Wetting for self-healing and electrowetting for additive manufacturing

Advanced additive manufacturing actively widens its tool box of wettability-related phenomena to be used in production of new items. Novel self-healing engineering materials incorporate vascular networks with two types of nanochannels: the one containing a resin monomer, whereas another one — a curing agent. If such nanocomposites are damaged locally, both types of channels are locally broken, and they release resin monomer and curing agent droplets. These droplets spread by wettability over the nanotextured matrix, touch each other, and coalesce, which triggers polymerization reaction and crack stitching. Wettability-facilitated droplet spreading is accompanied by liquid imbibition in the pores in the nanofiber network. Such process peculiarities are in focus in the present review. An additional process relevant in direct writing and 3D printing is electrowetting (EW). It stems from the change in the contact angle in response to the electric polarization of dielectric substrates. EW allows movement of droplets on horizontal, vertical, and inverse surfaces, which can significantly facilitate the existing direct writing and 3D printing technologies. Accordingly, EW is also in focus in the present review.     

Supercomputing and supercomputers for science and engineering in general and for chemistry and biosciences in particular

We start by pointing out relationships between production of information, global simulation, and supercomputing, thus placing our research activities in today's society context. Then we detail the evolution in hardware and software for 1CAP, our experimental supercomputer, which we claim to be especially well suited for supercomputing in science and engineering. A preliminary discussion of 1CAP/3090 (our latest experimental effort) is included. Many examples from different disciplines are provided to verify our assertions. We “prove” our point by presenting an example of global supercomputing. Starting with 3 nuclei and 10 electrons, building up to a single water molecule, then to a few hundred, we learn, for example, about Raman, infrared, and neutron scattering; we then move up to a few hundred thousand molecules to analyze particle flow and obstructions; finally we experiment, but only preliminarily, with a few million particles to learn more on nonequilibrium dynamics as in the Rayleigh-Benard systems. In this way, quantum mechanics is overlapped with statistical mechanics and expanded into microdynamics. The entire paper is finally reanalyzed from a different perspective, presenting rather systematically, even if most briefly, our ideas on “modern” computational chemistry, where quantum mechanics is as much needed as fluid dynamics and graphics. In this section the main computational techniques are analyzed in terms of computer programs and their associated flow diagrams to solve the basic equations using parallel supercomputers.     

Indicator organisms for safety and quality--uses and methods for detection: minireview

Indicator organisms have been used for nearly a century to assess the microbiological status of water and foods. Beginning with their use in water sanitation programs, their applications have been extended over the years to other products, and they have become important components of the microbiological testing programs of both industry and regulatory agencies. Functionally, they may be viewed as safety or quality indicators. Safety indicators suggest the presence of conditions associated with increased risk of exposure to a pathogen. Quality indicators assess conditions of importance to product manufacture or consumer acceptability. This minireview summarizes the history, use, and analytical methods for the most commonly used indicator organisms, including the aerobic plate count, yeasts and molds, the coliform groups,     

Perspectives for microelectrode arrays for biosensing and membrane electroporation

Electrochemical microelectrode devices are among the great challenges for bioelectrochemistry, cell biology and recently also for biomedical research and new clinical electrotherapies. Two representative cases in cell biology and medical research for new trends in the technical devices are selected, heading at new diagnostic and therapeutic clinical applications. One example is from the field of biosensing cholinergic neurotransmitter substances by the nicotinic acetylcholine receptor (AcChoR) in solid-supported lipid bilayer membrane and the other one refers to new developments of electrode systems for the electrochemical delivery of drugs and genes to biological cell aggregates and tissue by the powerful method of membrane electroporation. In both cases addressed to, the new developments include the use of electrical feedback control of electrode arrays for biosensing processes as well as for the extent and duration of tissue electroporation. In line with the impressive advances in medical microsurgery, where increasingly smaller organ targets become accessible, microelectrode systems have become a continuous technical challenge for bioanalytical purposes and, as discussed here in some detail, for the new field of the electroporative delivery of effector substances like drugs and genes, using miniaturized electrochemical electrode arrays.     

Radionuclides used for therapy and suggestion for new candidates

Summary Targeted radiotherapy has the potential to provide radiation doses from a wide range of radionuclides, some of them suitable for killing single cells while others are more suitable for killing tumor cell clusters of various sizes. A list of 64 radionuclides, including 20 new potential candidates for therapy (⁷³Ga, ⁷⁵Se, ^87mSr, ⁹⁷Ru, ¹⁰³Ru, ¹¹³Sn, ^113mIn, ¹¹⁷Sb, ¹²³Sn, ¹³¹Cs, ¹³⁹Ce, ¹⁴¹Ce, ¹⁴⁹Eu, ¹⁶⁷Tm, ¹⁷⁰Tm, ¹⁷³Tm, ¹⁹⁵Au, ^195mPt, ¹⁹⁷Pt and ¹⁹⁷Hg) were analyzed in terms of the suitability of their energies for killing tumor cells which grow as single, small, intermediate and large clusters. In addition, their possible production routes were studied.     

A high-frequency apparatus for chromatographic recording and for titration

Summary A high-frequency device, using the Q-meter principle, has been tested. It is compared with a simple crystal oscillator. It was found that the stability is increased about 100 times. The new device can find application in chromatographic recording and for monitoring purposes. A titration cell with a defined cell-constant is also described.

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Zusammenfassung Ein Hochfrequenzgerät nach dem Q-Meter-Prinzip wurde getestet und mit einem einfachen Kristalloszillator verglichen. Die Stabilität des ersteren ist etwa 100fach größer. Das neue Gerät kann zur chromatographischen Registrierung und für Zwecke der Betriebsüberwachung verwendet werden. Eine Titrationszelle mit definierter Zellkonstante wurde gleichfalls beschrieben.

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Résumé On a mis à l'essai un dispositif haute-fréquence mettant en application le principe du compteur-Q. On le compare avec un oscillateur simple à cristal. On a trouvé que la stabilité est augmentée d'environ cent fois. Le nouveau dispositif peut trouver une application dans l'enregistrement chromatographique et pour des usages de contrôle. On décrit également une cuve de titrage avec une constante de cellule définie.

     

Guidelines for CITAC projects and CITAC procedure for support of conferences and workshops

News and Announcements

Guidelines for CITAC projects and CITAC procedure for support of conferences and workshops     

A procedure for sampling and analysis of air for energetics and related compounds

A procedure for the sampling and analysis of energetics and related compounds in the atmosphere is described. The basic procedure consists of the collection of air samples using sampling cartridges containing XAD-2 resin, extraction of the resin with isoamyl acetate, and an analysis of the extract using gas chromatography with electron capture detection. Modifications and additions to this procedure are discussed, such as the use of a prefilter before the resin sampler to collect particulates and the use of a mass selective detector to analyze for some propellant compounds of interest or for quantitative confirmation purposes. Two differing sizes of samplers are evaluated according to the air volumes required for collection. The procedure is tested through the analysis of spiked resin samples, which had air pulled through them for periods of time corresponding with the required sampling volumes. This procedure has application toward the measurement of energetic residues in atmospheres resulting from weapons testing and operations during training exercises involving munitions.     

Possibilities for separation and simultaneous determination of N-unsubstituted- and N-substituted nitroimidazoles and criteria for their identification

The N-unsubstituted nitroimidazoles have an imino hydrogen atom in contrast to the N-substituted derivatives, and react with hydroxide to give the yellow nitroimidazole anions. The difficulty of reducing the nitro-group in these anions, together with the shift of the absorption maximum to longer wavelengths makes it possible to analyse polarographically or spectrophotometrically a mixture of N-unsubstituted nitroimidazole with N-substituted derivatives. The presence of the N-unsubstituted nitroimidazole and the N-substituted derivatives is first established by chromatography. Other criteria are also proposed for distinguishing between these substances.     

Expressions for the stress and elasticity tensors for angle-dependent potentials

The stress and elasticity tensors for interatomic potentials that depend explicitly on bond bending and dihedral angles are derived by taking strain derivatives of the free energy. The resulting expressions can be used in Monte Carlo and molecular dynamics simulations in the canonical and microcanonical ensembles. These expressions are particularly useful at low temperatures where it is difficult to obtain results using the fluctuation formula of Parrinello and Rahman [J. Chem. Phys. 76, 2662 (1982)]. Local elastic constants within heterogeneous and composite materials can also be calculated as a function of temperature using this method. As an example, the stress and elasticity tensors are derived for the second-generation reactive empirical bond-order potential. This potential energy function was used because it has been used extensively in computer simulations of hydrocarbon materials, including carbon nanotubes, and because it is one of the few potential energy functions that can model chemical reactions. To validate the accuracy of the derived expressions, the elastic constants for diamond and graphite and the Young's Modulus of a (10,10) single-wall carbon nanotube are all calculated at T = 0 K using this potential and compared with previously published data and results obtained using other potentials.     

Handling techniques for submicrogram samples for X-ray diffraction and analyses

Summary A relatively simple method of mounting microgram and submicrogram specimens for X-ray diffraction is described. The method involves the use of plastic spikes with oils as adhesives. These adhesives permit the use of the same specimen for determination of refractive index, spectrographic analyses, etc.

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Zusammenfassung Ein verhältnismäßig einfaches Verfahren zum Montieren kleiner Teilchen für Röntgenstudien wird beschrieben. Teilchen von 0,05g bis mehrere Mikrogramm werden mit trocknendem Öl an Plastikspießen befestigt, so daß sie für die Bestimmung des Brechungsvermögens, für die spektrographische Analyse oder andere Untersuchungen wieder abgelöst werden können.

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Résumé On décrit une méthode relativement simple pour le montage d'échantillons de l'ordre du microgramme et du submicrogramme sur les appareils à diffraction de rayons X. La méthode utilise des pointes en matière plastique et des huiles comme adhésifs. Ces adhésifs permettent l'emploi du même échantillon pour la détermination de l'indice de réfraction, les analyses spectrographiques, etc.

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4400 W. 45th Street, Chicago 32, Ill.     

Keto-coumarin scaffold for photoinitiators for 3D printing and photocomposites

The purposes of this paper are moving toward (a) the development of a new series of photoinitiators (PIs) which are based on the keto-coumarin (KC) core, (b) the introduction of light-emitting diodes (LEDs) as inexpensive and safe sources of irradiation, (c) the study of the photochemical mechanisms through which the new PIs react using different techniques such as Fourier transform infrared, UV–visible or fluorescence spectroscopy, and so on, (d) the use of such compounds (presenting good reactivity and excellent photopolymerization initiating abilities) for two specific and high added value applications: 3D printing (@405 nm) and preparation of thick glass fiber photocomposites with excellent depth of cure, and finally (e) the comparison of the performance of these KC derivatives versus other synthesized coumarin derivatives. In this study, six well-designed KC derivatives ( KC-C , KC-D , KC-E , KC-F , KC-G , and KC-H ) are examined as high-performance visible-light PIs for the cationic polymerization of epoxides as well as the free-radical polymerization of acrylates upon irradiation with LED@405 nm. Excellent polymerization rates are obtained using two different approaches: a photo-oxidation process in combination with an iodonium (Iod) salt and a photo-reduction process when associated with an amine (N-phenylglycine or ethyl 4-(dimethylamino)benzoate). High final reactive conversions were obtained. A full picture of the involved photochemical mechanisms is provided.     

Photocaging strategy for functionalisation of oligonucleotides and its applications for oligonucleotide labelling and cyclisation

We have used a photocaging strategy to develop novel phosphoramidites and expand the repertoire of protecting groups for modification of oligonucleotides by solid-phase synthesis. We synthesised five photolabile phosphoramidites and four new photolabile controlled pore glasses (CPGs). By using these photolabile phosphoramidites and CPGs, modified oligodeoxynucleotides (ODNs) with phosphate, amine, acid, thiol and carbonyl moieties at 5' and/or 3' ends were readily synthesised. To the best of our knowledge, this is the first report of introducing a carbonyl at the 5' end and thiol groups at both ends of ODNs with photolabile modifiers. Terminal labelling was also easily realised in solution or by on-column solid-phase synthesis. By using the photolabile amine modifier and the photolabile acid CPG, cyclisation of an oligodeoxynucleotide was achieved with good yields. This study provides an alternative way to introduce functional groups into oligonucleotides and expand the scope of oligonucleotide bio-orthogonal labelling.     

Molecularly imprinted polymers for bisphenol A for HPLC and SPE from water and milk

Molecularly imprinted polymers (MIPs) for bisphenol A (BPA) were prepared by two synthetic routes: semi-covalent and noncovalent methodology. The molecular imprinting effect was evaluated using the polymers in HPLC and SPE. Polymers prepared with noncovalent mode were proven more effective. These polymers were applied in SPE facilitating selective retention of BPA from bottled water and milk. The developed sample preparation was simple and efficient comprising only dilution of milk and MISPE prior to LC-MS analysis. Overall MISPE enhanced sample clean-up. Compared with control nonimprinted polymers and conventional C18 SPE cartridges, the MIPs exhibited selective analyte recognition. The method provided quantitative BPA recoveries, very good reproducibility (% RSDs lower than 7%), and low LOD (0.2 ng/g). MIP interacts similarly with deuterated BPA allowing its use as internal standard in LC-MS. The most critical parameters of MISPE were the organic content in loading-washing medium and the washing volume. Low flow rates in the elution step enhanced extraction recovery. Important advantages of the MIP were: the high breakthrough volumes (> 500 mL of water), high mass capacity (> 10 ng/mg of MIP sorbent), good linearity, and good stability in performance for over 35 cycles of use.     

Rapid potentiometric methods for vanadium and for analysis of ferrovanadium and some vanadium steels

Rapid and reliable potentiometric methods are given for determination of vanadium based on titrating unreacted KBr or KI in H₂SO₄ acid medium with Hg(I) or Hg(II), using silver amalgam as the indicator electrode. The methods are successfully applied to the analysis of ferrovanadium, three varieties of vanadium steels and synthetic mixtures of about identical constitution. In all cases the potential breaks were sharp enough for the accurate determination of the end points.     

高校化学类专业课程思政建设目标与实现途径刍议——以物理化学课程教学为例

课程思政建设是当前专业课程教学改革的重要内容。课程思政建设应以专业人才培养目标为指引,基于"以学生为中心""以产出为导向"的理念进行系统设计和实施。本文以物理化学课程教学为例,介绍如何围绕课程教学目标,对课程思政进行系统设计,深入挖掘课程育人功能,突出世界观和方法论教学,突出学生综合评价能力、学科思维能力和批判创新能力的培养,推动专业教学由知识导向型向能力和素质导向型转变。