Input reconstruction for statistical‐based fault detection and isolation

In this work, an input reconstruction scheme for detecting and isolating sensor, actuator, and process faults is proposed. The scheme uses model‐based and statistical‐based FDI methods, which yields an improved analysis of abnormal operation conditions in chemical processes. The main advantage of the proposed approach over existing works lies in the reconstruction of system inputs and the subsequent estimation of fault signatures. This advantage is demonstrated through simulation examples and the analysis of recorded process data from a reactive batch distillation column. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Sintered silicon nitride/nano-silicon carbide materials based on preceramic polymers and ceramic powder

A flexible method is presented, which enables the fabrication of porous as well as dense Si₃N₄/nano-SiC components by using Si₃N₄ powder and a preceramic polymer (polycarbosilazane) as alternative ceramic forming binder. The SiCN polymer benefits consolidation as well as shaping of the green body and partially fills the interstices between the Si₃N₄ particles. Cross-linking of the precursor at 300 °C increases the mechanical stability of the green bodies and facilitates near net shape machining. At first, pyrolysis leads to porous ceramic bodies. Finally, subsequent gas pressure sintering results in dense Si₃N₄/nano-SiC ceramics. Due to the high ceramic yield of the polycarbosilazane binder, the shrinkage during sintering is significantly reduced from 20 to 15 lin.%. Investigations of the sintered ceramics reveal, that the microstructure of the Si₃N₄ ceramic contains approx. 6 vol.% nano-scaled SiC segregations, which are located both at the grain boundaries and as inclusions in the Si₃N₄ grains.     

RAFT-derived polymer-drug conjugates: poly(hydroxypropyl methacrylamide) (HPMA)-7-ethyl-10-hydroxycamptothecin (SN-38) conjugates

A series of well‐defined polymer–drug conjugates were prepared in order to modify the physical properties of a known cytotoxic drug, 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), the active metabolite of irinotecan (CPT‐11). Reversible addition–fragmentation chain transfer (RAFT) polymerisation was used to covalently and site‐specifically append a defined N‐(2‐hydroxypropyl)methacrylamide (HPMA) polymer to SN‐38 using a graft‐from process. These poly‐HPMA–SN‐38 conjugates displayed excellent aqueous solubility and stability, whilst retaining the cytotoxic activity of the parent SN‐38. In vitro co‐culture assays containing both cancer and noncancer cell lines demonstrated the specificity of RAFT‐derived poly‐HPMA–SN‐38 conjugates for cancerous cells. The concept of post‐optimisation modification of small‐molecule drugs through a graft‐from polymer conjugation method is introduced.     

Low-Oxidation State Indium-Catalyzed C-C Bond Formation

The development of innovative metal catalysis for selective bond formation is an important task in organic chemistry. The group 13 metal indium is appealing for catalysis because indium-based reagents are minimally toxic, selective, and tolerant toward various functional groups. Among elements in this group, the most stable oxidation state is typically +3, but in molecules with larger group 13 atoms, the chemistry of the +1 oxidation state is also important. The use of indium(III) compounds in organic synthesis has been well-established as Lewis acid catalysts including asymmetric versions thereof. In contrast, only sporadic examples of the use of indium(I) as a stoichiometric reagent have been reported: to the best of our knowledge, our investigations represent the first synthetic method that uses a catalytic amount of indium(I). Depending on the nature of the ligand or the counteranion to which it is coordinated, indium(I) can act as both a Lewis acid and a Lewis base because it has both vacant p orbitals and a lone pair of electrons. This potential ambiphilicity may offer unique reactivity and unusual selectivity in synthesis and may have significant implications for catalysis, particularly for dual catalytic processes. We envisioned that indium(I) could be employed as a metallic Lewis base catalyst to activate Lewis acidic boron-based pronucleophiles for selective bond formation with suitable electrophiles. Alternatively, indium(I) could serve as an ambiphilic catalyst that activates both reagents at a single center. In this Account, we describe the development of low-oxidation state indium catalysts for carbon-carbon bond formation between boron-based pronucleophiles and various electrophiles. We discovered that indium(I) iodide was an excellent catalyst for α-selective allylations of C(sp(2)) electrophiles such as ketones and hydrazones. Using a combination of this low-oxidation state indium compound and a chiral semicorrin ligand, we developed catalytic highly enantioselective allylation, crotylation, and α-chloroallylation reactions of hydrazones. These transformations proceeded with rare constitutional selectivities and remarkable diastereoselectivities. Furthermore, indium(I) triflate served as the most effective catalyst for allylations and propargylations of C(sp(3)) electrophiles such as O,O-acetals, N,O-aminals, and ethers, and we applied this methodology to carbohydrate chemistry. In addition, a catalyst system composed of indium(I) chloride and a chiral silver BINOL-phosphate facilitated the highly enantioselective allylation and allenylation of N,O-aminals. Overall, these discoveries demonstrate the versatility, efficiency, and sensitivity of low-oxidation state indium catalysts in organic synthesis.     

Polymerization Catalysis in Liquid Propylene: High Activities and Molecular Weights in Propylene/CO Copolymerization Reactions

Summary: The dicationic [(dppp)Pd(NCCH₃)₂](BF₄)₂ catalyst (dppp = 1,3‐bis(diphenylphosphino)propane) was applied in a liquid monomer, two phase process for the CO/propene copolymerization reaction. For the first time it was possible to synthesize propene/CO copolymers with an activity up to 7 500 g/(mol · h) and molecular weights of 500 000 g/mol. Activities up to 40 000 g/(mol · h) could be obtained with the use of the unsymmetric catalyst [(CF₃‐dppp)Pd(NCCH₃)](BF₄)₂ (CF₃‐dppp = 1‐diphenylphosphino‐3‐bis[3,5‐di(trifluormethyl)phenyl]phosphinopropane) in homogeneous liquid propene solution.

Granules found after copolymerization.     

Mechanical Activation of Tetracalcium Phosphate

It was found that prolonged high-energy ball-milling of Hilgenstokite (tetracalcium phosphate, TTCP) resulted in a decrease in both particle and crystallite size, leading to a mechanical activation of the compound. This mechanically activated material demonstrated a high reactivity such that, in contrast to highly crystalline TTCP, a setting reaction with water to nanocrystalline hydroxyapatite (HA) and Ca(OH)₂ could be achieved at 37°C. However, crystalline TTCP is practically unreactive at physiologic temperatures because of the formation of a thin HA layer on the particle surface preventing further reaction.     

Erosion behavior of EB-PVD 7YSZ coatings under corrosion/erosion regime: Effect of TBC microstructure and the CMAS chemistry

Aero-engines operating in dust-laden environments often encounter a lot of dust/sand that causes a severe problem to the TBCs by means of erosion. As the turbine entry temperatures are rising, molten sand is also a big concern to the life-time of TBCs.This paper deals with the TBC behavior under the combined influence of erosion and corrosion attack. Variations in TBC morphology, CMAS infiltration time and CMAS composition and their influence on the erosion resistance at room temperature were investigated. Two different EB-PVD 7YSZ morphologies consisting of a different porosity arrangement were tested in the erosion/corrosion regime. The more ‘Feathery’ structure has a better resistance to erosion compared to a more columnar ‘Normal’ structure, which leads to less degradation of the TBC. However, under the influence of CMAS infiltration the effect was found to be reversed. In general, CMAS-infiltrated EB-PVD TBCs exhibit a higher erosion resistance than the non-infiltrated ones.     

Comparative Assessment of Complex Stabilities of Radiocopper Chelating Agents by a Combination of Complex Challenge and in vivo Experiments

For ⁶⁴Cu radiolabeling of biomolecules to be used as in vivo positron emission tomography (PET) imaging agents, various chelators are commonly applied. It has not yet been determined which of the most potent chelators—NODA‐GA ((1,4,7‐triazacyclononane‐4,7‐diyl)diacetic acid‐1‐glutaric acid), CB‐TE2A (2,2′‐(1,4,8,11‐tetraazabicyclo[6.6.2]hexadecane‐4,11‐diyl)diacetic acid), or CB‐TE1A‐GA (1,4,8,11‐tetraazabicyclo[6.6.2]hexadecane‐4,11‐diyl‐8‐acetic acid‐1‐glutaric acid)—forms the most stable complexes resulting in PET images of highest quality. We determined the ⁶⁴Cu complex stabilities for these three chelators by a combination of complex challenge and an in vivo approach. For this purpose, bioconjugates of the chelating agents with the gastrin‐releasing peptide receptor (GRPR)‐affine peptide PESIN and an integrin α_vβ₃‐affine c(RGDfC) tetramer were synthesized and radiolabeled with ⁶⁴Cu in excellent yields and specific activities. The ⁶⁴Cu‐labeled biomolecules were evaluated for their complex stabilities in vitro by conducting a challenge experiment with the respective other chelators as challengers. The in vivo stabilities of the complexes were also determined, showing the highest stability for the ⁶⁴Cu–CB‐TE1A‐GA complex in both experimental setups. Therefore, CB‐TE1A‐GA is the most appropriate chelating agent for *Cu‐labeled radiotracers and in vivo imaging applications.     

Reinforcement of a Magnesium‐Ammonium‐Phosphate Cement with Calcium Phosphate Whiskers

Self‐setting resorbable phosphate cements are characterized by an excellent biocompatibility and bioactivity. However, poor mechanical properties restrict their application. Most studies which characterize phosphate cements mechanically focus on strength measurements. Examinations of mechanical reliability and facture toughness were hardly performed. In this study, calcium phosphate whisker‐reinforced magnesium‐ammonium‐phosphate (struvite) cements were examined at the whisker–matrix interface and the measured strength, reliability and toughness values were correlated to these observations. Moreover, the toughening mechanisms were evaluated. It was shown that whisker incorporation is not beneficial for material strength. It led to a strength decrease from 29.8 to 21.8 MPa by the incorporation of 15 vol% calcium‐deficient hydroxyapatite (CDHA) whiskers compared to the pure struvite cement. Weibull statistics and microstructural observations revealed that this is caused by the whisker–matrix interface, which acts as a flaw. In contrast with that, the reliability increases upon whisker incorporation. Furthermore, the critical stress intensity factor K_IC as well as the work‐of‐fracture γ_wof increase from 0.52 to 0.60 MPam^1/2 and from 9.5 to 12.9 J/m² by the addition of 15 vol% CDHA whiskers compared to the original struvite cement. It was shown that whisker pull‐out and crack deflection are the main mechanisms responsible for this increase.