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.     

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.     

Detection of quantum noise from an electrically driven two-level system

The electrical noise of mesoscopic devices can be strongly influenced by the quantum motion of electrons. To probe this effect, we have measured the current fluctuations at high frequency (5 to 90 gigahertz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device, we can measure the high-frequency, nonsymmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.