Types Of CF Research Articles

Simple organofluorine compounds giving field-dependent 13 C and 19 F NMR spectra with complex patterns: higher order effects and cross-correlated relaxation

The CF(3) signals in the (13)C{(1)H} spectrum of 1,1,1,3,3,3-hexafluoroisopropyl alcohol and the (CF(3))(2) CH signals in the corresponding triflate exhibit much greater complexity than might first be expected. The same holds for the (13)C satellites in the (19)F spectra. Complex patterns appear because of higher order effects resulting from the combination of a relatively large four-bond (19)F-(19)F J coupling in the ((13)CF(3))(12)CH((12)CF(3))-containing isotopomer and a typical large one-bond (13)C/(12)C isotope effect on the (19)F chemical shift. This complexity cannot be eliminated at very high magnetic field strengths. The triflate (CF(3))(2)CH-O-SO(2)CF(3) presents still additional complexity because of the presence of two different types of CF(3) groups exhibiting (6)J(FF) in any of the isotopomers and the chemical shift differences in hertz between the various (19)F signals in the two different (13)CF(3)-containing isotopomers. In addition, the presence of a small (5)J(CF) in the ((13)CF(3))((12)CF(3))(12)CH-O-SO(2) (12)CF(3) isotopomer is revealed only through simulations. The hexafluoroisopropyl CF(3) groups in the alcohol and triflate and the SO(2)CF(3) group in the triflate apparently provide the first examples of cross-correlated relaxation in (13)CF(3) groups. An analysis of the spectra in the context of previously reported work highlights the novel aspects of our findings. In particular, for each part of the complex hexafluoroisopropyl CF(3) quartet, peak height and linewidth variations resulting from cross-correlated relaxation are observed. These variations within a group of (13)C signals reflect different spin-lattice and spin-spin relaxation rates for the transitions within that group arising from higher order coupling effects.

Development of an ultraslim spindle motor for a 3.3-mm-height CF type I disk drive

This paper presents the development of an ultra-slim spindle motor for a 3.3 mm-height CF Type I disk drive. The mechanical structure of the developed motor is extremely reduced not only by eliminating the unnecessary space but also by optimizing hub and clamp in order to fit in the small form factor. Electrically, it has additional auxiliary windings in the linking part between the adjacent teeth of slotted stator, which increases the torque constant and efficiency. Simulation and experiments are performed to prove the advantages of the developed motor.

Formula omitted] NMR characterization of electron beam irradiated vinylidene fluoride–trifluoroethylene copolymers

Electron beam irradiated poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] copolymers have been recently shown to exhibit “giant” electrostrictive stains. In this work, 19 F nuclear magnetic resonance (NMR) spectroscopy was used to probe structure of P(VDF–TrFE) copolymers before and after irradiation in order to elucidate the chemistry associated with the development of outstanding electroactive properties. The two-dimensional solution-state 19 F NMR of as-synthesized copolymers reveals strong (∼300 Hz) geminal indirect coupling ( 2J ) and the resulting assignments have some differences from the previous literature. The most frequently occurring sequence containing TrFE is CH 2CF 2CHFCF 2CH 2, followed by CF 2CH 2CHFCF 2CF 2. This reveals a strong preference for the TrFE units to be isolated and a slight preference for the head-to-tail addition. Both sequences contain VDF polymerized in the same direction around the central TrFE monomer unit. Resolution of bonding environments in the insoluble irradiated P(VDF–TrFE) required the use of fast (25 kHz) magic angle spinning (MAS) solid-state 19 F NMR at elevated temperature. Of the resolved peaks formed by irradiation, the side group CF 3CH<, was present in the highest concentration. Such CF 3 pendant groups are likely to reduce crystallinity and thus impact electroactive properties. Also observed was significant formation of CF 3CF 2, which can be either a pendant group or a side group. Several types of CF 3 end groups were observed: CF 3CHF, CF 3CH 2, and CF 3CH. The latter, indicates the formation of some unsaturated bonds upon irradiation. Small concentrations of CHF 2 and CF 2H were also found. Cross-linking is indirectly evidenced by broadening of the NMR spectra of the irradiated material. In the unirradiated copolymer, two conformation; of sequence CH 2CF 2CHFCF 2CH 2 are observed in the solid-state. In the solution-state in the post-irradiated solid-state, only one of these conformations exists.

ＳＥＭ内クリープ疲労試験による微視的損傷過程の連続観察

Creep-fatigue damage occurs gradually in high temperature components and structures. It is necessary to clarify the micro-damage evolution mechanism under creep-fatigue conditions for the quantitative evaluation of creep-fatigue damage in local portions of the components. In order to examine the relation between damage evolution and change of microstructure, such as creep cavities and surface microcracks, strain controlled creep-fatigue tests were performed and interrupted at several damage levels. The creep-fatigue tests were also performed under a low stress level by the high temperature fatigue machine combined with a scanning electron microscope (SEM), and the microcrack initiation and growth behavior were continuously observed by the SEM during the tests.It was found that even though many cavities were initiated and grew at the internal grain boundaries of the specimens during the strain controlled creep-fatigue tests, the failure life was governed by the propagation of surface cracks. On the other hand, microcracks of about one grain size order initiated mainly on the grain boundaries normal to the loading axis under low stress creep-fatigue, and the crack propagation rate of the microcracks was slow and at random by the influence of microstructure. The microcracks gradually opened to the loading direction with increasing number of cycles and coalescening occurred to grow. From the experiments, the creep-fatigue damage extension mechanism was divided into the Fc type, where the main cracks on the surface propagated through damaged grain boundaries, and Cf type, where damage evolution was characterized by opening and coalescening of the microcracks.

Structure of the ATP synthase from chloroplasts studied by electron microscopy. Localization of the small subunits

The structure of the hydrophilic part of the ATP synthase from chloroplasts (CF 1) has been further investigated by electron microscopy and image analysis of negatively stained samples. The projections of three different types of CF 1 were analyzed: the holoenzyme with five different subunits and two CF 1 particles depleted of δ and of δ,ϵ, respectively. About 1000 images of molecular projections of each of the three types were analyzed. They were aligned relative to different reference images and were then submitted to a multivariate statistical classification procedure. The analysis has been focussed on the projections of the hexagonal type. Comparisons between the average images of the three types of CF 1 and between the previously analyzed CF 1- and mitochondrial MF 1 ATP synthases clearly outline the many detailed similarities but also the differences. Removal of δ leads to a significant decrease in the diameter of CF 1: the distances between opposive large α and β subunits decrease by 1.3 nm. The additional removal of ϵ has no further effect on these distances. The positions of the small subunits could be localized within the α 3 β 3 structure. Subunit γ is located in the center of the hexagonal projection and has dimensions of 2.5–2.8 nm in the plane and about 5 nm in the vertical direction. Subunits δ and ϵ are located between γ and one pair of large α and β subunits, resulting in the V-shaped central mass, as found previously. The position of δ or ϵ is perhaps variable, since among the previously analyzed 3300 CF 1 projections, many projections were found with the central mass divided in two parts, with the smallest mass in different positions. Consequences of these findings for the mechanism of ATP synthesis are discussed.

極低繰返し速度下におけるＨＴ８０とＳＵＳ３０４鋼の腐食疲労き裂伝ぱの加速現象

Fatigue crack growth properties under freely corroding and cathodic protection in 3%NaCl aqueous solution were studied under very-low cycling for HT80 high tensile and SUS304 stainless steels. The crack growth rate in 3%NaCl solution was accelerated as compared with that in air. The acceleration was dependent on material, environment, ΔK-level and frequency, and the following three types of acceleration was observed.(1) The CF type acceleration was inherent to corrosion fatigue in free corroding and the rate was accelerated about twice at frequencies lower than 0.3Hz independently of material and ΔK level.(2) The HE(IG) type was related to the intergranular cracking due to hydrogen embrittlement and appeared in the range of ΔK from 4 to 20MPa·m1/2 and at frequencies from 10-3 to 102Hz only for HT80 steel. The maximum acceleration rate became about five times at ΔK=10MPa·m1/2 and f=0.3Hz.(3) The HE(TG) type was related to the transgranular and brittle fracture due to hydrogen embrittlement and the rate became constant at frequencies lower than 0.03Hz. This type was also dependent on material, environment and ΔK level. The maximum acceleration rate was nearly thirty and ten times for TH80 and SUS304 steels, respectively.

高温高圧純水におけるＳＵＳ３０４鋼の応力腐食割れ 溶体化処理温度および鋭敏化処理の影響

Effects of solution temperature and sensitization time on the stress corrosion cracking (SCC) cf type 304 stainless steel were studied in high temperature water at 562 K containing dissolved oxygen of 8 ppm, using the slow strain rate testing (SSRT) technique at the strain rate of 4.17×10-6 s-1.For the specimen solution-treated at 1373 K, the SCC drastically occured by the sensitization treatment at 923 K for 7.2 ks. but the SCC hardly occurs even at 100 ks of sensitization time for the specimens solution-treated at 1473 K and 1573 K.For the specimen solution-treated at 1373 K, the size of grain boundary carbides and the width of attacked grain boundaries after sensitization treatment of 7.2 ks, are larger than the size and width solutiontreated at 1473 K and 1573 K according to transmission electron microscopy and Strauss test. The corrosion rates of grain boundary attack on Huey test increased with the holding time in solution treatment at 1373 K for both the solution-treated specimen and the sensitized specimen after solution-treated.The results suggest that impurity elements segregate to the grain boundaries during solution treatment at 1373 K, and accelerate the precipitation of grain boundary carbides during sensitization.The SCC occurs under the presence of both the Cr depleted zone by the sensitization and impurity elements at grain boundary.

圧痕の形成要因およびその抑制方法 ＩＩＩ 高電流密度・短時間通電方式スポット溶接の研究

In the spot welding process using high-current density (nearly 2.0 kA/mm2) and short current duration (4.0 ms ), the indentation on sheet is smaller than one in the conventional spot welding process (heat conduction type). But, in case of welding using R type or CF type electrode tips, its indentation is clear in visual inspection at welds showing the tear rupture at the tensile shear testing.In this report, it is cleared that the indentation is formed mainly by following three factors; the softening in sheet surface caused by heating by the contact resistance between electrode and sheet, the current concentration in the electrode edge, and electrode force.Furthermore, it is shown experimentally that the joint of thin steel sheets or Al alloy plates with enough tensile shear strength and extremely small indentation (about 0.01 mm) are obtained easily by using the combination of R type and F type electrodes.

Compound action potentials and single unit responses to a 1 kHz haversine in the cat

The single-cycle 1 kHz haversine (one cycle of a 1 kHz sine wave beginning at −90° ) is a low-frequency impulsive stimulus which has been little used, but which has significant potential applications both as a clinical and a research tool. The auditory nerve compound action potential (CAP) and single unit discharge patterns evoked by a single-cycle 1 kHz haversine stimulus were studied in anesthetized cats. The haversine CAP waveform consisted of two or three short latency peaks with peak to peak intervals of about 1.0 ms. Latencies of the CAP peaks decreased with increased stimulus intensity and were also strongly dependent on stimulus polarity. Typically, CAP peak latencies changed by about 0.5 ms with stimulus polarity reversal. Single unit responses were classified by the peak latency pattern of their haversine post-stimulus time histograms (PSTHs). Low CF units had low thresholds and PSTHs resembling their click responses. High CF units had high thresholds and PSTHs comprised of one or two short latency peaks whose latencies were polarity-sensitive. Some units in an intermediate CF range (approximately 1.5–3.0 kHz) had PSTHs which were a transitional form between the high and low CF types of response. The unit discharge patterns strongly suggested a low frequency origin for the haversine CAP at all intensities.

A variable temperature study of the 19-F N.M.R. spectrum of perfluorohexamethyltetrazan: Novel restricted rotation and hindered inversion at the nitrogen atoms [1

At low temperatures, the 19F n.m.r. spectrum of the tetrazan (CF 3) 2NN(CF 3)N(CF 3)N(CF 3) 2 shows the presence of two isomers with a free energy difference in stability Δ G of 2.2 kJ mol -1. Both isomers show three types of CF 3 group which coalesce at -15°C to three systems of equal intensity (Δ G ≠ 52 kJ mol -1). At 40 °C the two signals assigned to the terminal CF 3 groups coalesce to a single band (Δ G ≠ 65 kJ mol -1). The behaviour is discussed in terms of restricted inversion at the nitrogen atoms, and hindered rotation about the N-N bonds. The hydrazines (CF 3) 2NN(CF 3)NO and (CF 3) 2NN(CF 3)NO 2 have temperature independent spectra.

An Electron Probe Microanalyzer Investigation on Phase Reactions during Firing of Iron Ore Pellets

AbstractProcesses during the firing of pellets consisting of siderite concentrate and Ca(OH)2 have been studied by means of X‐ray diffractometer and microanalyzer. When temperature is higher than 400°C thermal siderite decomposition starts, producing haematite and calcite being observed up to 600°C with the technique of oscillating X‐ray detector. With increasing temperature CaO which arises from calcite doesn't react with SiO2 up to 750°C; Fe2O3 grains grow. Above 1000°C CaO is dissolved in Fe oxides, and ferrite of CF type is formed. At temperatures higher than 1130°C a new phase is forming, presumedly a ferrite CF2. Results of the study of this phase being stable up to 1250°C are reported.

The influence of the indifferent electrode upon the precordial electrocardiogram: I. The normal electrocardiogram

1. 1. Standard limb leads, unipolar limb leads (extremity potentials), unipolar precordial leads, and precordial leads of the CR, CL, and CF types were taken in a series of normal subjects. Analysis of the curves thus obtained justifies the following conclusions: 2. 2. The position of the reference electrode has a considerable effect upon the size and form of the normal precordial electrocardiogram. 3. 3. The potential variations of the left arm in CL leads and the influence of the potential variation of the left leg in CF leads vary with the position of the mean electrical axis of P, QRS, and T. The distortion which occurs in CR leads is not appreciably less than that in CL and CF leads, but is much more uniform in magnitude and in duration when the electrical axes of P, QRS, and T are in a relativel normal position. 4. 4. When a central terminal is employed, the distortion introduced by the reference electrode is eliminated or reduced to a minimum.