Negative Needle Research Articles

Conditioning Effect of Dielectric Breakdown in Liquid Helium

In a non-uniform field with a needle-plane electrode system, the breakdown voltage Vb of a positive needle decreases as the number of breakdown events N increases, but that of a negative needle increases slightly with N. In a uniform field, the breakdown voltage decreases with increasing N. However, when the polarity of the voltage pulse is reversed after many breakdown events, Vb increases suddenly and then again decreases slightly with increasing N, tending to saturate. These conditioning effects can be explained by the increase of the electron injection from the cathode due to the formation of a rough surface by the previous breakdown events.

Dependence of polarity effect of dielectric breakdown on molecular structure of liquids

In liquid hydrocarbon, at short electrode distance, the negative needle indicates lower strength than that of positive needle and it reverses at longer electrode distance. The critical distance of this polarity reversal is very short for liquids with large electron mobility like neopentane. In perfluorocarbon liquids, the difference of breakdown voltage for both polarities is much less than that of hydrocarbon liquids. In liq.N 2, the polarity effect of breakdown is similar to that of hydrocarbons and strongly dependent on pulse width, applied pressure. The polarity effect in liq.He is completely different from other liquids and due to the unique behaviour of electrons in liq.He. The polarity effect in liq.Ne is similar to liq.He. These polarity effects in various liquids seem to have some correlation with the mobility in these liquids and are discussed in terms of bubble process and electronic processes like streamer.

Pressure Dependence of Dielectric Breakdown in Liquid Nitrogen

Breakdown voltage characteristics in liquid nitrogen (liq.N2) have been studied in the pressure range between 1 and 15 atm. For constant gap length, the breakdown voltage increases with increasing pressure and saturates at around 10 atm. For shorter pulse width, the increase in breakdown voltage with pressure becomes less remarkable. In a non-uniform field of a plane-needle electrodes system, the breakdown voltage of the negative needle configuration increases remarkably with increasing pressure but that of the positive needle is almost insensitive to the pressure. These results can be interpreted in terms of the suppression of the formation and the development of a gaseous bubble in the breakdown of liq.N2 under high pressure and at short pulse width. The positive streamer seems to play an important role in initiating total breakdown under high pressure and at short pulse width.

The Solitary Thyroid Nodule-Reply

In Reply.— There is no best way to ascertain clinically which solitary cold thyroid nodule is malignant. Mature judgment will lead to one or a combination of diagnostic tools. Our publication assessed prospectively the value in predicting cancer of the two following approaches that are commonly used and about which there are little hard data: (1) factors derived from the history and physical examination that are immediately available to the average primary physician without a consultant, and (2) the response to three months of suppressive therapy. Three fourths of our cancers came from the high-risk group, and in these patients neither suppressive therapy nor needle biopsy was needed to make an accurate diagnosis. Since 50% of this group had carcinoma and 30% adenoma, it is clear from our results that when there are high-risk factors a negative needle biopsy result should not deter surgery. The majority of the patients, those

Yield from Routine Prostatic Needle Biopsy in Patients more than 50 Years Old Referred for Urologic Evaluation: A Preliminary Report

Approximately 10 per cent of the patients undergoing simple prostatectomy for presumed benign disease have clinically unsuspected prostatic carcinoma. In these patients curative treatments, such as radical prostatectomy and some forms of radiation therapy, often are compromised by the simple prostatectomy. To determine whether routine prostatic needle biopsy would be practical to identify patients with occult carcinoma a prospective study has been initiated of routine needle biopsy in patients more than 50 years old referred for urologic evaluation. To date 71 consecutive patients have been biopsied, 21 of whom underwent subsequent simple prostatectomy after negative needle biopsy. Carcinoma was found in none of 24 men not having prostatic induration, 4 of 36 (11 per cent) with minimal induration and 5 of 11 (45 per cent) with marked induration. The results indicate that the vast majority of the patients with prostatic carcinomas has some degree of palpable induration and that a high index of suspicion appears warranted when any prostatic induration is present on digital rectal examination

Anomalous polarity effect of dielectric breakdown voltages in liquid helium

The polarity effect of the dielectric breakdown voltage in liquid He is studied. The breakdown voltage for a positive needle is higher than that for a negative needle and even than that for uniform field. The field strength on the cathode surface at breakdown threshold for a positive needle is calculated with a simple hyperboloid approximation of field distribution, and agrees approximately with the breakdown field in the uniform field condition. The breakdown strength also depends on the work function of the cathode metal but not that of the anode metal. Therefore, breakdown threshold in liquid He seems to be determined by the field strength at the cathode.

Electrical breakdown in cryogenic liquids

Both the statistical time lag T s and the formative time lag T f of the breakdown in cryogenic liquids (Liq.Ar, N 2 and He) are evaluated from the Laue plots of the breakdown time lag induced by a voltage pulse having a 100-ns pulse width. In the case of Liq.Ar, both T s and T f become shorter with increasing applied voltage, and T f increases with increasing electrode distance under the constant electric field. Therefore, these experimental results are interpreted in terms of a single avalanche mechanism. On the other hand, in the case of Liq.N 2, T s decreases with increasing electric field, but T f does not depend strongly on the electric field. In Liq.He at both 4.2 K and 2.1 K, T s and T f show a similar tendency as with Liq.Ar. In Li He, the threshold breakdown field decreases with increasing electrode distance and voltage pulse width. The carrier mobility, estimated from T f by assuming a single avalanche breakdown, is nearly the same as that obtained by the time-of-flight method in Liq.Ar. In Liq.He, however, the former is larger than the latter obtained at low fields. Under the non-uniform electric field (plane-needle electrode configuration), the breakdown strength at negative needle configuration is much higher than that at positive needle in Liq.Ar. On the contrary, in Liq.He the former is much lower than the latter. These experimental results can be interpreted by taking into consideration the different mobilities of negative and positive carriers in these liquids.

Studies of the breakdown process in dielectric liquids using high speed photography

The present paper is concerned with high-speed photographic studies (using an image converter camera, an image intensifier and the Schlieren system) of the electrical breakdown process under a voltage pulse applied to a needle-plane gap immersed in such dielectric liquids as n-hexane, benzene, insulating oil (mineral oil), carbon tetrachloride (CCl 4), water etc. Various aspects of the breakdown process, and the polarity effect and mean velocity of streamer propagation have been investigated. In addition, high-speed spectroscopic studies on streamer discharge in dielectric liquids have also been carried out. It is experimentally observed that the mean velocity (ν m) of positive streamer propagation may be divided into two groups: fast and slow. In the fast group are liquids containing chlorine in their molecules and a polarity effect on ν m is also observed in these liquids. Generally, ν m for the positive needle was about ten times larger than that for the negative needle in all liquids under test. From the results of high-speed spectroscopic studies, it is ascertained that electrical breakdown in a liquid is accompanied by dissociation, excitation, and ionization of the liquid molecules. It is also observed that the spectrum of the electrode material and the spectrum of the solute in water solution can be seen under certain conditions.

Electrocochleographic Study on Effect of White Noise Exposure in Guinea Pig

In order to detect NITTS and NIPTS in guinea pigs, the influence on the latency of AP (N1) after white noise exposure was studied electrocochleographically. In this series, the guinea pigs were 250 grams to 500 grams of body weights with normal Preyer's reflex.Electrocochleographic recordings were repeated several times before and after white noise was exposed to the animals under general anesthesia with pentobarbital sodium (45mg/kg i. m.). The stimulation sound used in this study was click, and was given through a ear tube. A positive needle electrode was placed in the external ear canal, and a negative needle electrode in the ipsilateral ear lobe, and the ground in the ipsilateral leg. The responses were averaged 200 times and recorded on a X-Y recorder. The experimental conditions of white noise exposure were as follows:The results were as follows:1. Under the experimental conditions of A, B, C, D and F, the latency of AP was prolonged immediately after white noise exposure. However, one day after or one week after white noise exposure the latency of AP returned completely to the pre-exposure level. In these experimental conditions, therefore, white noise exposure were considered to induce NITTS in the guinea pigs.2. Contrary to the above, in the experimental conditions of E and G, the latency of AP was prolonged even one week or 2.5 months after white noise exposure. Thus, these two experimental conditions were considered to have induce NIPTS in the guinea pigs.3. From these two results, the latency of AP in electrocochleography was considered to be one of the parameters to detect NITTS and NIPTS in the guinea pigs.

Tree Initiation in Polyethylene by Application of DC and Impulse Voltage

The results of tree-initiation tests using impulse voltages show that the time required for the build-up of space charge at 25C is 30μs~80μs. The results of prestressing tests with DC and superimposing impulse voltages show that the space charges are homo-charges. An investigation of tree-initiation in polyethylene was carried out using dc and impulse voltages, the latter having a wave-front duration ranging from 1 μs to 700 ps. The relationship between the tree-initiation voltage and the duration of the wave-front of the impulse voltage shows that the times required for the build-up oif the space charge at the tip of a needle electrode are 30μs~140μs at 40C for both polarities and greater than 700 μs for the positive needle and 80μs~l40μs for the negative needle, respectively at 60C. The tree i Ltiation voltage decreases when the impulse voltage is superimposed on a dc voltage of the opposite polarity and increases when the impulse voltage and the dc voltage are of the same polarity. Some of the samples were prestressed with dc voltage for 10 minutes, and were then subsequently tested by applying an impulse voltage with a wavefront duration of 1 μs after a waiting period of 2, 30 and 60 minutes, respectively. The tree-initiation voltage was reduced in a similar manner as when an impulse was superimposed on a dc voltage of opposite polarity.

The Sparking Characteristics of Needle-To-Plane Coronas

The sparking voltage (V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> ) and maximum presparking corona current (I <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</L> ) of needle-to-plane coronas have been measured as independent functions of polarity, tip radius (r), and needle-to-plane spacing (S). For a negative needle, V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> and I <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</L> increase with S but are independent of r. For positive polarity, V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> and I <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</L> increase with both S and r. Thus to increase the corona current while avoiding a spark, one should increase the spacing and voltage. At large spacings, I <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</L> is appreciably greater for negative polarity than for positive. Analysis of the data reveals that for negative polarity the maximum presparking current may be written in the approximate form I <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</L> ∝V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> (V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> -V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</L> )S <R xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</R> where V <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</L> is the corona threshold voltage. This is an extrapolation of a relationship previously obtained for Trichel pulse corona. The analysis shows that the transition from negative corona to sparking occurs when the linear space charge density in the gap reaches a critical value Q <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> /S ≅10 <R xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</R> coul/mm, where Q <L xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</L> is the total space charge in the gap just before sparking occurs. It is shown that this condition amounts to spatial overlap of the multiple ion clouds in the gap, thereby creating a continuous ionized channel between the electrodes.

Interaction of the `Trichel' current pulses of a pair of negative coronas

The interaction of Trichel current pulses of neighbouring negative needle coronas is investigated. As the needles are brought together and the strength of the coulomb interaction increases, the experiments show that (i) the pulse frequencies decrease, (ii) the frequencies converge, and (iii) the relative phase of the pulses approaches π. A coupled circuit model of the interaction between the charge clouds is presented which shows that these observations are dictated by energy considerations. Localized Trichel corona spots also occur on negative corona wires, and the behaviour of these discrete discharge spots is explained by experiments and analysis.

Confidence in the negative transrectal needle biopsy : H. Zincke, J. T. Campbell, D. C. Utz, G. M. Farrow, and M. J. Anderson — ( 136: 78, 1973)

Confidence in the negative transrectal needle biopsy : H. Zincke, J. T. Campbell, D. C. Utz, G. M. Farrow, and M. J. Anderson — ( 136: 78, 1973)

Frequency of Corona Discharge Trichel Pulses in Air Flows

A phenomenological study was made to determine to what extent air streams affect electrical discharges between a negative needle and a plane at atmospheric pressure. When such discharges were operated at a constant current, first in still air and then with a wind blowing in the direction perpendicular to the gap axis, it was found that a lesser voltage was required to maintain the constant current in the latter case. In general, the repetition frequency of Trichel pulses is known to be approximately proportional to the gap current. We found that the blowing of a wind between the electrodes resulted in a pronounced decrease in the frequency, i.e., an increase in the average number of charges per pulse at constant gap current. These observations demonstrate the effect of current enhancement in windblown coronas, a phenomenon which is due to the removal of the negative ions which tend to reduce the electric field in the vital cathode region.

Angiographic diagnosis of malignant disease of the liver.

Hepatic Angiography by selective catheterization of the celiac or hepatic arteries is a useful procedure to evaluate the liver for malignant disease. Bierman et al. in 1951 (1) first described in vivo hepatic angiography applied to the study of hepatic neoplasia. Unfortunately, their technic, utilizing a catheter inserted by arterial cut-down, was fraught with hazard (2) and therefore was impractical for general use except as an investigative effort in terminally ill patients. With percutaneous catheter introduction, as devised by Seldinger (3), hepatic angiography was facilitated. In 1958, Odman (4) reported 61 cases of selective celiac angiography by the percutaneous approach. This paper will present the findings of hepatic angiography in 40 cases of malignant disease drawn from a total experience of 200 cases of selective celiac, hepatic, and superior mesenteric angiography performed at the Massachusetts General Hospital, Boston, Mass. Methods and Materials Selective celiac and selective hepatic angiography was performed by the Seldinger technic of percutaneous catheter introduction, usually through the femoral route, although occasionally left brachial or left axillary approaches were utilized. A preshaped Kifa catheter was employed and 30 to 50 cc of 76 per cent methylglucarnine diatrizoate was injected under pressure. With a serial film-changer films were obtained at the rate of 2 per second for eight seconds and 1 every third second for an additional twenty seconds, in the anteroposterior projection. Frequently, oblique projections were obtained and additional injections were performed. A replaced or accessory hepatic artery originating from the superior mesenteric artery occurs in 14 per cent or more of cases (5, 6), and in such instances superior mesenteric artery catheterization is required. Results The accuracy of this technic in 71 cases is recorded in Table I. Proof was obtained by autopsy, laparotomy, or positive needle biopsy. Negative needle biopsies were not included in this number since neoplastic involvement could easily be missed by a percutaneous biopsy. Because a negative surgical exploration does not absolutely rule out the presence of tumor, no attempt to draw statistical conclusions about negative cases was made, but the results show that a negative angiogram does not necessarily exclude the presence of tumor in the liver. The accuracy of positive interpretations, however, was 92 per cent. Of 40 cases of hepatic neoplasms, 33 were proved; the remainder showed characteristic angiographic findings, and a clinical course and laboratory data were consistent with malignant. disease in the liver. Although the origin of the hepatic arteries is variable, the intrahepatic arteries normally reveal a random arborization of the left and right branches, gradually tapering in a smooth fashion and showing a uniform intrahepatic distribution of the fine branches.

SUPERFLUOUS HAIR

Hypertrichosis is considered by the sensitive woman a most unsightly, humiliating, masculine blemish. It not only is a social and economic disadvantage but serves as a physical basis for a melancholic psychic disturbance, and it is a mistake merely to console the patient. Dermatologists have accepted two energized needle methods as satisfactory for removing superfluous hair. Electrolysis utilizes a needle energized by galvanic current, and the diathermy method utilizes a needle carrying high frequency current. Electrolysis presents many complicating features which make the operation much less certain than merely inserting a needle and adjusting a rheostat would indicate. If the electrodes are reversed (and two must be used), whether by accident or by ignorance, the result is the formation within every follicle entered by the needle of a black dot or tattoo mark. But if used on the negative terminal steel needles are satisfactory regardless of the glamour which lay