Short Horn Research Articles

Application of optical ray technique to the design of short microwave horn antennas with low side lobe levels

Optical ray theory is used to design a phase-corrected microwave horn antenna of shortlength which produces a tapered aperture amplitude distribution in the E-plane. The basis of the design is the creation of a region where the effective refractive index varies with hyperbolic secant (HYSEC) form in a direction normal to the horn axis. In a practical realisation this effective refractive index distribution is achieved in both smooth and stepped form by varying the plate separation of the planar waveguide supporting a TE01 mode. Good agreement is found between predicted and experimentally determined aperture and far-field distributions. Finally, the study is extended to the design of a novel antenna incorporating dielectric loading which, in theory, allows for operation at even shorter horn lengths.

Balkanski narodni instrumenti

Balkanski narodni instrumenti

ESTIMATION OF GENETIC TRENDS FOR CANADIAN STATION-TESTED BEEF BULLS

Data collected from Canadian central test stations were used to obtain estimates of genetic progress for test station average daily gain (ADG-T), height at hooks (HH), ultrasonically measured backfat thickness midway between the 11th and 12th ribs (FAT) and scrotal circumference (SC). Where possible, records for preweaning average daily gain (ADG-W) from the Federal-Provincial Herd Record of Performance program were obtained for tested bulls. Estimated breeding values were regressed on year of birth to obtain estimates of genetic trend for each trait, for the six principal breeds enrolled in the testing program: Aberdeen Angus (AA), Charolais (CH), Hereford (HE), Limousin (LM), Shorthorn (SH) and Simmental (SM). Estimated trends were generally significant with the exception of those for the LM breed, and the trait of SC. For FAT, trends were generally positive for the exotic breeds, and negative for the British breeds. Significant positive trends were observed for HH, ADG-W and ADG-T for most breeds. Examples of estimated genetic trends, for the HE breed, were 0.0022 kg d−1 yr−1, 0.0023 kg d−1 yr−1, 0.090 cm yr−1 (NS), − 0.029 mm yr−1, and 0.009 cm yr−1 (NS), respectively, for ADG-W, ADG-T, HH, FAT and SC (NS = not significant). Most estimated trends were low, in the order of 0.1 to 0.5% of population mean per year. Key words: Genetic trend, central test stations, beef bulls

Antiproton Production and Collection for the CERN Antiproton Accumulator

Antiprotons are produced for the CERN Antiproton Accumulator (AA) by focusing 26 GeV/c protons onto a 3 mm diameter, 11 cm long copper wire. Negatively charged particles with momenta about 3.5 GeV/c are focused by a short focal length coaxial horn and transported to the AA by a normal quadrupole focusing channel. The yield of antiprotons was found to be considerably less than anticipated (factor about 2) and the reason is presumed to be the assumption of too large a production cross-section in the original machine design proposal. Studies involving new horn design, introduction of an axial current e 150 kA) along the target and use of lithium lenses as an alternative to the magnetic horn are under way. Some preliminary measurements involving some of these techniques have been made, both to confirm the validity of calculations and to test the feasibility of building targets and focusing systems to withstand the mechanical forces and heat load due to the proton beam and the high pulsed currents.

Ultrastructure of a specialized thrust-sensitive, insect mechanoreceptor: stimulus-transmitting structures and sensory apparatus in the rostral horns of Notiophilus biguttatus.

1. High-speed film recordings show that larvae of the beetle Notiophilus biguttatus, when attacking a prey, close their mandibles once the prey has been touched by two paired conical processes of the clypeolabrum (rostral horns). 2. In the third larval stage, the horns of one pair are about 140 μm long, those of the other pair about 50 μm. In each horn, a mechanosensitive hair is inserted into the distal portion. In the long horns, the hair is 35 μm long, in the short horns only 3.5 μm. Only the tips of the hairs are visible externally. Their shafts are enclosed within a cuticular collar, which makes up the walls of the horns. The cleft between the hair shaft and the surrounding collar is only about 0.1–0.2 μm wide. A sensory receptor cell is connected to each hair, which is characterized as a mechanoreceptor by the presence of a tubular body. 3. From structural characteristics, it can be deduced that the sensory receptor cell is stimulated not by axial displacement of the hair but rather by tilting movements, which lead to a transverse compression of the dendrite. 4. Geometric determinations from longitudinal sections demonstrate that hair-shaft deflections are limited to only about 20 min of arc in the long horns. The short horn sensory hairs can be deflected to a maximum of about 2°. The maximal displacement of the cuticular lever arm at the level of the tubular body and the values calculated for movement per degree of hair-shaft deflection lie within the normal range for mechanosensitive hairs (Table 1). 5. Considering their structural peculiarities, the long-horn receptors seem to be thrust-sensitive and to react to ramp stimuli of 20 min of arc in an all-or-nothing fashion. The short-horn receptors could react to graded hair-shaft deflections. 6. The main structural specialization of the rostral horn mechanoreceptors in evolution is the elongation of the socket region to form a cuticular collar around the sensory hair.

The Performance of a New Direct Contact Applicator for Microwave Diathermy

A direct contact applicator, specifically designed for microwave diathermy at the Industrial, Scientific Medical (ISM) frequency of 2.45 GHz was evaluated by studying near-field patterns in free space, thermographic heating patterns in phantoms of simulated fat and muscle tissue, and associated leakage radiation. The main features are a circular waveguide with a short conical flare horn output section surrounded by an annular choke and two sets of dual posts to generate far-field circular polarization. The significant near field components of the therapeutic beam are in a transverse plane, parallel to the aperture. Heating patterns on the exposed surface of muscle phantoms and inside fat-muscle phantoms are spatially similar and relatively uniform. The leakage level is 0.8 mW/cm/sup 2/ per 100 W of forward power for direct contact and 4 mW/cm/sup 2/ per 100 W of forward power for a 1-cm air gap between aperture and planar phantoms. The uncertainty of these leakage measurements is /spl plusmn/2 dB. This investigation demonstrates the technical feasibility of a safe and effective direct contact microwave diathermy applicator operating at 2.45 GHz. The applicator is a viable candidate for hyperthermia appllications.

Sensitization and habituation of dorsal horn cells in cats.

1. Extracellular recordings were obtained from spinal dorsal horn cells in acutely spinalized cats anaesthetized with sodium pentobarbitone. The dorsal horn cells studied responded to ipsilateral tactile stimulation of the central pad of the hind foot. Eleven short latency dorsal horn cells driven by electrical stimulation of the foot pad were studied intensively; these short latency dorsal horn cells all discharged within 1.5 msec of the arrival of an afferent volley at the dorsal root entry zone. Electrode tip sites were histologically verified to lie near the medial border of the dorsal horn in the seventh lumbar segment, in Rexed's laminae III and IV. 2. Electrical stimulation of the foot pad not only activated the dorsal horn cells studied, but also produced a reflex discharge which was monitored by recording from the ipsilateral first sacral ventral root, which had been sectioned intradurally and mounted on bipolar recording electrodes. Repeated stimulation of the foot pad at moderate intensities and frequencies (e.g. three times threshold for the ventral root response at 5 Hz) typically produced a transitory increase in the magnitude of the reflex discharge (sensitization) followed by a marked waning of the reflex magnitude (habituation). Within a few minutes following cessation of stimulation, the reflex magnitude returned to its prestimulation value. During repeated bouts of five hundred stimuli each, at frequencies from 1.0 to 10.0 Hz, and intensities 1.5-10.0 times reflex threshold, the firing pattern of a short latency dorsal horn cell was monitored along with the magnitude of the ventral root response. Changes in response patterns of the dorsal horn cells were compared to those of the reflex discharges. 3. The short latency dorsal horn cells fell into two distinct patterns of response. The firing pattern of six dorsal horn cells paralleled the response pattern of the reflex discharge; when the reflex increased in magnitude, each of these dorsal horn cells increased in number of responses per stimulus; when the reflex discharge decreased in magnitude, each of these dorsal horn cells decreased the number of responses per stimulus. These dorsal horn cells were characterized by the following: intermediate thresholds to tactile stimulation, comparable to that of the reflex discharge itself; relatively low numbers of responses per stimulus (mean: 1.3/stimulus); low spontaneous activity rates (once per 10 sec or less). 4. The firing patterns of the other class of short latency dorsal horn cells did not parallel the response pattern of the reflex discharge; these showed only a rather rapid, though moderate, decrease in responses per stimulus over the entire range of intensities and frequencies tested. These five dorsal horn cells were characterized by the following: thresholds of tactile stimulation considerably below that of the reflex discharge itself; bursts of responses following each stimulation (mean: 7...

Near-field broadside coupling between two H-plane sectoral horns

The near-field broadside coupling between a pair of two-dimensional H-plane sectoral horns is derived using the method of overlapping regions in conjunction with Schwarz's procedure to solve the resulting integral equations by numerical iterations as well as the generalized scattering matrix technique. The primary advantage of the method is that it allows an arbitrary initial assumption of the aperture field distribution and reasonably corrects it in order to take into account the multiple scattering effects. It is shown that only a few iterations are required for typical coupling geometry and that the number of iterations and the convergence of the series' computations are improved for shorter horns and closer separation distances. Graphical results for the aperture field distributions for specific geometries are presented.

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.

Design of short e-plane sectoral horns

A method combining the `generalised telegraphist's equations´ with a mode-matching technique is proposed well suited for the calculation of short horn antennas. Curves are given for the optimum flare angle, gain and reflection coefficient of a plane sectoral horn excited in the TEM mode. It is shown, that for short horns the aperture-throat interactions cannot be neglected.

Morphological variations in Ceratium egyptiacum in different natural habitats

A statistical study on the morphological variations of the dinoflagellate species Ceratium egyptiacum Halim was carried out in three distinct natural environments: The Red Sea, the Bitter Lake (Suez Canal), and the Mediterranean waters at Port Said, Egypt. Significant seasonal and regional variations were found in the parameters studied (length of the cell, transdiameter, length of the apical and right antapical horns). These variations are mostly attributable to variations in both the temperature and salinity of the environment. On the whole, it was found that high temperature tends to produce longer horns and smaller thecae, while low temperature produces larger cells with shorter horns; high salinity tends to intensify these effects. The right antapical horn is the most labile horn, and the transdiameter of the cell is the most stable parameter. It is suggested that these variations are directly related to flotation. The effect of the Bitter Lake as a unique natural environment (salinity 47‰) on plankton organisms has been evaluated; it is a function of time. The systematic consequences of the structural variations have been discussed; they are probably not genetic, and the resulting types are mere ecotypes of no immediate systematic consequence.

THE LEUKOCYTIC RESPONSE TO AN INTRAUTERINE FOREIGN BODY IN THE RABBIT

39 New Zealand white female rabbits and 15 Sprague-Dawley female rat s were used to determine if a relatively small silicone plastic intrauterine foreign body (IUFB) would produce an incomplete antifertility action and to correlate the number of inflammatory cells in the uterine fluid with the presence or absence of pregnancy in the IUFB uterine horn. Rabbits were bred 5 days after devices were inserted and rats 3 days after. Both species were sacrificed 10 days postcoitus. Corpora lutea were counted uterine horns flushed implantations noted and cells enumerated. Of 39 rabbits 33 had corpora lutea in both ovaries and each had 1 or more implantation sites. 6 were classified was nonpregnant due to mating failure. There was a significant difference in fertility rates between the 33 control horns and the 33 IUFB horns (.86 vs. .5 p less than .001). There was also a significant difference in the mean number of leukocytes in the ut erine flushings of the IUFB side compared to the control side (32.6 vs. 3/cu. mm p less than .001). As the number of leukocytes increased in the IUFB horns the fertility rate diminished. The implantation site size was significantly smaller in the IUFB horn (p less than .001). Those animals with longer uterine horns containing IUFBs also had more implantation sites than those with shorter horns. The maximum infertility effect of the IUFB was exerted in the immediate vicinity of the device. Also sections of endometrium taken at a distance from the IUFB showed fewer polymorephonuclear leukocytes than in areas nearer to the IUFB. No evidence of resorption of embryos or placentas was found in any horns. In rats the IUFBs almost completely prevented pregnancy in those horns where placed; in the control horns pregnancies were of no rmal frequency (p less than .001). There was a significant difference i n the number of leukocytes in uterine flushings in IUFB and control rats (643 vs. 11 leukocytes/cu. mm p less than .001). When pregnancies occurred in the rabbit IUFB uterine horn the number and size of implantations were found to be inversely proportional to the total number of leukocytes present. The distance of implantation sites from the IUFB was directly proportional to the quantity of leukocytes.

Seasonal changes in the ejaculate characteristics of Angoni (short horn Zebu) bulls.

The Angoni cattle are the predominant short horn Zebu type found in the Eastern Province of Zambia and in Malawi, and are related to the East African Zebu (Mason and Maule, 1960). In Zambia the altitude varies from 3,000 to 5,000 feet; there are three recognizable seasons—rainy, cold and hot-dry. Although the duration of each season varies, usually the rainy season lasts from mid-November to mid-March (mean rainfall 28 to 70 inches, relative humidity (RH) 89%, and mean temperature 80.7 F), the cold season from mid-March to mid-July (mean temperature 48 F and RH 59%) and the hot-dry season from mid-July to mid-November (mean temperature 83 F and RH 45%). It is common practice in commercial beef production in this part of Africa to confine the breeding of cows to the 2-month period following Christmas which coincides with the rainy season and which appears to approximate the peak breeding season under natural conditions if bulls are run with the cows all year round.

Puberty and related phenomena in Angoni (short horn Zebu) bulls

Puberty and related phenomena in Angoni (short horn Zebu) bulls

Ejaculation and ejaculate characteristics of Angoni (Short Horn Zebu) bulls.

Ejaculation and ejaculate characteristics of Angoni (Short Horn Zebu) bulls.

The Leukocytic Response to an Intrauterine Foreign Body in the Rabbit

39 New Zealand white female rabbits and 15 Sprague-Dawley female rat s were used to determine if a relatively small silicone plastic intrauterine foreign body (IUFB) would produce an incomplete antifertility action and to correlate the number of inflammatory cells in the uterine fluid with the presence or absence of pregnancy in the IUFB uterine horn. Rabbits were bred 5 days after devices were inserted and rats 3 days after. Both species were sacrificed 10 days postcoitus. Corpora lutea were counted uterine horns flushed implantations noted and cells enumerated. Of 39 rabbits 33 had corpora lutea in both ovaries and each had 1 or more implantation sites. 6 were classified was nonpregnant due to mating failure. There was a significant difference in fertility rates between the 33 control horns and the 33 IUFB horns (.86 vs. .5 p less than .001). There was also a significant difference in the mean number of leukocytes in the ut erine flushings of the IUFB side compared to the control side (32.6 vs. 3/cu. mm p less than .001). As the number of leukocytes increased in the IUFB horns the fertility rate diminished. The implantation site size was significantly smaller in the IUFB horn (p less than .001). Those animals with longer uterine horns containing IUFBs also had more implantation sites than those with shorter horns. The maximum infertility effect of the IUFB was exerted in the immediate vicinity of the device. Also sections of endometrium taken at a distance from the IUFB showed fewer polymorephonuclear leukocytes than in areas nearer to the IUFB. No evidence of resorption of embryos or placentas was found in any horns. In rats the IUFBs almost completely prevented pregnancy in those horns where placed; in the control horns pregnancies were of no rmal frequency (p less than .001). There was a significant difference i n the number of leukocytes in uterine flushings in IUFB and control rats (643 vs. 11 leukocytes/cu. mm p less than .001). When pregnancies occurred in the rabbit IUFB uterine horn the number and size of implantations were found to be inversely proportional to the total number of leukocytes present. The distance of implantation sites from the IUFB was directly proportional to the quantity of leukocytes.

Theatre-Type Loudspeaker Systems

The use of loudspeakers for theatres and auditorium sound reinforcement is reviewed starting with designs used for the first sound motion pictures 40 years ago. The first standardized two-way loudspeaker system application began in 1936, followed by improvements in 1945. In 1969, a theatre-type two-way system was designed to incorporate the experience of their use to date. The objectives of the design were: (1) extended frequency range (30 Hz–12 kHz); (2) more uniform distribution (sectoral horn vs multicell horn); (3) lower distortion (shorter horn and larger throat); and (4) increased reliability (use of improved material over temperature range).

Application of the Acoustically Terminated Tube for the Measurement of Horn-Loudspeaker-Driver Characteristics

The application and limitations of the acoustically terminated small-diameter tube and calibrated pressure microphone to the measurement of horn-loudspeaker-driver characteristics are discussed. Terminated-tube measurement data obtained from a loudspeaker-horn driver are presented showing acoustic power output as a function of frequency, harmonic distortion as a function of frequency, intermodulation distortion as a function of frequency and acoustic power output, and one-third octave band pink-noise distortion. Measurement data taken from a horn driver coupled to a short horn operating in an anechoic environment as well as a diffuse field environment will be presented and correlated with the data obtained from terminated tube-measurements of the horn driver alone. This work was performed as a result of the proposals from Writing Groups S1-47 and IEC TC 29B. The one-third-octave pink-noise distortion test was proposed by the Russian delegate to TC 29B, Morris G. Belkin.

Spontaneous chromosome mutations in Truxaline grasshoppers.

Three distinct mutant conditions are described in single male individuals from three species of short horn grasshopper. Of these, one is an entire germ line mutant of Myrmeleotettix maculatus, heterozygous for a centric fusion between single M4 and M5 telocentric chromosomes. In contrast, the remaining two mutants are present in mosaic form. One is heterozygous for an L1-M4 interchange in Omocestus viridulus, the other tetrasomic for the M4 chromosome in Chorthippus parallelus which in addition is characterised by the inclusion of a supernumerary heterochromatic segment on one S8 homologue. Centric fusion in Myrmehotettix maculatus has neither disturbed the chiasma potential of the elements constituting the fusion multiple nor, has it apparently influenced the production of balanced gametes. The pattern of chiasma formation in the L1-M4 interchange multiple lends support to the contention that the process of chiasma formation originates near the distal end of chromosome arms in Omocestus viridulus. There is no interaction between the two mutant conditions of tetrasomy and the presence of supernumerary segments in Chorthippus parallelus. Moreover, because of the precocious nature of two of the four M4 homologues there is little tendency to form multivalents. The two M4 bivalents share a similar mean chiasma frequency.

Measurement of Ultrasonic Intensity in Liquids by Acoustic Measurements in Overlying Air

Direct probing of ultrasonic fields in liquid systems of interest to industry are difficult for two reasons: (a) modification of acoustic field by cavitation at probe surface, (b) physical or chemical interaction between probe and medium (e.g., hot molten metal). The sound-pressure level in an air space above the liquid provides a direct but noninteracting measure of the particle velocity of the liquid surface. For an extended sound field in linear media, the ratio of the SPL in the air to that in the liquid has been calculated to be A(Zl/Za), where Z is the acoustic impedance of the medium and A is a constant in the range 0.8–1.4, depending on the field geometry. A probe-tube condenser suitable for such air measurements has been constructed. The dependence of the SPL ratio on Zl has been tested, using a narrow liquid column (water or mercury) coupled to a short air-filled horn. The dependence on field geometry has been tested by measurements also with an ultrasonic cleaning bath.