Multipolar Configurations Research Articles

Polarity and International Stability

In his article in the June 1991 issue of thisReview, Ted Hopf challenged the argument that bipolar systems are inherently more stable than multipolar configurations of power. He reported that the international situation in sixteenth century Europe became only marginally more stable with a shift from a multipolar to a bipolar system. He argued for attention to the offensive-defensive balance, rather than systemic polarity. Manus Midlarsky accounts for Hopf's findings, and for evidence of multipolarity and increased conflict in the early seventeenth and twentieth centuries, by proposing a relationship between polarity and war that is contingent on scarcity of desired international resources. Midlarsky argues for more attention to contingent relationships generally and draws implications for current and future probabilities of conflict in a multipolar world. Hopf responds by pointing out the need for further development of Midlarsky's analysis, the possible compatibility between Midlarsky's formulation and his own focus on the offensive-defensive balance, and the desirability of a productive unity of the two research programs.

On some peculiarities in the evolution of the McMath 16051 flare active region on 2–7 June, 1979

The active region McMath 16051 showed during 2–7 June, 1979 a complex multipolar magnetic configuration, in which separate bipolar systems interacted. The period of high flare activity of 3–5 June was characterized by a rapid change in magnetic flux imbalance with the rate of 1.65 × 109 Wb s−1, while the period of low flare activity was typified by a synchronous decrease of the N- and S-polarity fluxes, with balance between them remaining unchanged. The high flare activity period exhibited the following structural features of the photosphere in the sunspot group: thin, thread-like bright bridges in sunspot kernels and complex dynamic penumbral structure, with superimposition of two systems of fibrils.

Investigation of the influence of electromagnetic excitation on electron cyclotron resonance discharge properties

The influence of the permanent magnet configuration, electromagnetic excitation mode, and input microwave power on the operation of a multipolar electron cyclotron resonance (ECR) source is investigated. A 12.5-cm i.d. multipolar ECR plasma source was operated in argon gas at 0.77 mTorr with a flow rate of 20 sccm. The input power was varied from 240 to 750 W. The microwave coupling efficiency, the ion density and uniformity, and the ion production efficiency were determined for three different multipolar magnetic field configurations (8 pole/8 magnet, 4 pole/8 magnet, and 4 pole/4 magnet) and two electromagnetic modes (TE211 and TE311). The 4 pole/8 magnet configuration operated in the TE211 mode had the best efficiencies and uniformity. In particular, it had a microwave coupling efficiency as high as 98% and an ion production efficiency with 240 W of input power of 290 eV/ion. A numerical analysis of the ECR excitation indicated that this configuration excited with the TE211 mode also had the most uniform electromagnetic excitation of plasma by the microwave fields.

Polarity, the Offense-Defense Balance, and War

Bipolar systems are inherently more stable than multipolar configurations of power, Kenneth Waltz argues. His empirical justification for this conclusion relies on the multipolar systems that preceded the two world wars and the bipolar Cold War. The weakness of Waltz's argument is the small number of cases and the failure to consider alternative explanations for different levels of war in the three periods. In another historical period of both multi- and bipolarity—Europe from 1495 to 1559—I have found that polarity cannot account for the constant level of instability across a change in polarity in the system. Instead, the offense-defense balance, which includes the technical military balance, the cumulativity of power resources, and strategic beliefs, explains instability in the period. Drawing on this alternative theory, I reassess the high level of stability associated with the Cold War and speculate on the level of stability we can expect in the post-Cold War period.

1,6-Dinitropyrene causes spindle disturbances and chromosomal damage in V79 Chinese hamster cells

We have investigated the cytogenetic effect of 1,6-dinitropyrene (1,6-DNP) in Chinese hamster V79 cells. The chemical caused a dose-dependent increase in the incidence of initial and full C-mitoses, polyploid mitoses, ana-telophases with lagging chromosomes, non-disjunction and multipolar configurations, in a range of 0.05–5 μM. These findings indicate that 1,6-DNP interferes with the functioning of the spindle apparatus in V79 cells. Early signs of spindle disturbances were seen at 1,6-DNP concentrations which only moderately reduced cell growth and division. Analysis of structural chromosomal aberrations revealed the appearance of chromatid-type aberrations with open breaks and exchanges accompanied by gaps. The results indicate that 1,6-DNP is both a spindle-disturbing and a clastogenic agent in V79 cells.

A localized high multipolar conductor configuration for a magnetic limiter in TEXTOR

The radially disturbing magnetic field generated by an octopole configuration is Fourier analysed and its impact on the transport processes of the plasma in the boundary region of TEXTOR (a=50 cm) is assessed. The Fourier analysis showed that beyond the radius r=42 cm a magnetically mixed layer is established, where the overlapping of the islands corresponding to each resonant Fourier component is good. As the main figure of merit concerning the transport process, the mean inclination angle epsilon (r) of the field lines against the toroidal direction, is computed. For the coil current Jc=60 kA the maximum value of epsilon (r) is 2.10-3. For TEXTOR, with and without additional heating, the modelling of the boundary region shows that the magnetic limiter action reduces the edge temperatures by a factor 6, and 1.7, respectively, mainly because of the enhanced heat diffusivities. The recycled hydrogen flux is increased roughly by a factor 3, thereby enhancing the electron density at the limiter edge by around a factor 1.6.

Screening efficiency of the magnetically mixed layer generated in the boundary region of the TEXTOR tokamak by a localized high multipolar conductor configuration

The impurity transport in, a magnetically mixed layer is investigated on the basis of the average ion model and a two-dimensional model for the neutral impurity atoms. The magnetic field structure is globally described by the mean inclination angle of the field lines against the toroidal direction. The radial dependence of this angle is computed from the data of the specific perturbation coil which is foreseen for the TEXTOR tokamak. The particle and energy flux densities in the magnetically mixed layer are essentially derived from the inclination angle, the partial pressures of the different species, and the friction between the hydrogen ions and the impurity ions. The calculations show that the impurity density profiles become hollow in the boundary layer. The central iron density is decreased by a factor of 4 and the neutral oxygen concentration is increased by a factor of 30.

Chandelier cells in rat visual cortex.

Golgi-impregnated chandelier cells in rat visual cortex have been examined by both light and electron microscopy. All of the chandelier cells impregnated have their cell bodies within layer II/III and although they occur throughout area 17, there are increased numbers at the area 17/18a border and to a lesser extent at the area 17/18 border. Most of the chandelier cells are bitufted neurons, with groups of dendrites extending from the upper and lower poles of an elongate cell body, but some cells have a more multipolar configuration. The perikaryal cytoplasm is rich in rough endoplasmic reticulum and both the cell body and the sparsely spinous dendrites receive axon terminals forming symmetric and asymmetric synapses. The axons of these neurons arise from either the lower pole of the cell body or the base of one of the dendrites in the lower tuft, and the axons form laterally spread plexuses which terminate in vertical strings of boutons. The boutons in each string synapse with axon initial segments of layer II/III pyramidal cells, the uppermost bouton in each string being 7 to 14 micrometers distant from the pyramidal cell body. Some layer II/III pyramidal cells seem to receive boutons from more than one chandelier cell, others from a single chandelier cell, and still other appear to receive no chandelier cell terminals. The axon terminals of the chandelier cells are irregular in shape, contain pleomorphic synaptic vesicles, and form symmetric synapses. Evidence is presented to show that axon terminals exhibiting the same morphological features and site of synaptic termination as those of the chandelier cells contain glutamic acid decarboxylase (GAD), the enzyme which synthesizes GABA. Hence the chandelier cells are probably GABAergic, inhibitory neurons. Other GAD-positive axon terminals synapse with the cell bodies, axon hillocks, and proximal portions of the axon initial segments of the layer II/III pyramidal cells, and these terminals are probably derived from the smooth and sparsely spinous stellate cells.

Definition of a cell clone with astroglial characteristics derived from a chemically induced rabbit brain glioma

Three-month-old rabbits were started on a fortnightly schedule of intravenous injections of N-methyl-N-nitrosourea. All but two of the central nervous system tumors induced in this manner were propagated in culture as permanent cell lines. On the 76RB-G-414-H line established from a grade 2 astrocytoma of this series of neoplasms, a cloning procedure was carried out using a laser microbeam. The clonal line originated in this way has been maintained in long-term culture and given the 76/RB-G-414-H-C designation. The cells of the clone display invariably a bipolar or multipolar configuration with long processes. Intermediate filaments are common and even abundant in some cells. Positivity for S-100 and GFA proteins is a regular finding in these cells. In addition, dibutyryl cyclic adenosine monophosphate treatment reduces cell division and stimulates cell process formation of these cells. Thus, it appears that we succeeded in establishing in vitro and maintaining in long-term culture a clone of tumor cells with astrocytic characteristics.

Intracellular recording and staining of cat's lateral geniculate neurons

Intracellular staining with recording micropipettes filled with a Procion yellow solution was attempted on 11 lateral geniculate neurons of chloralose-anesthetized cats for the purpose of correlating electrophysiologically identified cell types with morphologically identified cell types. Five neurons were successfully stained: one was located in lamina A and the others in lamina A1. They were all identified as P-cells on the basis of their responsiveness to electrical stimulation of optic disc, optic chiasm and visual cortex. The conduction velocities and synaptic delays for specific optic nerve fibers concerned with these P-cells were estimated from the relationship between latency and conduction distance. Intracellular staining has revealed that a neuron located in lamina A and three of four neurons located in lamina A1 had multipolar configuration, with their main dendrites oriented parallel to the plane of the laminae; while one neuron located in lamina A1 had a configuration similar to that of a class II-type neuron described by Guillery in his Golgi preparations. In these experiments no neurons located in lamina B, central interlaminar nucleus and medial interlaminar nucleus were stained. No interneurons were obtained, either.

In situ analysis of normal and abnormal patterns of the mitotic apparatus in cultured rat-kangaroo cells.

Dividing cells in monolayers of the rat-kangaroo (Potorous tridactylis) cell line Pt-K1 have large spindles and are flat, thus making possible studies of interactions between the achromatic and chromatic parts of the mitotic apparatus during the cell cycle. At prophase, asters and centrioles seem to exert pressure on the nuclear membrane leading to its rupture and penetrance of the centrioles. Apparently, the long axis of the spindle is shorter than the nuclear diameter. What appears as persistent, large portions of the nuclear membrane were observed in some metaphase and anaphase cells. Such a condition might also indicate an arrested mitosis. The midbody, which was often bipartite, was found to be of a ribonucleoprotein nature. — Three-group metaphases were of common occurrence and might represent early stages of chromosome orientation preceding the final alignment of the chromosomes on the equatorial plate. They could also be an expression of an anomalous condition as a result of mitotic arrest during prometaphase owing to spindle inactivation or breakage, errors in centromere-spindle attachments, interference with chromosome movement, or a duplicated centriolar constitution. Most of these aberrations could be attributed to the flatness of dividing cells, which might also bring about the failure of centriole separation and spindle organization in prometaphase stages, as well as multipolar mitosis.De novo organization of half spindles might take place in cells with ruptured spindles. Anaphase cells showing signs of a previous three-group orientation were rare. — Multipolar mitoses were prevalent mainly in cells with high chromosome numbers. They were often star-shaped with the chromosomes oriented between opposite and adjacent poles, and rarely as end-to-end associations of spindles. Apparently, one or more centrioles might share a common polar region. Multipolar configurations have either a mono- or multinuclear origin. Nuclei usually enter division synchronously in binucleate cells and the spindles become organized between centrioles associated with individual or different nuclei.

Studies on Chemically Induced Change in Expression of Gene(s) Controlling the Pollen Shapes inPimpinella Monoica

Summary Pollen variability in Pimpinella monoccia was artificially induced by treating seedlings with different chemicals. Positive results in the treated plants were obtained with acsculine, saponin, α-bromonapthalene and 8-hydroxy-quinolene. All these plants were 2n. Their meiosis was typified by multiple and multipolar spindles, laggards, strays, bridge-fragment configuration, spindle breakdown and unequal division of the chromosomes into many groups giving rise to variable number of spores at the sporad stage. Besides polyads the variable grains were asymmetric and nonfixiform while the controls had all radiosymmetric grains. One of the interesting facts was that similar pollen shapes were induced by all these diverse chemicals. The development of variable grains has been traced with the help of a scheme. The causes of pollen variability are discussed.