Dense Column Research Articles

Mouse spleen lymphoblasts generated in vitro. Their replication and differentiation in vitro.

Mouse spleen lymphoblasts induced with lipopolysaccharide and fetal calf serum were obtained in high yield and purity in their first proliferative cell cycle by floatation in dense bovine plasma albumin columns (3). The blasts were maintained in vitro for 3 more days. The cultures were examined in bulk on each day, and in addition, those cells in S phase initially were tagged with [(3)H]thymidine and followed continuously in vitro. Grain count dilution data indicated that most blasts divided but twice over a 2- to 3-day interval in vitro. [(3)H]Thymidine pulse radiolabeling and flow microfluorometry suggested that at least 50-70 percent of the proliferating blasts withdrew from proliferative activity after 2-3 days of culture. Morphologic studies demonstrated that lymphoblasts persisted as such for 1-2 days in vitro and then matured into typical plasma cells. Many of the blastprogeny had small nuclei and considerable basophilic cytoplasm on Giemsa-stained cell smears; abundant rough endoplasmic reticulum by electron microscopy; and readily detectable cytoplasmic Ig by immunocytochemistry. Reversion of blasts to small lymphocytes could not be detected; however, some blasts persisted even after 3 days of culture. The viability of the cultured lymphoblast was followed by initially tagging the cells with [(3)H]thymidine as well as several other techniques. Little cell death was documented during the first day of culture. The number of labeled progeny increased twofold whereas the grain count halved. But 40- 50 percent of the cell-associated label was lost during each of the second and third days, and fewer labeled progeny than predicted by grain count dilution were identified. The culture medium could not be implicated in this loss of lymphoblast progeny, and we suggest that the maturation of the lymphoblast to a short-lived plasma cell was responsible. Therefore mitogen-stimulated B blasts seem to mature into typical plasma cells after just two cycles of cell division. The plasma cells resemble those produced in situ during an immune response in their cytologic features, withdrawal from active proliferative activity, and short life-span.

Projections from cortical visual areas 17, 18, and MT onto the dorsal lateral geniculate nucleus in owl monkeys

Projections from cortical visual Areas 17, 18, and MT to the dorsal lateral geniculate nucleus of owl monkeys were revealed by the use of the autoradiographic tracing method. Restricted injections of 3H-proline into Area 17 resulted in dense columns of labeled tissue extending through all layers of the nucleus and roughly perpendicular to the layers. There was some lateral spread of the label in the interlaminar zones. Projections from Areas 18 and MT were distributed over the ventral layers of the nucleus including the magnocellular layers, layer S, and the adjoining interlaminar zones. The input from Area 18 was relatively sparse. The projections from all three cortical visual areas appear to connect homotopic locations in the geniculate and cortical representations of the visual field.

Practical factors affecting cathode performance in ion sources of the Nier-Bernas type

To understand the influence of cathode design on the characteristics of the source arc, the intensity distribution of the arc, generated by a simple cathode, was observed under different conditions of source parameters, by scanning across the arc column with probes inside the ionization chamber. Two main phenomena were observed: 1. a) a deflection of the arc column in the beam direction due to the magnetic field of the cathode heating current, 2. b) a lateral asymmetry in the arc density due to the ohmic voltage drop on the cathode, especially in the pressure-limited mode of arc operation. As a consequence of these results, a short-legged helical cathode was designed which produces a dense symmetric plasma column with stable location relative to the emission slit. Thus, the two disturbing effects mentioned above were eliminated and, at the same time, the cathode efficiency was enhanced. Preliminary observations with the helical cathode at low hash conditions have shown that the source efficiency was increased by a factor of 1.8 for beam currents of 20 and 30 mA. Further, the life of the helical cathode is estimated to be at least twice that of a standard U-type cathode for the same output.

Transient flow and expansion of a pinch discharge plasma in self-induced magnetic fields

The formation of a dense argon plasma column in a linear Z-pinch and the ejection of the plasma through an axial orifice electrode are investigated photographically, and with electric, magnetic and piezoelectric pressure probes. The plasma-magnetic field interaction and gas dynamic flow transients in the exhaust are also studied. Pronounced orifice electrode polarity effects on the plasma acceleration and ejection mechanisms are observed. It is found that the distribution and dynamics of the ejected plasma cannot be established from luminosity profiles. The development of plane blast waves in the far field flow is identified.

Microwave heating of electrons of a dense plasma column at frequencies higher than electron cyclotron frequency

In the overdense collisionless plasma column inserted through the narrow sides of a rectangular waveguide, the excited electron cyclotron harmonic waves (CHWs) are studied by means of two movable probes and a phase interferometer in the range of parameters of 2 >ω/ωce>1; 0·5 < (ωpe/ω)2 < 15.

Microwave heating of electrons of a dense plasma column at frequencies higher than electron cyclotron frequency

Microwave heating of electrons of a dense plasma column at frequencies higher than electron cyclotron frequency

Dense plasma columns obtained from hollow-cathode discharges

With a hollow-cathode arc discharge used as a plasma source, plasma columns with high densities and low electron temperatures are obtained; these characteristics make them suitable for beam-plasma interaction experiments in the UHF domain.

Free kinetosomes in Austrialian flagellates. I. Types and spatial arrangement.

An electron microscope study was made of Deltotrichonympha and Koruga, two closely-related hypermastigote flagellates that live in the hindgut of the Australian termite, Mastotermes darwiniensis These symbiotic protozoans have a typical flagellated rostrum and long body flagella. Their "giant centrioles" (centriolar apparatus) are large, fibrillar, and granular bodies which do not resemble typical centrioles in structure. The unique feature of interphase cells is the presence of more than half a million free kinetosomes in the anterior cytoplasm. Two classes of free kinetosomes, differing in length and spatial arrangement, were found. 500,000-750,000 short free kinetosomes are concentrated in a dense column which extends from the centriolar apparatus in the rostrum to the anterior side of the nucleus Most of the short free kinetosomes in the column are arranged end-to-end in chains of varying lengths. Within a kinetosomal chain, all of the individual kinetosomes face in the same direction with respect to their cartwheel ends In most flagellates, the short free kinetosomes are 0 07-0.13 micro long, and are remarkably similar in length within any cell Occasionally, cells with uniformly "longer" short free kinetosomes are found. 70,000-120,000 long free kinetosomes are scattered singly throughout the cytoplasm between the column of short free kinetosomes and the cell surface These long free kinetosomes are 0 4-0 7 micro long, similar in length to the kinetosomes of the body flagella, and are oriented parallel to the anterior-posterior axis of the cell. The significance of this remarkable accumulation of free kinetosomes is discussed.

Possible effects of magnetic field alignment on meteoric lonization

Field alignment of ionization along the earth's magnetic lines has been shown to result in enhanced scattering efficiencies, as in the aurora or as observed in the equatorial E region by Bowles, Cohen, Ochs, Balsley [1960], among others. It is of interest to consider also the effect of such field alignment on ionization that is initially formed as a thin dense column, such as a meteor trail, parallel to the lines of magnetic force. The tendency of the magnetic field to maintain this initial alignment could to some extent offset normal diffusion processes and result in unusually long trail durations. Such durations have often been observed on overdense meteors, but never adequately explained.

Myelographic identification of the dentate ligament.

The dentate ligament is a thin fibrous band situated on either side of the spinal cord. It separates the anterior from the posterior nerve roots. Its inner border is continuous with the pia mater and its lateral border is fixed at intervals to the dura mater by 21 triangular processes on each side. The first of these is attached to the dura mater opposite the margin of the foramen magnum, between the vertebral artery and the hypoglossal nerve, and the last near the lower end of the spinal cord at the level of D-12 or L-1. The lower end of the dentate ligament terminates in a two-pronged fork, the lateral prong forming the last dentate digit and the medial prong being prolonged along the side of the conus medullaris. The ligament is thicker in its cervical than dorsal section (1). The dentate ligament can be visualized in the lateral projection of a Pantopaque myelogram as a linear radiolucent shadow, its anterior and posterior surfaces being outlined by the opaque substance. Its visualization is facilitated by the use of at least 10 c.c. of the medium and a lateral projection. Because of its greater thickness, the cervical dentate ligament is more readily visualized than the dorsal portion. At times, the dentate ligament is not visualized as a linear radiolucent shadow (Figs. 1 and 2) but is indicated by a dense radiopaque column (Fig. 3), the posterior border of which outlines the dentate ligament as a result of collection of Pantopaque under its ventral surface. The dentate ligament has been visualized in 10 out of 23 lateral projections in 36 cervical myelograms, and 4 dorsal myelographic studies. The above interpretation of the linear radiolucent shadow on the lateral myelogram as the dentate ligament has been proved on cervical myelograms of fresh cadavers. In 5 fresh cadavers a laminectomy of the cervicodorsal spine was performed in prone position. The dura was opened along its midline posterior aspect from C-5 to D-2. The dentate ligaments were identified and silver clips were applied to the edge. In 2 instances, the clips were applied to the dentate ligament on both sides. A No. 14 rubber catheter was passed into the subarachnoid space with its tip placed at C-3. The dura was closed with interrupted stitches and water was injected through the catheter to refill the subarachnoid space in order to reproduce a condition simulating “normal” anatomical circumstance. After the arachnoid space had been filled with water, 10 c.c. of Pantopaque was instilled through the catheter. Air bubbles were led out from the subarachnoid space by manipulation of the neck and during the slow withdrawal of the catheter. The neck of the cadaver was placed in hyperextension and a roentgenogram was obtained in lateral projection. The silver clips were visualized in each instance in line with the radiolucent streak, the dentate ligament (Fig. 4).

The strength of meteoric echoes from dense columns

Abstract Calculations of the strength of the echoes from dense meteoric ionization columns have been made in the past by assuming that the trails behave like perfectly reflecting cylinders of that radius for which the refractive index is zero. It is shown that this procedure neglects the defocusing effect of refraction at greater radii. A general formula is obtained for the effect of refraction on echo strength. The maximum power returned from a large dense Gaussian distribution of ionization is found to be only 70 per cent of that assumed previously.

The Indian as an Ecological Factor in the Northeastern Forest

There is popular belief that discoverers of eastern North America found everywhere an unbroken forest of giant trees. belief has had much support our popular literature. In backdrop for Landing of Pilgrim Fathers, The woods against stormy sky their giant branches tossed (Hemans 1826). America's fireside poet made us aware that, This is forest (Longfellow 1847). It has been said that squirrel might have gone Maine to Louisiana by leaping from one giant tree to next (Bear 1951) ; might have travelled bough to bough for thousand miles without seeing flicker of sunshine on ground (Adams 1935) ; might indeed have travelled squirrel's lifetime without coming down out of white pines (Peattie 1950). vast, virgin forest recurs constantly in works of Parkman (1909 a, b). He pictures for us One vast, continuous forest . . . depths of immemorial forests, dim and silent as cavern. He paints Verrazzano off New England coast surveying the shadows and gloom of mighty forests. Between French and English colonies lay a broad tract of wilderness, shaggy with primeval woods. There was Maine, waste of savage vegetation; White Mountains throned in savage solitude; Adirondacks, mountain wilderness; Lake George lying in wild charm of untrodden mountains and virgin forests. Frontenac's army approached Onondaga among dense columns of primeval forest, and across Pennsylvania a prodigious forest vegetation . . . wrapped

ON AN ASCENT OF MOUNT HEKLA, AND ON THE ERUPTION OF FEBRUARY 27, 1878

ON February 27 last severe earthquakes were felt throughout the south-west portion of Iceland, particularly in the districts of Land, Rangarollir, Hreppa, and Fljotschlith, which are situated immediately to the south and south-west of Mount Hekla. Between 8 and 9 P.M. an intense illumination of the sky, at first believed to be actual fire, was seen to the south-east. This was found to be due to the reflection by clouds of the light emitted by molten lava within a subsidiary crater, or bocca del fuoco, as the Italians would call it, of Hekla. On the following day dense columns of smoke ascended from the crater, and quantities of volcanic ashes fell in the districts of Hreppa and Biskupstundur. The light was seen at Reykjavik, nearly seventy miles distant, and there appeared to be two vents of fire.