Differential membrane-based nanocalorimeter for high-resolution measurements of low-temperature specific heat.

A differential, membrane-based nanocalorimeter for general specific heat studies of very small samples, ranging from 0.5 mg to sub-µg in mass, is described. The calorimeter operates over the temperature range from above room temperature down to 0.5 K. It consists of a pair of cells, each of which is a stack of heaters and thermometer in the center of a silicon nitride membrane, in total giving a background heat capacity less than 100 nJ/K at 300 K, decreasing to 10 pJ/K at 1 K. The device has several distinctive features: (i) The resistive thermometer, made of a Ge(1 - x)Au(x) alloy, displays a high dimensionless sensitivity ∣dlnR∕dlnT∣ ≳ 1 over the entire temperature range. (ii) The sample is placed in direct contact with the thermometer, which is allowed to self-heat. The thermometer can thus be operated at high dc current to increase the resolution. (iii) Data are acquired with a set of eight synchronized lock-in amplifiers measuring dc, 1st and 2nd harmonic signals of heaters and thermometer. This gives high resolution and allows continuous output adjustments without additional noise. (iv) Absolute accuracy is achieved via a variable-frequency-fixed-phase technique in which the measurement frequency is automatically adjusted during the measurements to account for the temperature variation of the sample heat capacity and the device thermal conductance. The performance of the calorimeter is illustrated by studying the heat capacity of a small Au sample and the specific heat of a 2.6 µg piece of superconducting Pb in various magnetic fields.

A serological survey of bovine herpesvirus-1 infection in selected dairy herds in northern and central Italy.

Serum samples from a total of 6979 dairy cattle from 55 herds in northern Italy (51 herds) and central Italy (4 herds), were examined by the serum neutralization test for the presence of antibody to bovine herpesvirus-1 (BHV-1). It was found that 84.31% of the farms selected in northern Italy and all the farms from central Italy had seropositive animals at titers of 1:4 or higher. The prevalence of infection was essentially the same among the cattle populations of the two selected areas of the country, being of 34.99% in the north and of 38.65% in central regions. A comparison of the data from the present study with those obtained in a serological survey conducted in Italy in 1966, shows that the rate of seropositive cattle to BHV-1 has increased by about 5.0% in the last 30 years.

A non-specific defence inducer in preventing clinical signs of infectious bovine rhinotracheitis in calves.

One calf was infected with bovine herpesvirus-1 (BHV-1) and mixed with five other calves, of which one had been vaccinated with a BHV-1 modified live vaccine one month earlier. The other four calves were vaccinated at the time the experimentally infected calf developed the first signs of the disease (fever, depression, nasal discharge), i.e. on post infection day (PID) 2. In addition to the vaccine, two of the four PID 2 vaccinated calves also received a non-specific defence (NSD) inducer (Baypamun, Bayer AG) at the same time as the vaccine. The calf that was vaccinated 1 month before the start of the experiment, as expected, did not show any signs of the disease. Of the remaining four, the two vaccine-only calves experienced a classical form of infectious bovine rhinotracheitis. However, the two calves that had also received the NSD inducer remained generally healthy during the entire observation period of 30 days. It was speculated that the use of a NSD inducer once an outbreak of a respiratory disease has started on a farm could be of significant help in an emergency in reducing the clinical manifestations in those animals that may subsequently be infected.

The use of a non-specific defence mechanism inducer in calves exposed to bovine herpesvirus-1 infection: preliminary trials.

The efficacy of an immunomodulator, the Baypamun (Bayer AG), was tested in calves which were subsequently exposed to bovine herpesvirus-1 (BHV-1) infection. Two groups of calves, of 8 animals each, were used for two trials. In one trial, 4 calves were treated with the immunomodulator and the remaining 4 were left as untreated controls. Two hours after the first injection of Baypamun, all calves, i.e. the treated and the untreated ones, were challenged with BHV-1. Comparing them to the untreated controls, the calves which were given the immunomodulator developed milder signs of the disease and shed a significantly lower concentration of virus. In the second experiment, 4 calves were given Baypamun and 4 calves were not, as above, but they were not inoculated with BHV-1; however, they were housed together with the calves of the former group (experimentally infected with BHV-1). The 8 calves all became infected but those that had been treated with Baypamun did not show any clinical signs of the disease, whereas the untreated calves underwent a clinical response which was considered to be typical of BHV-1 respiratory infection, as usually seen under natural conditions. In this case the shedding of virus by the calves treated with the immunomodulator also underwent a significant reduction.