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A series of nitrogen-rich “green” Energetic Materials (EMs), some with improved sensitivity, thermostability, and very low toxicity, were synthesized on the basis of 3,5-diamino-1,2,4-triazole (DAT) and 1,2,4,5-tetrazine building blocks. Since DAT contains several nucleophilic reactive sites, obtaining selective reactivity and specific isomeric products with 1,2,4,5-tetrazine precursors is a challenging task. We developed reaction conditions under which specific isomers could be prepared. On evaluating these compounds for their energetic properties, we found that N5,N5′-(1,2,4,5-tetrazine-3,6-diyl)-bis(1H-1,2,4-triazole-3,5-diamine) 1 has very high thermostability (onset of decomposition temperature at 357 °C) and it is insensitive to impact (Im ＞ 98 J), friction (＞360 N) and electrostatic discharge (2512 mJ). A detonation velocity (Vod) of 8180 m s−1 was calculated for compound 1 and it was found to have extremely low toxicity in human cells (normal dermal fibroblasts) and in environmental bacteria (Vibrio fischeri). In combination with oxidants, compound 1 can generate 1225 L of gases (per kg of energetic mixture of an oxidant and compound 1), which makes this material a prospective component in solid propellants and a very good candidate for the development of solid state gas generators for clean fire-extinguishing systems and for a broad range of other civil and defense applications that require the use of “green” and insensitive EMs. [ABSTRACT FROM AUTHOR]

3,4-Dihydro-2-amino-6 methyl-4-oxo-5-(4-pyridylthio)-quinazoline dihydrochloride (AG337) is a water-soluble, lipophilic inhibitor of thymidylate synthase (TS) designed using X-ray structure - based methodologies to interact at the folate cofactor binding site of the enzyme. The aim of the design program was to identify TS inhibitors with different pharmacological characteristics from classical folate analogs and, most notably, to develop non-glutamate-containing molecules which would not require facilitated transport for uptake and would not undergo intracellular polyglutamylation. One molecule which resulted from this program, AG337, inhibits purified recombinant human TS with a Ki of 11 nM, and displays non-competitive inhibition kinetics. It was further shown to inhibit cell growth in a panel of cell lines of murine and human origin, displaying an IC50 of between 0.39 microM 6.6 microM. TS was suggested as the locus of action of AG337 by the ability of thymidine to antagonize cell growth inhibition and the direct demonstration of TS inhibition in whole cells using a tritium release assay. The demonstration, by flow cytometry, that AG337-treated L1210 cells were arrested in the S phase of the cell cycle was also consistent with a blockage of TS, as was the pattern of ribonucleotide and deoxyribonucleotide pool modulation in AG337-treated cells, which showed significant reduction in TTP levels. The effects of AG337 were quickly reversed on removal of the drug, suggesting, as would be expected for a lipophilic agent, that there is rapid influx and efflux from cells and no intracellular metabolism to derivatives with enhanced retention. In vivo, AG337 was highly active against the thymidine kinase-deficient murine L5178Y/TK-lymphoma implanted either i.p. or i.m. following i.p. or oral delivery. Prolonged dosing periods of 5 or 10 days were required for activity, and efficacy was improved with twice-daily dose administration. Dose levels of 25 mg/kg delivered i.p. twice daily for 10 days, 50 mg/kg once daily for 10 days, or 100 mg/kg once daily for 5 days elicited 100% cures against the i.p. tumor. Doses required for activity against the i.m. tumor were higher (100 mg/kg i.p. twice daily for 5 or 10 days) but demonstrated the ability of AG337 to penetrate solid tissue barriers. Oral delivery required doses of > or = 150 mg/kg twice daily for periods of 5-10 days to produce 100% cure rates against both i.m. and i.p. implanted tumors. These results were consistent with the pharmacokinetics parameters determined in rats, for which oral bioavailability of 30-50% was determined, together with a relatively short elimination half life of 2h. Clinical studies with AG337 are currently in progress. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) is considered as one of the technological megatrends of 2020s, and today, VR systems are used in various settings, digital gaming being among the most popular ones. However, there has been a dearth of understanding regarding the central factors behind VR gaming acceptance and use. The present study therefore aimed to explain the factors that drive the use and acceptance of VR games. We extended the hedonic-motivation system acceptance model with utilitarian and inconvenience factors to capture the pertinent features of VR systems more holistically. We proposed a theoretical model and analyzed it through covariance-based structural equation modeling using an online survey sample of 473 VR gamers. Our findings help explain the role of different antecedents behind VR gaming acceptance and demonstrate that VR gaming is driven more by the hedonic gaming aspects than by the utilitarian health and well-being aspects of VR games, enjoyment being the strongest driver behind VR gaming intention and immersion. Moreover, findings also suggested that use intentions and immersion levels are not significantly diminished by physical discomfort and VR sickness. The findings, which potentially extend to other VR systems as well, also pose important implications for the providers of VR games. As the main contribution, based on our empirical findings, we provide a greater theoretical understanding on VR gaming acceptance and use., Competing Interests: Conflict of interestThe authors have no relevant financial or non-financial interests to disclose. The authors have no competing interests to declare that are relevant to the content of this article., (© The Author(s) 2023.)

Covid-19 has prompted a surge of data visualizations that have been published for public consumption, yet, many have not had broad appeal or may have not been well-understood by laypeople. A data storytelling platform called Flow Immersive has been created to successfully engage both laypeople and experts in understanding complex information. This tool integrates emerging technologies [e.g., augmented reality (AR) and virtual reality (VR)] with a multiplatform, multiuser publishing approach. From October 2020 to December 2020, Flow's Covid-19 AR videos captured 9 million (9,000,000) views, and have been used in multiple professional presentations. This paper documents the journey from development to deployment, and some user feedback which all led to breakthroughs in scalability and higher levels of engagement., Competing Interests: MD is the cofounder of the company Flow Immersive.The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 DiBenigno, Kosa and Johnson-Glenberg.)

An eight-member series of CF 3 -substituted difluorophosphorus corroles was prepared for establishing a structure-activity profile of these high-potential photosensitizers. It consisted of preparing all four possible isomers of the monosubstituted corrole and complexes with 2-, 3-, 4-, and 5-CF 3 groups on the macrocycle's periphery. The synthetic pathway to these CF 3 -substituted derivatives, beginning with (tpfc)PF 2 , involves two different initial routes: (i) direct electrophilic CF 3 incorporation using FSO 2 CF 2 CO 2 Me and copper iodide, or (ii) bromination to achieve the 2,3,8,17,18-pentabrominated compound using excess bromine in methanol. Crystallographic investigations revealed that distortion of the original planar macrocycle is evident even in the monosubstituted case and that it becomes truly severe for the penta-CF 3 -substituted derivative 5. There is a shift in redox potentials of about 193 mV per -CF 3 group, which decreases to only 120 mV for the fifth one in 5. Differences in the electronic spectra suggest that the Gouterman four orbital model decreases in relevance upon gradual -CF 3 substitution, a conclusion that was corroborated by DFT calculations. The very significant energy lowering of the frontier orbitals suggested that photoexcitation should lead to a highly oxidizing photocatalyst. This hypothesis was proven true by finding that the most synthetically accessible CF 3 -substituted derivative is an excellent catalyst for the photoinduced conversion of bromide to bromine (phenol, toluene, and benzene assay).

Metal-ligand coordination is a key interaction in the self-assembly of both biopolymers and synthetic oligomers. Although the binding of metal ions to synthetic proteins and peptides is known to yield high-order structures, the self-assembly of peptidomimetic molecules upon metal binding is still challenging. Herein we explore the self-assembly of three peptoid trimers bearing a bipyridine ligand at their C-terminus, a benzyl group at their N-terminus, and a polar group (N-ethyl-R) in the middle position (R=OH, OCH 3 , or NH 2 ) upon Cu 2+ coordination. X-ray diffraction analysis revealed unique, highly symmetric, dinuclear cyclic structure or aqua-bridged dinuclear double-stranded peptoid helicates, formed by the self-assembly of two peptoid molecules with two Cu 2+ ions. Only the macrocycle with the highest number of intermolecular hydrogen bonds is stable in solution, while the other two disassemble to their corresponding monometallic complexes., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We describe the construction of synthetically challenging heteroleptic complexes by capitalizing on the solubility properties of their corresponding favored homoleptic complexes. We demonstrate that the formation of a heteroleptic Cu 2+ complex based on 2,2':6',2''-terpyridine (Terpy) and 8-hydroxyquinoline (HQ) is not possible due to the insolubility of (HQ) 2 Cu 2+ . Replacing HQ with 8-hydroxy-2-quinolinecarbonitrile (HQCN) enabled the solubility of (HQCN) 2 Cu 2+ in acetonitrile, leading to the formation of the heteroleptic complex Terpy(HQCN)Cu 2+ , TQCu. Applying these conditions to the synthesis of the corresponding heteroleptic Co 2+ complex resulted in TerpyCo 2+ (acetate) 2 , which is insoluble in acetonitrile. Upon changing the solvent to methanol, the carbonitrile group of HQCN was converted to carboxyimidate HQOMe yielding a heteroleptic complex Terpy(HQOMe)Co 2+ , TQ'Co. Using this method, we also generated the heteroleptic complex TQ'Ni and the polynuclear heteroleptic complex Q'4Q''2Mn4 (Q'' = HQO 2 Me). Detailed analysis of the complexes included characterization by X-ray diffraction, EPR, UV-Vis, high resolution ESI MS, DFT calculations and electrochemistry. X-ray analysis of TQCu revealed distorted square pyramidal geometry, while TQ'Co and TQ'Ni exhibit distorted octahedral geometry, which includes metal coordination via the carboxyimidate nitrogen site. Interestingly, Q'4Q''2Mn4 was found to contain a [Mn(μ 3 -O) 2 (μ 2 -O) 4 N 10 ] 2+ core, which adopts a distorted octahedral geometry, and two types of HQ chelators. Thus, Q'4Q''2Mn4 is also heteroleptic even though it does not contain a Terpy ligand. Solution studies revealed that while TQCu is stable in solution, TQ'Co and TQ'Ni go through ligand exchange and are partially converted to their corresponding homoleptic complexes. Based on these data we could propose a mechanism for the formation of TQ'Co and TQ'Ni and show that TQ'Co can be prepared directly from Terpy and HQOMe.

Palbociclib free base capsule is a weak base drug with highly pH-dependent solubility. In vitro and in vivo studies evaluated the impact of acid-reducing agents on exposure of palbociclib and determined whether the impact, if any, can be mitigated by food. A drug-drug interaction study (study 1) was conducted first under fasted conditions and showed that coadministration of multiple doses of the proton-pump inhibitor rabeprazole substantially reduced palbociclib mean area under the concentration-time curve from time 0 to infinity and maximum observed plasma concentration by 62% and 80%, respectively. In vitro assessment suggested that the presence of bile salt mixed micelles to mimic the fed state can significantly enhance the solubility of palbociclib. Subsequently, study 2 was conducted under fed conditions and demonstrated that coadministration of rabeprazole decreased palbociclib maximum observed plasma concentration by 41% but had limited impact on area under the concentration-time curve from 0 to infinity (13% decrease). This study also showed that the histamine-2 receptor antagonist famotidine and local antacid with staggered dosing had no impact on palbociclib exposure under fed conditions. Food intake effectively mitigated the impact of acid-reducing agents on palbociclib exposure. Palbociclib free base capsule should be taken with food, and acid-reducing agent use does not need to be avoided., (© 2017, The American College of Clinical Pharmacology.)

Gold corroles are not readily accessible and they display no interesting physical or chemical properties. A facile methodology has now been developed for obtaining selectively CF 3 -substituted gold(III) corroles and the introduction of these groups has been found to have an immense effect on the structures of the complexes, their photophysical and redox properties, and on their ability to participate in catalytic processes., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of nitrogen-rich "green" Energetic Materials (EMs), some with improved sensitivity, thermostability, and very low toxicity, were synthesized on the basis of 3,5-diamino-1,2,4-triazole (DAT) and 1,2,4,5-tetrazine building blocks. Since DAT contains several nucleophilic reactive sites, obtaining selective reactivity and specific isomeric products with 1,2,4,5-tetrazine precursors is a challenging task. We developed reaction conditions under which specific isomers could be prepared. On evaluating these compounds for their energetic properties, we found that N 5 ,N 5 '-(1,2,4,5-tetrazine-3,6-diyl)-bis(1H-1,2,4-triazole-3,5-diamine) 1 has very high thermostability (onset of decomposition temperature at 357 °C) and it is insensitive to impact (I m > 98 J), friction (>360 N) and electrostatic discharge (2512 mJ). A detonation velocity (V od ) of 8180 m s -1 was calculated for compound 1 and it was found to have extremely low toxicity in human cells (normal dermal fibroblasts) and in environmental bacteria (Vibrio fischeri). In combination with oxidants, compound 1 can generate 1225 L of gases (per kg of energetic mixture of an oxidant and compound 1), which makes this material a prospective component in solid propellants and a very good candidate for the development of solid state gas generators for clean fire-extinguishing systems and for a broad range of other civil and defense applications that require the use of "green" and insensitive EMs.

A minor modification of the reported procedure for the synthesis of a corrole dimer that is fused by the cyclooctatetraene (COT) unit, (H 3 tpfc) 2 COT, allowed for its isolation in 18% yield. Of the two redox isomers that this interesting macrocycle does form, the current focus is on the reduced form, in which each subunit resembles that of monomeric corroles with a trianionic N 4 coordination core. The corresponding bis-gallium(III) complex was prepared as an entry into the potentially rich coordination chemistry of (H 3 tpfc) 2 COT. Both X-ray crystallography and DFT calculations disclosed that the COT moiety is essentially planar with very unusual nonalternating C-C bonds. The same holds true for the bis-gallium(III) complexes [(Ga-tpfc) 2 ]COT(py) 2 and [(Ga-tpfc) 2 ]COT(py) 4 , obtained with one and two pyridine molecules coordinated to each metal ion, respectively. The electronic spectra of both the free base and the gallium(III) complexes display an extremely low energy band (λ max at 720-724 nm), which points toward extensive π delocalization through the COT bridge. This aspect was fully addressed by examining the interactions between the two corrole subunits in terms of electrochemistry and DFT calculations of the oxidized and reduced macrocycle. The new near-IR bands that appear upon both oxidation (λ max 1250 nm) and reduction (λ max 1780 nm) serve as additional supporting evidence for this conclusion.

The most intriguing feature of metal-metal bonds in inorganic compounds is an apparent lack of correlation between the bond order and the bond length. In this study, we combine a variety of literature data obtained by quantum chemistry and our results based on the empirical bond valence model (BVM), to confirm for the first time the existence of a normal exponential correlation between the effective bond order (EBO) and the length of the metal-metal bonds. The difference between the EBO and the formal bond order is attributed to steric conflict between the (TM)n cluster (TM=transition metal) and its environment. This conflict, affected mainly by structural type, should cause high lattice strains, but electron redistribution around TM atoms, evident from the BVM calculations, results in a full or partial strain relaxation., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ni-rich Li-based layered Ni, Co, and Mn (NCM) materials have shown tremendous promise in recent years as positive electrode materials for Li-ion batteries. This is evident as companies developing batteries for electrical vehicles are currently commercializing these materials. Despite the considerable research performed on LiNiαCoβMnγO2 systems, we do not yet have a complete atomic level understanding of these materials. In this work we study the cationic ordering, thermodynamics, and diffusion kinetics of LiNi0.5Co0.2Mn0.3O2 (NCM-523). Initially, we show that cationic ordering can be predicted employing cheap atomistic simulations, instead of using expensive first-principles methods. Subsequently, we investigate the electrochemical, thermodynamic and kinetic properties of NCM-523 using density functional theory (DFT). Our results demonstrate the importance of including dispersion corrections to standard first principles functionals in order to correctly predict the lattice parameters of layered cathode materials. We also demonstrate that a careful choice of computational protocol is essential to reproduce the experimental intercalation potential trends observed in the LiNi0.5Co0.2Mn0.3O2 electrodes. Analysis of the electronic structure confirms an active role of Ni in the electrochemical redox process. Moreover, we confirm the experimental finding that on complete delithiation, this material remains in an O3 phase, unlike LiCoO2 and NCM-333. Finally, we study various pathways for the Li-ion diffusion in NCM-523, and pinpoint the preferred diffusion channel based on first principles simulations. Interestingly, we observe that the Li diffusion barrier in NCM-523 is lower than that in LiCoO2.

In the current work, pristine α-Fe2O3 metal oxide was doped with Mg in an attempt to modulate its electronic properties. To this end, we employed an experimental high throughput strategy, including scanning XRD and optical spectroscopy, which were complimented by atomistic density functional theory (DFT) calculations. The combined study reveals that at Mg/Fe atomic ratios up to ∼1/3, the bandgaps of the hematite-Mg composite materials are similar to that of the pure material. The observed bandgaps are rationalized by electronic band structure and density of states calculations. Additional rationale for the similar bandgaps in pure and doped hematite is provided by topological Bader charge analyses, which indicate that the Mg and Fe ions in the hematite matrix have similar partial atomic charges. Nonetheless, the small charge density difference between the Mg and Fe ions induces a slight spin polarization on both oxygen and Fe ions, resulting in changes in the band edges. Further charge density analyses, using charge density maps and chemical-bonding analyses with the crystal orbital Hamiltonian population scheme, indicate that Mg forms ionic bonds with the neighboring oxygen atoms. This change from iron-oxygen covalent bonds to a more ionic nature for magnesium-oxygen bonds is probably responsible for the reduction observed in the computed bulk modulus of α-Mg(0.17)Fe(1.83)O3 (193 GPa) compared to α-Fe2O3 (202 GPa).

In the current paper, we present a non-aqueous sol-gel synthesis of olivine type LiCo1-xFexPO4 compounds (x = 0.00, 0.25, 0.50, 0.75, 1.00). The magnetic properties of the olivines are measured experimentally and calculated using first-principles theory. Specifically, the electronic and magnetic properties are studied in detail with standard density functional theory (DFT), as well as by including spin-orbit coupling (SOC), which couples the spin to the crystal structure. We find that the Co(2+) ions exhibit strong orbital moment in the pure LiCoPO4 system, which is partially quenched upon substitution of Co(2+) by Fe(2+). Interestingly, we also observe a non-negligible orbital moment on the Fe(2+) ion. We underscore that the inclusion of SOC in the calculations is essential to obtain qualitative agreement with the observed effective magnetic moments. Additionally, Wannier functions were used to understand the experimentally observed rising trend in the Néel temperature, which is directly related to the magnetic exchange interaction paths in the materials. We suggest that out of layer M-O-P-O-M magnetic interactions (J⊥) are present in the studied materials. The current findings shed light on important differences observed in the electrochemistry of the cathode material LiCoPO4 compared to the already mature olivine material LiFePO4.

The future of affordable fuel cells strongly relies on the design of earth-abundant (non-platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of β-pyrrole-brominated corrole as ORR catalysts. The adsorption of these complexes on a high-surface-area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disclosed a clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co(III) corrole, whose onset potential was as positive as 0.81 V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metabolic synthesis of single cell oils (SCOs) for biodiesel application by heterotrophic oleaginous microorganisms is being hampered by the high cost of culture media. This study investigated the possibility of using loblolly pine and sweetgum autohydrolysates as economic feedstocks for microbial lipid production by oleaginous Rhodococcus opacus (R. opacus) PD630 and DSM 1069. Results revealed that when the substrates were detoxified by the removal of inhibitors (such as HMF-hydroxymethyl-furfural), the two strains exhibited viable growth patterns after a short adaptation/lag phase. R. opacus PD630 accumulated as much as 28.6 % of its cell dry weight (CDW) in lipids while growing on detoxified sweetgum autohydrolysate (DSAH) that translates to 0.25 g/l lipid yield. The accumulation of SCOs reached the level of oleagenicity in DSM 1069 cells (28.3 % of CDW) as well, while being cultured on detoxified pine autohydrolysate (DPAH), with the maximum lipid yield of 0.31 g/l. The composition of the obtained microbial oils varied depending on the substrates provided. These results indicate that lignocellulosic autohydrolysates can be used as low-cost fermentation substrates for microbial lipid production by wild-type R. opacus species. Consequently, the variety of applications for aqueous liquors from lignocellulosic pretreatment has been expanded, allowing for the further optimization of the integrated biorefinery.

First-principles density functional theory (DFT) and a many-body Green's function method have been employed to elucidate the electronic, magnetic, and photonic properties of a spinel compound, Co3O4. Co3O4 is an antiferromagnetic semiconductor composed of cobalt ions in the Co(2+) and Co(3+) oxidation states. Co3O4 is believed to be a strongly correlated material, where the on-site Coulomb interaction (U) on Co d orbitals is presumably important, although this view has recently been contested. The suggested optical band gap for this material ranges from 0.8 to 2.0 eV, depending on the type of experiments and theoretical treatment. Thus, the correlated nature of the Co d orbitals in Co3O4 and the extent of the band gap are still under debate, raising questions regarding the ability of DFT to correctly treat the electronic structure in this material. To resolve the above controversies, we have employed a range of theoretical methods, including pure DFT, DFT+U, and a range-separated exchange-correlation functional (HSE06) as well as many-body Green's function theory (i.e., the GW method). We compare the electronic structure and band gap of Co3O4 with available photoemission spectroscopy and optical band gap data and confirm a direct band gap of ca. 0.8 eV. Furthermore, we have also studied the optical properties of Co3O4 by calculating the imaginary part of the dielectric function (Im(ε)), facilitating direct comparison with the measured optical absorption spectra. Finally, we have calculated the nearest-neighbor interaction (J1) between Co(2+) ions to understand the complex magnetic structure of Co3O4.

Light oil from pyrolysis, which accounts for ∼10 % carbon yield of the starting biomass, is a complex aqueous product that is difficult to utilize and usually discarded. This work presents the feasibility of light oil as a sole carbon source to support the growth of Rhodococcus opacus (R. opacus) that in turn accumulate triacylglycerols as biodiesel feedstock. Two types of bacteria (R. opacus PD630 and DSM 1069) were selected in this study. Research results showed that after short adaption periods both strains can grow well on this complex carbon source, as proved by the consumption of oligomers and monomers in light oil. Lipid content by R. opacus PD630 and DSM 1069 was observed up to 25.8 % and 22.0 % of cell dry weight, respectively. Palmitic and stearic acids were found to be the predominant fatty acids in these bacterial cells. In addition, the light oil-based lipid production can be enhanced by reducing the pH value from 7 to 4, especially in case of DSM 1069.

Upon heating, lithium L-malate undergoes topotactic dehydration to form a phase containing the unsaturated fumarate ligand, in which the original 3-D framework remains intact. Insight into this unusual transformation has been obtained by single crystal X-ray diffraction, MAS-NMR, in situ powder X-ray diffraction and DFT calculations.

Kraft lignin is an inexpensive and abundant byproduct of pulp mills that can be used in the synthesis of adhesives and carbon fibers along with energy production. Some of these material applications favor the utilization of high molecular weight (HMW) lignin. This study investigates the use of ultrasonics as a means to increase the degree of polymerization (DP) of highly purified Kraft lignin. Treated samples were characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, (13)C and (31)P nuclear magnetic resonance (NMR). After 15 min of sustained cavitation, ultrasonicated lignin generated a high molecular-weight fraction (~35%) that had a weight-average molecular weight (Mw) over 450-fold greater than the initial Kraft lignin sample. (13)C-NMR and (31)P-NMR analysis indicated that the highly-polymerized fraction was enriched with C5 condensed phenolic structures., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The observation that (iPr3Si)(tBu3Si)Si: (1) yields an intramolecular C-H bond insertion product at room temperature, together with earlier computational predictions that triplet 1 is slightly more stable (or isoenergetic) than singlet 1 and additional considerations, led previous investigators to conclude that 1 is the first silylene to exhibit triplet electronic state reactivity. In this paper we test, using DFT and ab initio methods, whether the occurrence of intramolecular C-H bond insertion indeed indicates the presence of a triplet-state silylene. DFT calculations at the B3LYP/6-31+G(d,p)//B3LYP/6-31+G(d,p) level show that singlet (iPr3Si)(tBuMe2Si)Si: (9), a close model of singlet 1, inserts intramolecularly into a C-H bond of the tBu group with a barrier of 22.7 kcal/mol (22.2 kcal/mol at SCS-MP2/cc-PVTZ). However, for triplet9 the barrier of this insertion reaction is significantly higher, 34.6 kcal/mol (41.9 kcal/mol at SCS-MP2/cc-PVTZ). This implies that at room temperature the intramolecular insertion reaction of the singlet is 10(9)-10(12) faster than that of the triplet. We conclude, in contrast to previous conclusions, that the observed intramolecular C-H bond insertion reactions of 1 as well as of (tBu3Si)2Si: (2) occur from the singlet state. Furthermore, the occurrence of an intramolecular C-H bond insertion cannot serve as evidence for the presence of a triplet silylene, either in cases where the singlet and triplet states are nearly isoenergetic (e.g., 1 and 9) or even for silylenes where the triplet state is the ground state (e.g., 2), because the corresponding singlet silylenes insert intramolecularly much faster. The search for a genuine reaction of a triplet silylene has to continue.

A 3D hybrid zinc formate framework, [NH(4)][Zn(HCOO)(3)], possessing an acs topology, shows a high degree of mechanical anisotropy and negative linear compressibility (NLC) along its c axis. High-pressure single-crystal X-ray diffraction studies and density functional theory calculations indicate that contraction of the Zn-O bonds and tilting of the formate ligands with increasing pressure induce changes in structure that result in shrinkage of the a and b axes and the NLC effect along c.

Although economically efficient biomass conversion depends on the utilization of the complete cell wall (biorefinery concept), including polysaccharides and lignin, current biofuels research concentrate mostly on cellulose conversion, while lignin is viewed as a side-product that is used primarily as a thermal resource. Microbiological conversion of lignin is almost exclusive to fungi, usually resulting in increased cell mass and lignolytic enzymes. Some bacteria can also degrade lignin-related compounds using the β-ketoadipate pathway; for example, Rhodococcus opacus DSM 1069 can degrade coniferyl alcohol and grow on it as sole carbon source. Moreover, this strain belongs to the actinomycetes group that is also known for oleaginous species with lipid accumulation over 20%. Present work shows that R. opacus DSM 1069 and PD630 strains under nitrogen limiting conditions can convert lignin model compounds into triacylglycerols, also known as neutral lipids. 4-Hydroxybenzoic and vanillic acid lignin model compounds were used as sole carbon sources, and after brief adaptation periods, the cells not only began growing but accumulated lipids to the level of oleaginicity. These lipids were extracted for transesterification and analysis of fatty acid methyl esters showed good composition for biodiesel applications with no aromatics. Furthermore, the two strains showed distinct substrate metabolism and product profiles.

Diminishing fossil fuel resources as well as growing environmental and energy security concerns, in parallel with growing demands on raw materials and energy, have intensified global efforts to utilize wood biopolymers as a renewable resource to produce biofuels and biomaterials. Wood is one of the most abundant biopolymer composites on earth that can be converted into biofuels as well as used as a platform to produce bio-based materials. The major biopolymers in wood are cellulose, hemicelluloses, and lignin which account for >90% of dry weight. These polymers are generally associated with each other in wood cell walls resulting in an intricate and dynamic cell wall structure. This mini-review provides an overview of major wood biopolymers, their structure, and recent developments in their utilization to develop biofuels. Advances in genetic modifications to overcome the recalcitrance of woody biomass for biofuels are discussed and point to a promising future.

Heterotrophic oleaginous microorganisms are capable of producing over 20% of their weight in single cell oils (SCOs) composed of triacylglycerols (TAGs). These TAGs contain fatty acids, such as palmitic, stearic and oleic acids, that are well-suited for biodiesel applications. Although some of these microbes are able to accumulate SCOs while growing on inexpensive agro-industrial biomass, the competition with plant oil resources means that a significant increase in productivity is desired. The present review aims to summarize recent details in lipid metabolism research and engineering (e.g. direct fatty acid ethyl ester production), as well as culture condition optimization and innovations, such as solid-state or semi-solid-state fermentation, that can all contribute to higher productivity and further advancement of the field., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The hydrothermal reactions of calcium, strontium, and barium with l-, meso-, and d,l-tartaric acid were examined from room temperature to 220 degrees C. We report the synthesis of 13 new phases and crystal structures of 11 alkaline earth tartrates, including an unusual I(3)O(0) framework, [Ba(d,l-Tar)] (Tar = C(4)H(4)O(6)(2-)), with 3-D inorganic connectivity. Each alkaline earth exhibits different phase behavior in the reactions with the three forms of tartaric acid. Calcium forms unique l-, meso-, and d,l-tartrate phases which persist to 220 degrees C. Strontium forms three unique phases at lower temperatures, but above 180 degrees C reactions with l- and d,l-tartaric acid yield the meso phase. Likewise, Ba forms three unique low-temperature phases, but above 200 degrees C reactions with l- and meso-tartaric acid yield the d,l phase. Computational and calorimetric studies of the anhydrous calcium phases, [Ca(l-Tar)] and [Ca(meso-Tar)], strontium phases, [Sr(l-Tar)] and [Sr(meso-Tar)], and barium phases, [Ba(l-Tar)] and [Ba(d,l-Tar)], were performed to determine relative phase stabilities and elucidate the role of thermodynamic and kinetic factors in controlling phase behavior. The computational and calorimetric results were in excellent agreement. The [Ca(meso-Tar)] phase was found to be 9.1 kJ/mol more stable than the [Ca(l-Tar)] phase by computation (total electronic energies) and 2.9 +/- 1.6 kJ/mol more stable by calorimetry (enthalpies of solution). The [Sr(meso-Tar)] phase was found to be 13.4 and 8.1 +/- 1.4 kJ/mol more stable than [Sr(l-Tar)] by computation and calorimetry, respectively. Finally, the [Ba(l-Tar)] phase was found to be 6.4 and 7.0 +/- 1.0 kJ/mol more stable than the [Ba(d,l-Tar)] phase. Our results suggest that the calcium and strontium meso phases are the most thermodynamically stable phases in their systems over the temperature range studied. The phase transitions are controlled by relative thermodynamic stabilities but also by a kinetic factor, likely the barrier to isomerization/racemization of the tartaric acid, which is hypothesized to preclude phase transformations at lower temperatures. In the barium system we find the [Ba(l-Tar)] phase to be the most thermodynamically stable phase at low temperatures, while the [Ba(d,l-Tar)] phase becomes the thermodynamic product at high temperatures, due to a larger entropic contribution.

The use of bifunctional chiral catalysts, which are able to simultaneously bind and activate two reacting partners, currently represents an efficient and reliable strategy for the stereoselective preparation of valuable chiral compounds. Cinchona alkaloids such as quinine and quinidine, simple organic molecules generously provided by Nature, were the first compounds to be proposed to operate through a cooperative catalysis. To date, a full mechanistic characterization of the dual catalysis mode of cinchona alkaloids has proven a challenging objective, due to the transient, non-covalent nature of the involved catalyst-substrate interactions. Here, we propose a mechanistic rationale on how natural cinchona alkaloids act as efficient bifunctional catalysts by using a broad range of computational methods, including classical molecular dynamics, a mixed quantum mechanical/molecular mechanics (QM/MM) approach, and correlated ab-initio calculations. We also unravel the origin of enantio- and diastereoselectivity, which is due to a specific network of hydrogen bonds that stabilize the transition state of the rate-determining step. The results are validated by experimental evidence.