2S+·C4H4O4 2−·C4H6O4, the thia­zolium ring is almost planar, with the maximum deviation from planarity being 0.0056 (8) Å for the C atom carrying the amine substituent. The N atom of the 2-amino­thia­zole mol­ecule is protonated. Both the anion and the acid lie across inversion centres. The crystal packing is consolidated by inter­molecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. Mol­ecules are stacked down the b axis

2-Ethyl­piperidinium chloride

In the title molecular salt, C7H16N+·Cl−, the piperidinium ring adopts a chair conformation. In the crystal, the two components are connected by N—H⋯Cl and C—H⋯Cl hydrogen bonds, forming a supra­molecular double-chain structure along the c axis

Political transition and emergent forest-conservation issues in Myanmar.

Political and economic transitions have had substantial impacts on forest conservation. Where transitions are underway or anticipated, historical precedent and methods for systematically assessing future trends should be used to anticipate likely threats to forest conservation and design appropriate and prescient policy measures to counteract them. Myanmar is transitioning from an authoritarian, centralized state with a highly regulated economy to a more decentralized and economically liberal democracy and is working to end a long-running civil war. With these transitions in mind, we used a horizon-scanning approach to assess the 40 emerging issues most affecting Myanmar's forests, including internal conflict, land-tenure insecurity, large-scale agricultural development, demise of state timber enterprises, shortfalls in government revenue and capacity, and opening of new deforestation frontiers with new roads, mines, and hydroelectric dams. Averting these threats will require, for example, overhauling governance models, building capacity, improving infrastructure- and energy-project planning, and reforming land-tenure and environmental-protection laws. Although challenges to conservation in Myanmar are daunting, the political transition offers an opportunity for conservationists and researchers to help shape a future that enhances Myanmar's social, economic, and environmental potential while learning and applying lessons from other countries. Our approach and results are relevant to other countries undergoing similar transitions

2,6-Difluoro­benzoic acid

In the title compound, C7H4F2O2, the dihedral angle between the benzene ring and the carboxyl­ate group is 33.70 (14)°. In the crystal structure, inversion dimers linked by pairs of O—H⋯O hydro­gren bonds occur, generating R 2 2(8) loops. The dimers are linked into sheets lying parallel to (102) by C—H⋯F hydrogen bonds

N,N′-[4,4′-Methyl­enebis(4,1-phenyl­ene)]bis­(2,6-difluoro­benzamide)

The complete mol­ecule of the title compound, C27H18F4N2O2, is generated by crystallographic twofold symmetry, with one C atom lying on the rotation axis. The dihedral angle between fluoro-substituted phenyl ring and the adjacent benzene ring is 10.37 (5)°. In the crystal, mol­ecules are connected by N—H⋯O and C—H⋯F hydrogen bonds, resulting in supra­molecular chains propagating along the c direction

Monoclinic polymorph of poly[aqua(μ4-hydrogen tartrato)sodium]

A monoclinic polymorph of the title compound, [Na(C4H5O6)(H2O)]n, is reported and complements an ortho­rhom­bic form [Kubozono, Hirano, Nagasawa, Maeda & Kashino (1993 ▶). Bull. Chem. Soc. Jpn, 66, 2166–2173]. The asymmetric unit contains a hydrogen tartrate anion, an Na+ cation and a water mol­ecule. The Na+ ion is surrounded by seven O atoms derived from one independent and three symmetry-related hydrogen tartrate anions, and a water mol­ecule, forming a distorted penta­gonal–bipyramidal geometry. Independent units are linked via a pair of inter­molecular bifurcated O—H⋯O acceptor bonds, generating an R 2 1(6) ring motif to form polymeric two-dimensional arrays parallel to the (100) plane. In the crystal packing, the arrays are linked by adjacent ring motifs, together with additional inter­molecular O—H⋯O inter­actions, into a three-dimensional network