Ion probe technique for the study of gallium diffusion in silicon nitride films

The penetration of Ga in films of amorphous Si₃N₄ about 2000 Å thick on Si substrates has been studied. The films were produced by pyrolysis. Diffusion profiles were obtained by surface exposure to Ga vapor, and the implantation profiles by ion bombardment in an isotope separator. Evaluation of the profiles was effected by means of sputtering in a secondary ion microanalyzer. For depth calibration, ion yield profiles of ⁶⁹Ga⁺ of ⁷¹Ga⁺ were compared with the profiles of ³⁰Si⁺, ⁷⁰(Si₂N⁺, SiN⁺₃) and ⁷²Si₂O⁺. The integration of implantation peaks furnished a means of obtaining absolute values of Ga concentrations from the secondary ion intensities. Hence the surface concentration of vapor-deposited Ga at 1100°C was assessed to be of the order of 8 × 10²⁰ atoms cm^-3. The diffusion coefficient of Ga in Si₃N₄ at 1100°C was found to be about 5 × 10^-17 cm² s^-1. The method, which combines sputtering and mass spectrometry, appears to be applicable for measuring diffusion coefficients in this system down to about 3 × 10^-18 cm² s^-1.     

Recovery of polluted lakes. a swedish research program on the effects of advanced waste water treatment and sewage diversion

In order to elucidate the effects of the effluents from advanced wastewater treatment plants for phosphorus removal, the National Swedish Environment Protection Board during 1972 started a program for analysing the conditions in a number of different recipient lakes. This study of recovery of polluted lakes also includes some recipient lakes from which sewage effluent will be completely diverted. This paper presents the program, some new methods used and the treatment plants and recipient lakes involved. The project. including 18 lakes and 15 sewage treatment plants, is running in cooperation with 13 Provincial Governments and 16 Municipalities. The efficiency of the sewage treatment plants, is continuously monitored by a new method called Minitest, and the nutrient loadings from these plants as well as from other sources are calculated.As the water quality of many recipient lakes showed great variations during the vegetation period (see Fig. 2), a need for a frequent sampling exists in these lakes.In order to simplify the sampling procedure sampling on the shore (after pumping water from the sampling point) has been introduced. Data obtained after analysing samples taken from a boat and samples from the same area taken on the shore after pumping through a 600 m plastic tube showed good agreement (see Table 2).The lake water samples are preserved by freezing, Analyses after rapid thawing showed that this method can be used also when determining from cell material easily leaking ions such as PO₄, NO₃ etc. (see Tables 3 and 4).The sewage treatment plants, the recipient lakes and some background data are presented in Tables 5 and 6. The water quality of the lakes is illustrated with the correlation between chlorophyll A and suspended solids (Fig. 3). The correlation coefficient = + 0–88. The first sign of lake recovery has been observed after an 85 per cent reduction of the waste phosphorus load. Post-precipitation (A1-sulphate) decreased the yearly load from 2000 kg P to 300 kg, which gave a 50 per cent reduction of the P content of the recipient water. Also the chlorophyll values decreased (Table 7).The role of nitrogen and phosphorus as algal growth limiting nutrients has been studied by using an algal assay procedure. N limited the growth of Selenastrum capricornutum in of the samples. In filtered lake water P was the growth limiting nutrient at total-P values below 0–05 mg 1⁻¹. Above 0·1 mg P 1⁻¹ N played the principal role. Between these values the growth was primarily limited by P or N or chelating agents (Fig. 4).     

Immune modulatory effects of immunoglobulins on cell-mediated immune responses in vitro

Intravenous Immunoglobulin (IVIG) at a concentration of 5 mg/ml, significantly inhibited mitogenic responses to phytohaemagglutinin (PHA), concanavalin A (conA) and pokeweed mitogen (PWM) by peripheral blood cells from healthy donors. No difference in inhibition by IVIG was seen when stimulating different T-lymphocyte cell subsets. Inhibition by IVIG was dose-dependent. An increased response was observed when IVIG was added more than 12 h after PHA compared to adding 1 h before [P = 0.05]. Intravenous immunoglobulin added to mixed lymphocyte cultures (MLC), reduced the median response by more than 60% (range 14-89%; P = 0.03) and almost completely abrogated the lymphocyte response to Staphylococcus aureus protein A (SPA), whose median inhibition was 94% (range 90-99%; P = 0.02). When comparing 12 different commercial IVIG preparations at a concentration of 2.5 mg/ml, the median inhibition of the PHA stimulation ranged from 4% to 35% and the MLC response from 0% to 66%. In the presence of IVIG the lymphocyte response to different herpes virus antigens was reduced by > 50%. No difference in inhibitory effect was seen when comparing IVIG and cytomegalovirus (CMV) hyper Ig, but CMV negative Ig resulted in lower inhibition [P = 0.05]. Three out of five IgG preparations (2.5 mg/ml) made from single donors inhibited PHA stimulation significantly more than commercial IVIG [P < 0.05]. Mean inhibition was 61% compared to 35%. Inhibition by pooled IgG from five donors was 56%. F(ab')2 fragments of IVIG inhibited the MLC response by more than 50% (range 34-75%), SPA stimulation by 97% (83-104%) and PHA stimulation by more than 30% (26-37%). One of two Fc preparations tested had an inhibitory effect, but the inhibition was less than that obtained with the F(ab')2 fragments [P = 0.04]. These results further strengthen the notion that IVIG exerts its immune modulatory effect by binding to leukocyte surface receptors. A clear inhibition was obtained with concentrations corresponding to the serum levels obtained when IVIG is given 250-500 mg/kg bodyweight. F(ab')2 fragments have the same inhibitory effect as intact IgG molecules but the role of Fc fragments still remains unclear. Differences in the immunosuppressive effect of various IVIG preparations may be associated with the method of preparation.     

A Fully Abstract Semantics for Concurrent Constraint Programming

A compositional and fully abstract semantics for concurrent constraint programming is developed. It is the first fully abstract semantics which takes into account both non-determinism, infinite computations, and fairness. We present a simple concurrent constraint programming language, whose semantics is given by a set of reduction rules augmented with fairness requirements. In the fully abstract semantics we consider two aspects of a trace, viz. the function computed by the trace (the functionality) and the set of input and output data (the limit of the trace). We then derive the fully abstract semantics from the set of traces using a closure operation. We give two proofs of full abstraction; the first relies on the use of a syntactically infinite context. The second proof requires only a finite context, but assumes as input a representation of the function to be computed by the context. Finally, we examine the algebraic properties of the programming language with respect to the fully abstract semantics. It turns out that the non-deterministic selection operation can be defined using operations derived from parallel composition and the usual set-theoretic operations on sets of traces.     

Biological activity and brain actions of recombinant rat interleukin-1alpha and interleukin-1beta

An HMQC experiment is proposed, dubbed FHMQC, where water flip-back is achieved by a single water-selective pulse preceding the basic HMQC pulse sequence. The scheme is demonstrated with a 15N,1H-HMQC spectrum of uniformly 15N/2H-labelled S. aureus DNA gyrase B with a molecular weight of 45 kDa for the unlabelled protein. The sensitivity of the experiment is improved compared to that of an FHSQC spectrum. It is further shown that the original FHSQC experiment can be shortened by the use of bipolar gradients. Relaxation times of different 15N magnetizations and coherences were measured. The new FHMQC scheme is implemented in 3D NOESY-15N-HMQC and 3D 15N-HMQC-NOESY-15N-HMQC pulse sequences which are demonstrated with a 24 kDa fragment of uniformly 15N/13C/2H-labelled S. aureus DNA gyrase B.     

Frequency distributions of water quality variables : Relationships between mean and maximum values

Frequency distributions of water quality variables have been analysed by using about 950 samples from 25 meso- to hypertrophic lakes. By expressing all values as relative to their means, data from all the lakes could be pooled to datasets based on about 950 values for each variable. The distributions of COD, conductivity, pH and colour were symmetrical with very high frequencies around 100% of the mean. The variables of total-N, total-P, suspended solids and Secchi disk transparency followed more skew distributions, while turbidity, chlorophyll a and MRP were markedly skewed. The inorganic nitrogen fractions had their highest frequency at or just above zero percent of the mean.Three probability density functions (pdf) namely beta, gamma and log normal distributions were fitted to the pooled data. There were two variables, colour and conductivity, which did not fit to any of the pdf's but for the rest the null hypothesis could not be rejected at the 99.5% level. Frequency distributions for each lake demonstrated that for most variables one or two lakes showed distributions deviating from the pooled data pdf. There were no discernible trends among lakes and the number of rejections seemed to be randomly distributed. The study is inconclusive but does not reject the approach of using frequency distributions of relative values when only the mean is known. Agreement between expected maxima and those observed by other investigators indicate that the log normal distributions estimated here might be generally applicable as a rule of thumb on what the maximum will be in relation to the mean. The results of this study also indicate that the frequency distributions are similar for a large variety of water quality in many lakes. This information is of great interest for water management as good approximation of maximum values might be achieved if the means are known.