Active vibration suppression of smart beams

In this paper an active vibration control technique for a smart beam is presented. The structure is made of two layers of piezoelectric material (PZT8) embedded on the surface of an aluminium beam. The active control is inserted into the finite element model by using programming tools of the general purpose code used here. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and polymerization of amphiphilic methacrylates containing permanent dipole azobenzene chromophores

New amphiphilic photochromic methacrylates with the structures of 4‐[ω‐methacryloyloxyoligo(ethyleneglycol)]‐4′‐cyanoazobenzene (MEn) and 4‐methacryloyloxy‐4′‐{2‐cyano‐3‐oxy‐3‐[ω‐methoxyoligo(ethyleneglycol)]prop‐1‐en‐1‐yl}azobenzene (MEnMe) and oligo(oxyethylene) segments of different lengths were synthesized. These methacrylates were characterized by the presence of permanent dipole azobenzene chromophores and hydrophilic oligo (oxyethylene) segments. The methacrylates were obtained with six‐step and five‐step synthetic sequences, respectively, in 12–47% overall yields. The radical polymerization of the MEn monomers afforded a 50% yield of the corresponding polymers as orange solids with a number‐average molecular weight of about 40 kD. No solid polymer was obtained from the radical polymerization of the MEnME compounds. Two‐dimensional NMR spectra allowed the unequivocal assignment of the NMR signals and demonstrated a significant contribution of internal charge transfer to the electronic distribution of the azobenzene chromophore. Relaxation time measurements confirmed that the flexible polyether segment effectively decoupled photochromic groups from the polymer backbone. Optical microscopy, differential scanning calorimetry analysis, and X‐ray diffraction data demonstrated the presence of interdigitated smectic mesophases. The stability of mesophases showed a significant dependence on the chemical structure of the analyzed compounds. The glass‐transition temperatures of the polymers were rather low because of the plasticizing effect of the spacers. The monomers and polymers were used for the deposition of Langmuir films and Langmuir–Blodgett–Kuhn multilayers. A strong influence of the macromolecular structure on the film properties was observed. The photoresponsive properties of monomers and polymers were investigated with irradiation at different wavelengths. Isomerization kinetics were independent of both molecular weight and spacer length. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2957–2977, 2001     

Establishing the selective phospholipid membrane coordination,permeation and lysis properties for a series of ‘druggable’ supramolecular self-associating antimicrobial amphiphiles

The rise of antimicrobial resistance remains one of the greatest global health threats facing humanity. Furthermore, the development of novel antibiotics has all but ground to a halt due to a collision of intersectional pressures. Herein we determine the antimicrobial efficacy for 14 structurally related supramolecular self-associating amphiphiles against clinically relevant Gram-positive methicillin resistant Staphylococcus aureus and Gram-negative Escherichia coli. We establish the ability of these agents to selectively target phospholipid membranes of differing compositions, through a combination of computational host:guest complex formation simulations, synthetic vesicle lysis, adhesion and membrane fluidity experiments, alongside our novel ¹H NMR CPMG nanodisc coordination assays, to verify a potential mode of action for this class of compounds and enable the production of evermore effective next-generation antimicrobial agents. Finally, we select a 7-compound subset, showing two lead compounds to exhibit ‘druggable’ profiles through completion of a variety of in vivo and in vitro DMPK studies.

A combination of computational and synthetic phospholipid vesicle/nanodisc assays are used to investigate the mode of action for a class of antimicrobial agents, while a range of DMPK studies establish agent druggability.     

Certification of standard reference material (SRM) 1941a, organics in marine sediment

SRM 1941a, Organics in Marine Sediment, has been recently issued with certified concentrations for 23 polycyclic aromatic hydrocarbons, 21 polychlorinated biphenyl congeners, 6 chlorinated pesticides, and sulfur. Noncertified concentrations have been also reported for additional PAHs, PCB congeners, and chlorinated pesticides and for percent total organic carbon (TOC), aliphatic hydrocarbons, and trace elements. SRM 1941a is the most extensively characterized natural matrix SRM issued by the National Institute of Standards and Technology (NIST).     

Role of the direct reaction H2S + SO2 in the homogeneous Claus reaction

Quantum chemical methods at the Gaussian-2 and -3 levels of theory have been used to investigate the reactions between H(2)S, SO(2), and S(2)O such as might occur in the front-end furnace of the Claus process. The direct reaction between H(2)S and SO(2) occurs via a 5-centered transition state with an initial barrier of approximately 135 kJ mol(-1) and an overall barrier of approximately 153 kJ mol(-1) to produce S(2)O and H(2)O. We indicate approximate values here because there are a number of isomers in the reaction pathway that have barriers slightly different from those quoted. The presence of a water molecule lowers this by approximately 60 kJ mol(-1), but the van der Waals complex required for catalysis by water is thermodynamically unfavorable under the conditions in the Claus reactor. The direct reaction between H(2)S and S(2)O can occur via two possible pathways; the analogous reaction to H(2)S + SO(2) has an initial barrier of approximately 117 kJ mol(-1) and an overall barrier of approximately 126 kJ mol(-1) producing S(3) and H(2)O, and a pathway with a 6-centred transition state has a barrier of approximately 111 kJ mol(-1), producing HSSSOH. Rate constants, including a QRRK analysis of intermediate stabilization, are reported for the kinetic scheme proposed here.     

The Onset of Dehydrogenation in Solid Ammonia Borane: An Ab Initio Metadynamics Study

The discovery of effective hydrogen storage materials is fundamental for the progress of a clean energy economy. Ammonia borane (H₃BNH₃, AB) has attracted great interest as a promising candidate but the reaction path that leads from its solid phase to hydrogen release is not yet fully understood. To address the need for insights in the atomistic details of such a complex solid state process, in this work we use ab‐initio molecular dynamics and metadynamics to study the early stages of AB dehydrogenation. We show that the formation of ammonia diborane (H₃NBH₂(μ‐H)BH₃) leads to the release of NH₄⁺, which in turn triggers an autocatalytic H₂ production cycle. Our calculations provide a model for how complex solid state reactions can be theoretically investigated and rely upon the presence of multiple ammonia borane molecules, as substantiated by standard quantum‐mechanical simulations on a cluster.     

Evaluation of Detector Position and Light Fluence Distribution Using an Infrared Navigation System during Pleural Photodynamic Therapy†

Photodynamic therapy (PDT) has been used to treat malignant pleural mesothelioma. Current practice involves delivering light to a prescribed light fluence with a point source, monitored by eight isotropic detectors inside the pleural cavity. An infrared (IR) navigation system was used to track the location of the point source throughout the treatment. The recorded data were used to reconstruct the pleural cavity and calculate the light fluence to the whole cavity. An automatic algorithm was developed recently to calculate the detector positions based on recorded data within an hour. This algorithm was applied to patient case studies and the calculated results were compared to the measured positions, with an average difference of 2.5 cm. Calculated light fluence at calculated positions were compared to measured values. The differences between the calculated and measured light fluence were within 14% for all cases, with a fixed scattering constant and a dual correction method. Fluence-surface histogram (FSH) was calculated for photofrin-mediated PDT to be able to cover 80% of pleural surface area to 50 J cm⁻²(83.3% of 60 J cm⁻²). The study demonstrates that it will be possible to eliminate the manual measurement of the detector positions, reducing the patient's time under anesthesia.     

Thermal desorption direct analysis in real-time high-resolution mass spectrometry and machine learning allow the rapid authentication of ground black pepper and dried oregano: A proof-of-concept study

Thermal desorption direct analysis in real-time high-resolution mass spectrometry (TD-DART-HRMS) approaches have gained popularity for fast screening of a variety of samples. With rapid volatilization of the sample at increasing temperatures outside the mass spectrometer, this technique can provide a direct readout of the sample content with no sample preparation. In this study, TD-DART-HRMS's utility for establishing spice authenticity was examined. To this aim, we directly analyzed authentic (typical) and adulterated (atypical) samples of ground black pepper and dried oregano in positive and negative ion modes. We analyzed a set of authentic ground black pepper samples (n = 14) originating from Brazil, Sri Lanka, Madagascar, Ecuador, Vietnam, Costa Rica, Indonesia, Cambodia, and adulterated samples (n = 25) consisting of mixtures of ground black pepper with this spice's nonfunctional by-products (pinheads or spent) or with different exogenous materials (olive kernel, green lentils, black mustard seeds, red beans, gypsum plaster, garlic, papaya seeds, chili, green aniseed, or coriander seeds). TD-DART-HRMS facilitated the capture of informative fingerprinting of authentic dried oregano (n = 12) originating from Albania, Turkey, and Italy and those spiked (n = 12) with increasing percentages of olive leaves, sumac, strawberry tree leaves, myrtle, and rock rose. A predictive LASSO classifier was built, after merging by low-level data fusion, the positive and negative datasets for ground black pepper. Fusing multimodal data allowed retrieval of more comprehensive information from both datasets. The resultant classifier achieved on the withheld test set accuracy, sensitivity, and specificity of 100%, 75%, and 90%, respectively. On the contrary, the sole TD-(+)DART-HRMS spectra of the oregano samples allowed construction of a LASSO classifier that predicted the adulteration of the oregano with excellent statistical indicators. This classifier achieved, on the withheld test set, 100% each for accuracy, sensitivity, and specificity.     

Crystal and Molecular Structure of the [6-Deoxy-6-[(2-(4-imidazolyl)ethyl)amino]- cyclomaltoheptaose]copper(II) Ternary Complex with L-Tryptophanate. Role of Weak Forces in the Chiral Recognition Process Assisted by a Metallocyclodextrin

The ternary copper(II) complex of 6-deoxy-6-[(2-(4-imidazolyl)ethyl)amino]cyclomaltoheptaose (CDhm) and L-tryptophanate (L-TrpO(-)) was characterized by ESR and X-ray diffraction. The solid state structure of [Cu(CDhm)(L-TrpO)](+) shows that the aromatic side chain of TrpO(-) is outside the cavity and that the two amino nitrogen atoms, one from the histamine molecule and one from the amino acidate, are in a cis disposition. The two amino nitrogens, the imidazole nitrogen, and the carboxylate oxygen atoms form the base of a square pyramid, which surrounds the copper(II) ion, a water molecule occupying an apical position. Atomic distances suggest for this complex that pi-pi and d-pi interactions could occur in the solid state. Morover, the [Cu(CDhm)(L-TrpO)](+) has a self-assembled structure in which a CDhm molecule behaves as host and as guest. The imidazole and the indole ring are directed into the cavity of an adjacent CDhm molecule from the wider cyclodextrin rim, thus forming a polymeric column structure. ESR spectra were run on the copper(II) ternary complexes with L- or D-tryptophanate and L- or D-alaninate in frozen aqueous solution and on the former pair of enantiomers in the solid state, as well. While in the case of the ternary complex with L- or D-alaninate no differences are observed in their frozen solution spectra, in the case of complexes with TrpO(-) subtle differences are found. These differences, which disappear when excess methanol is used, are ascribed to the presence of weak forces, such as hydrophobic or d-pi interactions.     

Access to β‐Lactams by Enantioselective Palladium(0)‐Catalyzed C(sp3)H Alkylation

β‐Lactams are very important structural motifs because of their broad biological activities as well as their propensity to engage in ring‐opening reactions. Transition‐metal‐catalyzed C? H functionalizations have emerged as strategy enabling yet uncommon highly efficient disconnections. In contrast to the significant progress of Pd⁰‐catalyzed C? H functionalization for aryl–aryl couplings, related reactions involving the formation of saturated C(sp³)? C(sp³) bonds are elusive. Reported here is an asymmetric C? H functionalization approach to β‐lactams using readily accessible chloroacetamide substrates. Important aspects of this transformation are challenging C(sp³)? C(sp³) and strain‐building reductive eliminations to for the four‐membered ring. In general, the β‐lactams are formed in excellent yields and enantioselectivities using a bulky taddol phosphoramidite ligand in combination with adamantyl carboxylic acid as cocatalyst.