Small Horn Research Articles

A short horn with high E-plane directivity

The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -plane beamwidth of a small pyramidal horn can be substantially reduced by the addition of paxabolic cylinder flanges of the proper focal length. Analysis of this antenna involves both geometrical diffraction theory and conventional aperture techniques. In the numerical and experimental examples chosen the flanges halve the half-power beamwidth without severe bandwidth reduction. Consequently a lightweight compact horn is achieved.

Growth of myelinated lumbosacral ventral root fibers in kittens after early postnatal dorsal rhizotomy, dorsal rhizotomy and spinal cord hemisection, or sciatic neurectomy

The fiber-size distribution of myelinated lumbosacral ventral root fibers was studied in 14 kittens at various survival times after unilateral transection of corresponding dorsal roots at 8 days of age. In six animals an ipsilateral spinal cord hemisection was made in addition to dorsal rhizotomy. For comparison, two kittens were subjected instead to a unilateral sciatic neurectomy. The size spectra obtained from the ventral roots on the side of the lesion were compared with the fiber-size distribution in the same roots on the side not affected by the operation. In addition, three normal kittens were used as control animals. The findings show that neither the dorsal rhizotomy nor the combined dorsal rhizotomy and spinal cord hemisection had any measurable effect on the postnatal growth of the myelinated fibers in the relevant roots. The lesions resulted in a grave motor deficit which suggests that a normal function is not of any major importance for the growth in fiber size. After sciatic neurectomy the size spectrum of the myelinated fibers in ventral roots L7 and S1 showed a distinct shift to the left indicating a more severe retrograde degeneration of large than of small ventral horn neurons.

The horn bases of the Reedbuck &lt;i&gt;Redunca arundinum&lt;/i&gt;

The structure and function of the horn bases of the reedbuck Redunca arundinum are discussed. It is shown that the white colouration which often occurs is not caused by glandular secretion but by small horn particles which are shed, exposing the lighter coloured material underneath. The shining horn base probably plays a role in the display behaviour of males.

Radiological abnormalities in temporal lobe epilepsy with clinicopathological correlations.

In 73 patients with drug-resistant temporal lobe epilepsy submitted to an unilateral anterior temporal lobectomy the radiographs were studied to see if there were any correlation with the pathology subsequently found and with the outcome of the operation. A small middle cranial fossa, focal calcification, and temporal horn displacement are often better indices of the underlying pathology than temporal horn dilatation alone. In a small number of cases, however, radiological changes were seen on the side opposite to an unilateral EEG focus, thus suggesting bilateral disease.

The evolution of cranial display structures in hadrosaurian dinosaurs

A theory is presented that cranial crests of hadrosaurs were visual and acoustical display organs. Facial morphology and phylogeny of the Hadrosauridae and earlier theories of crest function are reviewed. The following hypothesis is presented: cranial crests, whether hollow or solid, served as visual signal structures, and hollow lambeosaur crests were also vocal resonators; all crests promoted successful matingswithinspecies,i.e., they served as premating genetic isolating mechanisms. The following predictions are tested and found to support the hypothesis: (1) hadrosaurs had well-developed eyes and ears; (2) external features of crests varied independently of internal structure; (3) crest variations were species-specific and sexually-dimorphic; (4) crest distinctiveness correlates with species diversity; (5) crest size tended to increase through time. The circumnarial depression on the side of the face in hadrosaurines housed an inflatable diverticulum of the nasal passage which served as a visual display organ. Primitive hadrosaurs (kritosaurs) possessed a small nasal horn used as a butting weapon in intraspecific combat. Because the weapon was also used in intimidative displays, narial diverticula evolved to draw attention to it. In the kritosaurBrachylophosaurusfighting was modified to ritualized head-pushing using the flat nasal “shield”. Saurolophines expanded the diverticula on to the elongated nasal horn, converting the weapon to a dominance rank symbol. In non-crested edmontosaurs, enlarged diverticula assumed a vocalization function. Lambeosaurs created resonators by enclosing the diverticula in bone; they further enhanced the resonator function of the nose by forming elongated “organ pipes” in the premaxillae. This “pushed” the olfactory region above the eyes as a conspicuous dome which then was modified to form species-specific visual display organs.

Mélano-acanthome

A 87-year-old Caucasian women had a recurrent pigmented tumor on the back. Histologically, the lesion was interpreted as being a melanoacanthoma. It was characterized by a proliferation of unpigmented basaloid cells with aggregates of large prickle cells, forming small horn pearls; furthermore the tumor contained numerous large dendritic cells with large amounts of melanin granules. A short review of the literature is followed by the discussion of the relationship between melanoacanthoma and irritated seborrheic keratosis.

A New Horn Loudspeaker/Microphone for Personal Voice Communication Transceivers

A highly efficient wearable horn loudspeaker/microphone for use with personal voice communication transceivers has been developed. The design incorporates an electrodynamic driver coupled to a small catenoidal horn, packaged to be protected from the environment. The electrical-to-acoustical power conversion efficiency was optimized using a computer program incorporating the parameters of the horn and driver. The prototype transducer provides 105-dB-SPL capability at the ear of the user concentrated at 800–3000 Hz for maximum intelligibility in noise.

Engineering approach to the design of tapered dielectric-rod and horn antennas

The taper profile of optimized dielectric-rod and horn antennas is synthesized as a series of non-interacting planar radiating apertures. The method is semi-empirical, straightforward to apply, enables the dielectric-rod antenna to be satisfactorily optimized and provides a means of evaluating and optimizing a dielectric-horn antenna with variable wall thickness. The optimum profiles are taken as those which smoothly transform the surface-wave power from the launcher to the radiating aperture. The optimization of the dielectric-rod antenna considerably improves the radiation pattern while computations supported by measurements confirm earlier reports that a dielectric-horn can have a higher gain than a metal horn of similar dimension but side-lobe level is seen to be an important issue. Wide flare-angle horns give ideal E-plane patterns at the expense of a high side-lobe level in the H-plane; for small flare angles the dielectric horn gives similar patterns to the tapered rod antenna and thus preserves rotational symmetry. Calculations throughout are restricted to cylindrical geometry but other geometries and variations on the dielectric-horn principles are described. Useful engineering design data have been compiled for both the dielectric-horn and rod antennas and curves are given which determine near-optimum parameters for gains up to about 20 dB which is seen to be a practical operating limit for these surface wave devices. A unified impression of dielectric antennas emerges with the important conclusion that, when optimized, dielectric-rod and horn antennas are in fact competitive with small metal horns for some applications; furthermore the dielectric-horn antenna, used singly or in arrays, is an ideal device for producing a low side-lobe level in the E-plane.

Aperture efficiency enhancement in dielectrically loaded horns

The effect of symmetrically loading a horn aperture with E -plane dielectric slabs is examined both theoretically and experimentally. It is shown that aperture efficiencies of the order of 92-96 percent may be obtained easily and inexpensively. The technique, which was demonstrated experimentally for a small horn aperture, might find application in limited scan arrays.

Morphology of the Reproductive Organs of Dioryctria abietella (Lepidoptera: Pyralidae (Phycitinae))

The reproductive organs and spermatophore of Dioryctria abietella (Denis & Schiffermuller) are similar in general morphological characteristics to those of other Lepidoptera. Eggs were found in the bulla seminalis of many females but did not completely block sperm transmission. The aperture end of the spermatophore has a serrulate surface and exhibits a small horn. These microstructures probably serve to maintain alignment with the opening to the ductus seminalis.

INTRASPECIFIC COMBAT AND THE EVOLUTION OF THE CAPRINI

Among the animals belonging to the mammalian tribe Caprini (sheep and goats), intraspecific conflict between males often takes the form of violent head-to-head butting. This paper correlates differences in fighting behavior among the various genera with the relative development of the neck muscles in each. Fighting style and horn shape are analyzed with reference to the production of torques about the occiput which, if unopposed, would cause violent and injurious rotation of the head. Areas of muscle insertion on the skull were used as the major indicators of muscle size, but dissections were also performed. Further studies of both musculature and behavior are desirable to clarify details which remain obscure. The tribe Caprini is composed of five genera: Hernitragus, tahr; Capra, goats, ibexes; Amnmotragus, Barbary sheep; Pseudois, blue sheep; and Ovis, true sheep-mouflons, argalis, and bighorn. All of these animals possess large, massive horns which are used to deal and receive blows of considerable force. In contrast, their ancestors are believed to have resembled the living Rupicaprini (Pilgrim, 1939; 1947), light-limbed creatures with small horns, quite aptly referred to as goatantelope (McCann, 1956). Rupicaprini are not adapted to withstand, nor do they engage in, the furious head-on collisions of male caprines. Instead, horn-locking and head-to-head pushing occur, along with some body-butting (Couturier, 1938; Geist, 1964; 1966b). Such behavior is considered to be ancestral to the patterns observed in the Caprini (Geist, 1966b). Evolution in the latter group has thus involved alteration of both behavior and morphology, and

Cell size and rate of protein synthesis in ventral horn neurones.

Autoradiographic studies show that small ventral horn neurones synthesize protein at a greater rate per unit area of cytoplasm than do large ones. It is suggested that this is related to the faster rate of firing of the smaller neurones.

Measurement of the Flux Density of CAS A at 4080 Mc/sec.

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Measurement of the Flux Density of CAS A at 4080 Mc/sec. Wilson, R. W. ; Penzias, A. A. ; Hogg, D. C. Abstract The 20- ft-aperture horn reflector at the Crawford Hill Laboratory,, Holmdel, New Jersey, has been used to measure the flux density of Cas A at 4080 Mc/sec. Some forty drift curve observations, each approximately forty minutes in duration, were made on five nights in September and October of 1964. An argon noise tube was used for comparison in each observation. The night to night variation in the results was less than *0.3%. The equivalent effective temperature ~ontributed by the noise tube was measured by four different calibration methods in order to avoid possible systematic errors associated with any single method. The methods employed were: a comparison between the effective temperature of a room temperature resistor and a helium cooled waveguide termination; the direct connection of the noise tube through precision attenuators; the increment in effective temperature produced by a variable attenuator mounted in front of a helium cooled termination; and the increment produced by warming a room temperature termination. The resulting probable error in the calibration is approximately 0.5 %. The radiometer employs a travelling wave maser and a low-loss comparison switch. The system temperature is 190K for zenith orientation. The system gain was found to change less than 1 % per hour during a forty minute observation period, and was thus sufficiently stable to permit all observations to be made with the radiometer operating in an unswitched mode. The gain of the horn-reflector antenna used was obtained by comparison with that of a small standard horn mounted beside its aperture, while the whole assembly was pointed at a helicopter-borne source. The gain of the standard horn was subsequently measured in the laboratory. From these measurements we were able to obtain the gain of the antenna with probable error of approximately 2%. Combining the results obtained above and making a correction for atmospheric absorption based on our measured value of the sky temperature at this frequency (2.30K) we arrive at a flux density of 1.09 X 1()~23 Wm-2 (c/sec)-1 with a total probable error of 2%. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109590 Bibcode: 1965AJ.....70R.150W full text sources ADS |

A note on diffraction theory and polarization

The plane-wave method of calculating the field radiated from an aperture has two forms depending on whether the source is taken as the tangential electric or magnetic field. The Huygens–Kirchhoff method is intermediate between them. There is an apparent inconsistency in the predicted polarization of the distant fields; this is shown to depend on aperture-field terms usually neglected, and measured values of the polarization of the field due to a small horn are given.

Measurement of Gaseous Discharge plasma with Microwave Interferomter

The electron density of the low pies sureplasma was measured with a microwave interferometer bridge and with Langmuir probes simultaneously.At lower electron densities (ca.5×1010/cc), the density obtained from microwave phase shift was lager than that obtained from Langmuir probe possibly due to some inherent error in positive probe measurements.At higher density, however, the agreement between both densities is fairly good if suitable considerations are paid for microwave horn-plasma coupling.Extremely small horn to plasma distance in microwave measurement gives improperly large phase shift or large apparent electron density possibly due to multiple reflections of the incident microwave. Collision frequency of electron was also obtained from microwave attenuation measurements by interferometer.The electron temperature was given from Langmuir probe characteristics by usual method. From these two measurements, collision cross section of Argon for electron was calalated.

白筋及び赤筋線維とこれを支配するα前柱大,小細胞に関する組織学的研究

白筋及び赤筋線維とこれを支配するα前柱大,小細胞に関する組織学的研究

The Compound Diffraction Projector

A public address type driver unit loaded with a reintrant horn on one side of the diaphragm for reproducing the bass frequencies and with a small straight horn on the other side is described. Owing to the small size of the high frequency radiator, considerable improvement in high frequency dispersion is achieved. The high frequency response also is considerably improved over that of a conventional reintrant horn. The two throats of the two horns can both be designed with optimum impedance for the frequency range they are to reproduce.

The effect of flanges on the radiation patterns of small horns

This paper describes the results of experiments carried out on horns having rectangular apertures one dimension of which is of the order of a quarter of a wavelength, the other being of the order of one wavelength or more. The polarization is parallel to the smaller dimension. The paper considers the radiation pattern in a plane normal to the aperture of the horn and perpendicular to the longer sides of the aperture. The results are shown in a graphical scheme which demonstrates the types of radiation pattern resulting when various symmetrical systems of metal flanges are attached to the long sides of the aperture. The scheme shows the effect of variation of two parameters defining the flange system. These parameters are the length of the flanges and the angle contained between their planes. In particular it is shown within what limits the form of the radiation pattern can be regulated by this means, and to what extent it is possible to get patterns of a rectangular shape. It is also shown how various special types of pattern can be generated: e.g. patterns having a pronounced “dip” in the forward direction.

Notes on Rudder Pedal-Force Characteristics

From an analysis of the geometric and airflow parameters that affect the free-floating characteristics of an unstalled rudder during steady sideslips, the effects of these parameters on the rudder pedal-force characteristics have been studied. The results of this study indicate that rudder pedal-force lightenings or reversals are more likely to occur for rudders having large chords or balancing tabs than for rudders having small chords or horn balances. In addition, the results indicate that these undesirable pedalforce characteristics are extremely likely to occur in power-on flight at the sideslip angles at which the vertical tail emerges from the slipstream.

II.—Further Notes on the Mammals of the Eocene of Egypt

The skull of one species (A. Zitteli) of this remarkable ungulate has already been figured by Mr. Beadnell, and also in this Magazine (December, 1903), where its general form is well shown. Details of the structure of the skull and skeleton will be given in the monograph, so that only a few of the more important characters need be referred to here.The pedunculate occipital condyles are very large and prominent; the occipital surface slopes strongly forwards and is bordered by a massive lambdoidal ridge, which on either side (in old animals at least) rises into a prominent backwardly directed boss of bone, almost like a blunt horn. The parietal region of the cranial roof is flat and is at right angles to the side walls of the skull, being sharply marked off from them by well-defined ridges, which form the upper limits of the temporal fossæ. The suture between the parietals is obliterated in the youngest skull examined. The pair of small posterior horns over the orbits are borne exclusively by the frontals, while the great anterior pair seem to be formed entirely by the enormously developed nasals.