Egg production in relation to the results of a long term serological survey of 73 flocks of fowl

Summary Seventy-three flocks of fowl were tested at regular intervals for the presence of precipitins to fowl adenovirus (AV) and infectious bronchitis virus (IBV), haem-agglutinating inhibiting antibodies to BC14 virus, and of agglutinins to Mycoplasma gallisepticum (M.g.) and Mycoplasma synoviae (M.s.). In all the eight flocks affected with Egg Drop Syndrome (EDS '76), egg production problems were associated with increasing numbers of BCI4 virus reactors and AV reactors. In flocks showing production problems other than EDS '76 without any apparent cause, the average percentage of AV reactors increased significantly after the rearing period; this was not true of IBV reactors. BC14 reactors were either absent or present only once, in small numbers and with low titres, during the test period. The average percentage of AV reactors did not increase after the rearing period either in normally producing flocks or in flocks with production problems for which other diseases or dietary errors plausibly accounted for these problems. All this suggests a pathogenic role of AV in production problems. One can conclude from the high percentage of reactors in all groups of flocks that sub-clinical IBV infections are common. The percentage of IBV reactors during the laying period of flocks with EDS '76 was significantly higher than that of normally producing flocks. It is therefore suggested that subclinical IBV infection could be among the factors causing stress, acting as a trigger for EDS '76. All M.g.-infected flocks showed production problems; M.s. infections could not be related to egg production disturbances.     

Occurrence and significance of infectious bronchitis virus variant strains in egg and broiler production in the Netherlands

Despite vaccination against Infectious bronchitis virus (IBV) with the Massachusetts type vaccine viruses H120 and H52 in the Netherlands, an increasing number of properly vaccinated flocks have suffered from the disease since 1978. In the years 1978-1982, the virus was isolated from 162 IBV suspected flocks. Cross-virus-neutralization tests showed that the majority (67 per cent) of these isolates belonged to serotypes other than the Massachusetts type, the Connecticut-, Florida-, Iowa 97-, Iowa 609- and JMK serotype. The majority of these Dutch isolates could be divided into 4 serogroups, called D207, D212, D3128 and D3896. Only a few isolates were not related to these serotypes. A survey of 328 flocks for antibody against these serotypes demonstrated that antibody against one or more of these novel serotypes were present in most of the flocks. Experiments demonstrated that vaccination with the H120 vaccine virus was not able to protect chickens against the adverse effects of a challenge with the novel serotypes.     

Recent development in potato ridging on marine soils in the Netherlands

Summary Dutch farmers have developed various methods of making the elod-free ridges required for modern mechanical potato harvesting. Measurements showed however, that the ridges were smaller than the optimum 500–600 cm², although when the seed-bed was prepared 8–10 cm of loose soil was often present. Contrary to general belief ridging operations decreased rather than increased the amount of loose soil (6.5 cm). This was due to compaction before and during planting; after planting the amount compacted was equal to the amount loosened. Compaction can be reduced by limiting the number of passes over the ground through the use of powered implements for preparing the seed-bed, by combining implements, by making ridges in 1 or 2 operations soon after planting combined with chemical weed control, by using narrow tyres, by removing the loose soil in front of the wheels, and by increasing the distance between rows to 75 cm.

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Zusammenfassung Den holl?ndischen Landwirten ist es gelungen, die Kartoffeld?mme ohne Kluten herzustellen, was für die Ernte mit dem Sammelroder unerl?sslich ist (Abb. 2–6). Aus Messungen geht aber hervor, dass dies auf Kosten der Dammgr?sse geschehen ist, die in erster Linier durch die Anforderungen des Rodens bestimmt wird: m?glichst wenig leicht siebbarer Boden und konzentrierter Knollensitz hoch im Damm. Um das Grünwerden der Knollen und eine Infektion mit Braunf?ule zu verhindern, muss der Damm einen minimalen Umfang, der mit 500–600 cm² angenommen werden kann, aufweisen. Ein Versuch über den Einfluss der Gr?sse eines Dammes auf Wachstum und Lage der Knollen (Abb. 1) hat gezeigt, dass ein Damm von 350 cm² zu klein und ein solcher von 750 cm² nicht besser ist als ein Damm von 550 cm² Feldmessungen haben ergeben, dass trotz einer anf?nglich 8–10 cm dicken Schicht lockeren Bodens nach dem Pflanzen nur · 6,5 cm davon übrigblieb und dass diese Schichtdicke w?hrend des Wachstums ungef?hr konstant blieb. Wahrscheinlich wird also etwa die gleiche Bodenmenge, die von den H?ufelk?rpern gelockert wird also etwa die gleiche Bodenmenge, die von den H?ufelk?rpern gelockert wird, wieder zusammengepresst. Aber auch vor und w?hrend des Auspflanzens geht viel lockerer Boden verloren. Dieser Verlust steigt an, je m?chtiger die lockere Schicht (Abb. 8) und je breiter die Reifen sind (Abb. 7 und 10). Der Verlust lockeren Bodens kann eingeschr?nkt werden, indem beim Auspflanzen und der Saatbettvorbereitung Maschinen mit schmalen Reifen verwendet werden, die zudem den lockeren Boden vor den R?dern beiseite schieben (Abb. 9). Eine weitere Einschr?nkung wird durch das Herabsetzen der Zahl der Arbeitsg?nge errecht, zum Beispiel durch die Kombination von angetribenen oder nicht angetriebenen Ger?ten sowie durch die chemische Unkrautbek?mpfung. Auch die Arbeitsweise beim H?ufeln ist wichtig: wenn man immer durch die gleichen Spuren f?hrt, wird weniger lockerer Boden festgedrückt (Abb. 11). Schliesslich gestattet ein breiterer Reihenabstand, aus der gleichen Menge lockeren Bodens gr?ssere D?mme zu machen (Abb. 12). Dabei werden auch die Furchen breiter, so dass nur ein kleiner Teil der D?mme festgepresst wird. Ein Reihenabstand von 75 cm hat grosse Vorteile: der Weg/ha/Arbeitsgang ist kürzer, die aufzunehmende Bodenmenge/ha beim Roden kleiner, und der Abstand passt in die Normierung von 12,5 cm.

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Résumé Les agriculteurs hollandais ont réussi à réaliser les buttes sans motte indispensables pour la récolte à l’arracheuse-ramasseuse (Fig. 2–6). Mais il résulte de mensurations que ce résultat est obtenu au détriment de la grosseur de la butte, laquelle est déterminée en premier lieu par les exigences de l’arrachanges, le moins possible de terre légère passant au crible, par la formation concentrée et en hauteur des tubercules dans la butte. La prévention du verdissement des tubercules et de l’attaque du mildiou exige un contour minimum dont la surface peut être estiméc à 500–600 cm². Une recherche sur l’influence de la grosseur des buttes sur le développement et l’emplacement des tubercules (Fig. 1) a montré qu’une butte de 350 cm² est trop petite, mais non qu’une butte de 750 cm² est meilleure qu’une de 550 cm². Des mesures effectuées au champ montrent qu’une couverture originelle en sol meuble de 8–10 cm après la plantation s’abaisse à 6.5 cm seulement et que cette épaisseur reste à peu près constante pendant la végétation. Il est aussi vraisemblable que cette méme épaisseur de sol qui est ameublie par les buttages, est de nouveau comprimée. également avant et pendant la plantation, beaucoup de terre meuble se perd. Cette perte augmente avec l’accroissement de la couche meuble (Fig. 8) et de la largeur des bandages (Fig. 7 et 10). La perte de terre meuble peut être limitée en utilisant des bandages étroits pour la plantation et la préparation du lit des plants en même temps en poussant de c?té la terre meuble avant les roues (Fig. 9). Une plus grande économic sera obtenue par la réduction du nombre de pratiques culturales. par exemple en combinant les outlis. motorisés ou non, et par le désherbage chimique. De même la fa?on d’utiliser le buttoir est conséquente: on comprime moins le sol meuble quand on passe toujours par les mêmes sillons (Fig. 11). Finalement une distance accrue entre les lignes permet de réaliser de plus grosses buttes avec la même quantité de sol meuble (Fig. 12), et, en outre, les sillons seront plus larges de sorte qu’un mains grand nombre de buttes seront tassés. L’écartement de 75 cm est fort avantageux. Cet écartement diminue les parcours par hectare pour les fa?ons culturales et la quantité de sol ramassée par hectare lors de l’arrachage, en même temps cette distance se conforme au réglage de 12,5 cm.

     

Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices

Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. Here, we report electrical measurements on indium antimonide nanowires contacted with one normal (gold) and one superconducting (niobium titanium nitride) electrode. Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields on the order of 100 millitesla, we observe bound, midgap states at zero bias voltage. These bound states remain fixed to zero bias, even when magnetic fields and gate voltages are changed over considerable ranges. Our observations support the hypothesis of Majorana fermions in nanowires coupled to superconductors.     

Effect of adenosine infusion on isoflurane MAC in dogs.

Adenosine is a potent analgesic in people and reduces the MAC of halothane in dogs. The purpose of this study was to determine whether adenosine reduces the MAC of isoflurane in dogs. Seven beagles (four males and three females) were anesthetized and randomly assigned to receive adenosine (0.3 mg kg^–1 minute^–1; 6 mL kg^–1 hour^–1, IV) or saline (0.9%, 6 mL kg^–1 hour^–1IV). After an interval of ≥7 days, each dog was reanesthetized and treated with the alternate infusion. Anesthesia was induced and maintained with isoflurane in oxygen. Dogs were intubated and instrumented for measurement of mean systemic arterial blood pressure and airway concentration of isoflurane and end‐tidal partial pressure of carbon dioxide. The MAC for isoflurane was determined using the tail‐clamp technique. Baseline MAC values were 1.25 (1.15, 1.35)% [median (minimum, maximum)] and 1.25 (1.05, 1.45)% before the saline and adenosine treatments, respectively. After 2 hours of infusion with saline or adenosine, MAC values were not different (p = 0.156) and were 1.25 (0.95, 1.35)% and 1.05 (1.00, 1.25)%, respectively. Two hours following the end of each infusion, the MAC values for saline and adenosine treatment groups differed significantly (p = 0.015), but by no more than the normal variation inherent in this study, and were 1.15 (1.15, 1.35)% and 1.05 (1.05, 1.25)%, respectively. Mean arterial blood pressure was 93 (74, 123) mm Hg for saline treated dogs and 67 (52, 72) mm Hg (p = 0.008) during adenosine infusion. End‐tidal carbon dioxide was not different between the two treatment groups. We conclude that adenosine administered at 0.3 mg kg^–1 minute^–1had no effect on isoflurane MAC in dogs, but decreased mean arterial blood pressure.     

兔病毒性出血症与大肠杆菌混合感染的诊治

以发生于本市的一起兔病毒性出血症与大肠杆菌病混合感染的病例为题材，从发病情况、临床症状、病变、实验室检查、防治等几个方面作了详尽的阐述，为临床上治疗该病提供参考依据。     

The immune response of the chick following viral vaccinations and immunization with sheep red blood cells

The effects of viral vaccinations and immunization with sheep red blood cells (SRBC) on the humoral response of pullets were investigated. Pullets were vaccinated with Marek's disease virus, Newcastle disease virus (NDV), infectious bronchitis virus (IBV), and infectious bursal disease virus at appropriate ages used in commercial practice. At seven weeks, the pullets were intramuscularly immunized with SRBC. NDV and IBV antibodies were detected by hemagglutination-inhibition tests. Hemagglutination (HA) titers were established against SRBC. IBV antibody titers were not affected by vaccination or by immunization with SRBC. NDV antibody titers were significantly increased by vaccination and by immunization with SRBC. The SRBC agglutinin response was also positively affected by vaccination. The HA titer increase consisted of a rise in 2-mercaptoethanol (2-ME)-sensitive antibodies and a fall in 2-ME-resistant antibodies.     

Tunable supercurrent through semiconductor nanowires

Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.     

The kondo effect in the unitary limit

We observe a strong Kondo effect in a semiconductor quantum dot when a small magnetic field is applied. The Coulomb blockade for electron tunneling is overcome completely by the Kondo effect, and the conductance reaches the unitary limit value. We compare the experimental Kondo temperature with the theoretical predictions for the spin- 12 Anderson impurity model. Excellent agreement is found throughout the Kondo regime. Phase coherence is preserved when a Kondo quantum dot is included in one of the arms of an Aharonov-Bohm ring structure, and the phase behavior differs from previous results on a non-Kondo dot.