Radio-Frequency Hexamethyldisiloxane Plasma Deposition: A Comparison of Plasma- and Deposit-Chemistry

This study reports on the effect of input power to hexamethyldisiloxane (HMDSO) plasmas. The power dependence of the plasma-phase species and of the surface chemistry (of the deposits) has been investigated. Neutral and positive molecular species were detected within the plasma using mass spectrometry (MS). Secondary ion mass spectrometry (SIMS) was used to probe the molecular structure of the deposits. The elemental composition of the surface was determined by XPS and the deposition rate was monitored using a vibrating quartz crystal microbalance. Neutral and cationic molecules of mass greater than HMDSO were detected in the plasma. Their formation through ion-molecule reactions is proposed. Changes in the relative concentration of plasma-phase species follow those seen in molecular species detected at the deposit surface. Thus, we believe that the molecular structure of the deposits can be related to the species present in the plasma. While traditionally the dominant mechanism in deposit formation is assumed to be free radical combinations, we propose other possibilities involving cations with the aim of putting forward a new perspective on plasma polymerization mechanisms and thereby stimulating discussion.     

A novel approach to thermal Analysis of Thin films

A novel instrument is described called the Thin film Analyser (TFA) which quantitatively measures changes in mechanical and rheological properties of drying films in-situ on a test panel. It is based around a simple force-sensing device, capable of carrying various probes, which can be positioned in anX-Y plane over the panel. Temperature control is achieved by means of a heating block under the sample. By imposing a thermal gradient along the block, measurements can be obtained at a series of temperatures in a single experiment. Several applications of the TFA to the drying of curable and latex-based coatings are discussed, as well as some more specialized uses. The TFA concept represents a novel approach to the thermal analysis of thin films.The authors gratefully acknowledge the design, engineering and software development work of the Instrument Group at ICI Paints, in particular John Hayton, Neil Burrows, Tony Evans and Ian Francis, who have now built three versions of the TFA.     

An amylopectin tris(phenylcarbamate) chiral stationary phase for high performance liquid chromatography

Amylopectin tris(phenylcarbamate) has been evaluated as a chiral stationary phase for HPLC; the influence on its cptical resolving capabilities of mobile phase composition and nature of the alcohol used as modifier has been studied. Separation and resolution of twelve arylalcohol racemates were examined. In most instances, the stationary phase exhibited high optical resolving capacity.     

Thermal Behavior of Urea-(D) Tartaric Acid and Urea-(DL) Tartaric Acid Crystals

The thermal behavior of two new non-linear optical (NLO) materials, urea-(D) tartaric acid (UDT) and urea-(DL) tartaric acid (UDLT) were studied by using DSC, TG and TMA. The results show that: 1) The two crystals have different melting points but similar decomposition temperatures due to the influences of intermolecular forces, which is attributed to the stereo effects of (D)-tartaric and (DL)-tartaric acid molecules; 2) There was only thermal expansion and no thermal contraction when the UDT and UDLT crystals were heated; 3) There was no phase transition within the measured temperature range; 4) The thermal expansion of the UDT and UDLT crystals shows a small anisotropy; 5) The specific heats of UDT and UDLT change linearly with temperature in the measured temperature range and the value for UDT is 1.321 J g-1 K-1 at 320 K while the specific heat of UDLT is 1.357 J g-1 K-1 at the same temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of the D-Galactopyranoside Derivative of C_(60)

ThefascinatingsbocturesandpropertiesoffullereneshaveoPeneduPanewfieldofchendstry.Inparticular,F.Wudletal.l'2haveshownthatwatersofubleC6ocomPoundsinhibittheHITVen-zymesprotease(HIVP)andreversetranscriPtase(HIVRT).IthasbeenafocusofstUdytoinvestigatethebiologicalactivitiesofthesenovelsubstances.Fortheirpossiblemedicaluses,tolinkC6omoleculetonaturalProductssuchassugars,pephdes,amioacides,andsoonisanimPortantmethodinthisfield.Vasella3reportedthefirstglucosidederivativeofC6o'InthispaPer,w…     

Study on the Photophysical Process in N-Phenyl Phenothiazine and N-(2-Pyridine) Phenothiazine

By the measurements of the solvent and temperature effects of the fluorescence emission spectra and lifetime of N-phenyl phenothiazine (PHZ) and N-(2-pyridine) phenothiazine (PYZ),the existence of strongly twisted intramolecular charge transfer (TICT) state in PYZ emission spectra is proved.The exciplex formed by PHZ, PYZ and dimethyl terephthalate (DMTP) is investigated, and moreover, the transient absorption spectra of positive and negative ions as the results of the dissociation of the exciplex in the polar solvents is observed through the flash photolysis.     

Sample preparation procedure for the determination of sulphur and trace metals in oil products by the ICP with a minitorch using emulsions

A quick sample preparation method was used for the determination of sulphur and trace metals in oil and oily products by the ICP with a minitorch. Stable aqueous emulsions of oils and oil products were made by using two kinds of emulsifiers (one with low sulphur content, the other sulfonated). Aqueous standard solutions can be used for the preparation of calibration solutions. The contents of S, Al, Cr, Cu, Fe, Mg, Ni and Pb in aqueous emulsions were determined and the results were in good agreement with the composition of oil standard solutions used for control analysis procedure.     

Pyrolysis chemical ionization mass spectrometry of cellulose ethers

Pyrolysis ammonia chemical ionization (PyCI) mass spectrometry was performed on hy-droxyethyl-, hydroxypropyl-,methyl-, hydroxypropylmethyl-, and ethylhydroxyethyl cel-luloses. The mass peaks in the PyCI mass spectra of these cellulose ethers could be assigned to the ions of pyrolytic dissociation products which form via the [2 + 2 + 2] cycloreversion and the E_i elimination pyrolysis pathway. Structural information about the residual amount of nonderivatized cellulose, the relative chain length distributions of the substituents in hydroxyalkyl celluloses, and the end-capping of hydroxyalkyl substituents by alkyl groups in the mixed cellulose ethers is obtained. Interference of secondary pyrolysis products in the PyCI mass spectra is found to be of minor importance, especially in the lower mass regions. © 1995 John Wiley & Sons, Inc.     

重金属Pb2+对玉米苗生长的影响

以水栽培的玉米幼苗为材料，用不同浓度的醋酸铅溶液处理后，分别在第10天、第20天、第30天对玉米苗的根、茎、叶分别进行Pb^2＋含量测定。分析结果：Pb^2＋在玉米体内的分布表现为根〉叶〉茎；玉米中的叶绿素含量均降低；随着Pb^2＋浓度的增大，玉米细胞的膜透性表现根〉叶〉茎依次升高；Pb^2＋对玉米的伤害率的大小表现为根〉叶〉茎。该实验为进一步研究农作物对重金属Pb^2＋的耐性和重金属Pb^2＋在农作物体内的分布提供了可参考的数据。