Unknown Carrier Research Articles

Static Probe for Electrostatic Field Measurement in the Presence of Space Charge

The conduction current to a probe incorporated into an electrode is proportional to the strength of the charge-carrier drift field; this current is modulated by a bias voltage applied betwen the probe and the electrode. The current/bias-voltage probe characteristics are described which have been derived from computation of the bias field distribution. From these design data the probe can be used to determine the strength of an unknown carrier drift field; an inherent self-verification capability is a feature of the technique. Examples of applications to direct-current point-plane corona are given.

Induction of microsomal N-hydroxylation of N-2-fluorenylacetamide in rat liver

Single or multiple injections of N-2-fluorenyl-acetamide (2-FAA) to Sprague-Dawley rats increased N-hydroxylation of 2-FAA by hepatic microsomes 3- to 12-fold without changing the content of microsomal hemoprotein (cytochrome P-450 or P 1-450) measured either by carbon monoxide difference spectra, by gel electrophoresis of microsomal preparations or by formation of the ethyl isocyanide cytochrome P 1-450 complex. Carbon monoxide inhibited N-hydroxylation of 2-FAA by hepatic microsomes of 2-FAA-treated rats. Inhibition by carbon monoxide indicated that either cytochrome P-450 or P 1-450 is the terminal oxidase in N-hydroxylation by microsomes of 2-FAA-treated rats. Unlike pretreatment of rats with phenobarbital or 3-methylcholanthrene, pretreatment with 2-FAA did not appear to induce the synthesis of microsomal hemoprotein. The activities of NADPH-cytochrome c reductase, NADPH-cytochrome P-450 reductase and of amine oxidase in microsomes of 2-FAA-treated rats were not increased and thus did not account for the stimulation of N-hydroxylation. The induction, by 2-FAA, of a heretofore unknown electron carrier associated with the hepatic mixed-function oxidase is postulated and under investigation.

Optimal reception of digital data over the Gaussian channel with unknown delay and phase jitter

Asymptotically optimum (in the sense of minimum per-symbol error rate) receiver structures for data communication over the white Gaussian channel with unknown time delay and carrier phase jitter are developed. The receiver structures apply to the following suppressed-carrier modulation systems: double sideband (DSB), quadrature amplitude modulation (QAM) with an arbitrary constellation, vestigial sideband (VSB) and single sideband. The resulting minimum error probability receivers are asymptotically equivalent to maximum-likelihood digital {\em sequence}-estimating receivers. The optimum structures implicitly derive joint maximum-likelihood estimates of the unknown parameters and of the sequence of data symbols. It is shown that the parameter estimates can be obtained from two data-directed stochastic approximation algorithms. Unlike traditional theoretical treatments of this communication situation, which have separated the highly important carrier phase and timing recovery problem from the detection problem, a unified theory is presented from which the complete ideal receiver structure can be deduced.

Electron transport and photophosphorylation in chloroplasts as a function of the electron acceptor. II. Acceptor-specific inhibition by KCN

1. 1. Dark pretreatment of chloroplasts with high concentrations of KCN in the presence of a trace of ferricyanide completely blocks subsequent transfer of electrons from water to hydrophilic acceptors such as ferricyanide and methylviologen. In the KCN-treated chloroplasts there is still a largely uninhibited electron flow from water to lipophilic oxidants such as p-benzoquinonediimide (oxidized p-phenylenediamine), duroquinonediimide (oxidized diaminodurene) and 2,5-dimethyl- p-benzoquinone. The cyanide-insensitive electron transport supports phosphorylation with a P/ e 2 ratio of 0.3 to 0.4. It is concluded (a) that these lipophilic oxidants can accept electrons from an unknown intermediate carrier, X, which precedes the KCN-inhibition site and is inaccessible to hydrophilic oxidants, and (b) that a phosphorylation site is associated with the electron pathway H 2O→X. 2. 2. Electron transport from diaminodurene to methylviologen and the associated phosphorylation are both inhibited by KCN. The same is true of cyclic photophosphorylation reactions catalyzed by diaminodurene, reduced dichlorophenolindophenol, pyocyanine, and low concentrations of N-methylphenazonium methosulfate. However, cyclic photophosphorylation can be largely restored by high concentrations of PMS. 3. 3. Isolated plastocyanin reacts readily with high concentrations of KCN (> 10 mM) but only at the relatively high pH values (> 7.5) required for effective KCN treatment of chloroplasts. It is suggested that this copper protein is the site of KCN inhibition in chloroplasts. 4. 4. Photoreduction of p-benzoquinonediimide is extremely sensitive to Photosystem II inhibitors, such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and the inhibition is completely independent of light intensity. In contrast, although the reduction of ferricyanide is almost equally sensitive at very low light intensities, the sensitivity decreases as the light intensity increases. It is suggested that the lipophilic reduction site, X, may be located close to Photosystem II.

Biohydrogenation of Unsaturated Fatty Acids: VI. SOURCE OF HYDROGEN AND STEREOSPECIFICITY OF REDUCTION

Abstract The biohydrogenation of either linoleic acid or cis-9, trans-11, cis-13-octadecatrienoic acid (punicic acid) by Butyrivibrio fibrisolvens results in the formation of trans-11-octadecenoic acid. Incubation of whole cells with tritiated formate, tritiated succinate, and glucose labeled with tritium in various positions failed to result in the labeling of the monoenoic acid product. In contrast, experiments performed in D2O indicated that deuterium was incorporated at the cis double bond(s) reduced by the microorganism. This reduction, which takes place stereospecifically, was found to occur by cis addition to the d side of cis-9, trans-11-octadecadienoic acid, an intermediate in the biohydrogenation of linoleic acid. The distribution of deuterium at the reduced carbon atoms shows an isotope effect and leads to the speculation that reduction occurs by addition of a proton and hydride ion mediated by an unknown carrier.

Recherche de plusieurs transporteurs d'electrons, notamment des cytochromes b-559 et c-553, chez trois mutants non photosynthetiques de Chlamydomonas reinhardi

Studies of several electron carriers, particularly cytochromes b-559 and c-553 in three non-photosynthetic mutants of Chlamydomonas reinhardi Biochemical and spectroscopic analyses were performed in order to investigate the electron-carrier contents of three non-photosynthetic mutants ( Fl 5, Fl 9 and Fl 15) of Chlamydomonas reinhardi. These mutants exhibit several physiological amomalies, which indicate a blocking of the internal electron transport close to Photoreaction II. Quinones and soluble proteins were analysed by chromatography. With the insoluble cell debris, difference absorption spectra were measured at 20° and at −190°. The plastoquinone A, soluble cytochrome c-553, plastocyanin, ferredoxin and ferredoxin-NADP + reductase contents of each mutant and of the wild type were comparable. Cytochrome b-559, also, was present in the four strains. But it appeared that the mutants Fl 9 and Fl 15 showed only traces of the insoluble (bound) form of cytochrome c-553; this insoluble form was present, in appreciable amounts, in the wild type and in the mutant Fl 5. The wild type contained about: I molecule of cytochrome b-559 per 130 molecules of chlorophyll ( a+ b) and I molecule of bound cytochrome c-553 per 500 molecules of chlorophyll. It seems probable that the mutants are affected by structural defects, wich may be of a different nature for Fl 9 and Fl 15, on the one hand, and for Fl 5 on the other. However, the possibility of the lack of an unknown electron carrier in these mutants cannot be ruled out.

A "sporadic" case of typhoid fever.

To the Editor:— Thyphoid fever in the United States has declined steadily during the past 25 years. 1 Infections caused by other Salmonella strains, notably those that are avian related, have increased or remain unabated. 1,2 The reason for this disparity is that S typhi is uniquely pathogenic to man while other strains responsible for salmonellosis occur widely in nature. Approximately 3% of those people infected with S typhi become carriers. Surveillance of the human carrier and contemporary sanitation are the major factors responsible for the decline in infection due to S typhi. The following report of an isolated case of typhoid fever describes how comprehensive study resulted in the recognition of a previously unknown carrier. Report of a Case:— A 19-year-old girl was hospitalized after four days of progressive anorexia, chills, fever, headache, and vomiting. She had been healthy and had recently begun employment as a nurses' assistant. The

Phase Measurement Accuracy with Modulated Sounding Signals

In this paper the problem of measuring an unknown carrier phase shift of a transmitted sounding signal in a Gaussian noise channel is considered. Receivers which minimize the probability that phase error is larger than some value are considered. In some cases, this criterion leads to simple phase measurement techniques. When it does not, suboptimum receivers are considered. The main objective is to determine the effectiveness of the various measurement techniques by finding the cumulative probability distribution of phase error. In this way, three sounding signals are compared: an unmodulated carrier, a binary phase shift keyed (PSK) carrier, and a Gaussian pulse amplitude modulated carrier.