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There is increasing concern over the possibility of adverse cumulative watershed effects from intensive forest management. It is impractical to address many aspects of the problem experimentally because to do so would require studying large watersheds for 100 yr or more. One such aspect is the long-term effect of forest management strategies on erosion and sedimentation and the resultant damage to fish habitat. Is dispersing activities in time and space an effective way to minimize cumulative sedimentation effects? To address this problem, Monte Carlo simulations were conducted on four hypothetical 10 000-ha fifth-order forested watersheds: one watershed was left undisturbed, one was completely clearcut and roaded in 10 yr, with cutting starting at the head of the watershed and progressing toward the mouth, another was cut at the rate of 1% each year beginning at the watershed’s mouth and progressing upstream, and another was cut at a rate of 1% each year, with individual cut areas being widely dispersed throughout the watershed. These cutting patterns were repeated in succeeding centuries, rebuilding one-third of the road network every 100 yr. The parameters governing the simulations were based on recent data from coastal Oregon and northwestern California, Mass wasting, the most important source of sediment in that environment, was the only hillslope process modeled. The simulation results suggest that (i) the greatest differences between management strategies appeared in the first 100 yr and were related primarily to the rate of treatment. By the second 100 yr, when all watersheds had been treated, the principal difference between logging strategies was the timing of impacts. (ii) Dispersing harvest units did not significantly reduce cumulative effects. (iii) The frequency of bed elevation changes between 1 and 4 cm is dramatically increased by logging. uncertainty in a model. These properties are essential for the characterization of meteorological inputs and can be used to account for uncertainty in hydrologic and geomorphic parameters. Paired-watershed experiments are frequently used to investigate the effects of land use on hydrologic processes. Normally the results of paired-watershed experiments are assumed to be more real than those obtained from computer simulations. That assumption should be scrutinized a little more carefully. Paired-watershed experiments record the natural interplay of all the relevant processes. They do so, however, at one location during a relatively short period of time. Therefore, statistical inferences of such studies apply only to the study watersheds and only to the conditions operating during the study periods. All else is extrapolation based on professional judgement, not statistical inference.

Although erosion-hazard ratings are often used to guide forest practices, those used in California from 1974 to 1982 have been inadequate for estimating erosion potential. To improve the erosion-hazard rating procedure, separate estimating equations were used for different situations. The ratings were partitioned according to yarding method, erosional process, and both yarding method and erosional process. Partitioning by yarding method resulted in a slight improvement in the precision of erosion estimates. The other two methods resulted in fourfold increases in prediction errors. Results indicate that a single unified erosion-hazard rating procedure is the most practical way of predicting logging-related erosion in northwestern California.

One hundred ten white-footed mice (Peromyscus leucopus) were captured on horse farms in south-central Maryland, examined for ticks, and tested for specific antibodies to Ehrlichia risticii, the causative agent of Potomac horse fever. Peromyscus leucopus were consistently infested with immature American dog ticks (Dermacentor variabilis), with monthly prevalences as high as 80%. Sera from all 97 P. leucopus tested for antibodies to E. risticii were negative. This indicates that P. leucopus is not a reservoir of E. risticii, and suggests that immature D. variabilis do not acquire E. risticii in feeding upon white-footed mice.

The genetic and antigenic relatedness of eight antigens in three strains of Rickettsia tsutsugamushi has been studied by using recombinant organisms expressing epitopes of the 150-, 110-, 72-, 58-, 56-, 49-, 47-, and 20-kilodalton (kDa) polypeptide antigens of the Karp strain. Southern blot analysis of Karp, Kato, and Gilliam strain genomic DNA by using probes specific for each antigen class indicated that while strong homology exists between each of the corresponding antigen genes in these three strains, some restriction fragment length polymorphism exists. Antibodies affinity purified against each recombinant antigen class reacted with a comparably sized polypeptide in the Karp, Kato, and Gilliam strains in Western blots (immunoblots). Against more recent human isolates of R. tsutsugamushi, the affinity-purified antibodies against the 58-kDa recombinant antigen (anti-58-kDa) reacted with all nine isolates, anti-56-kDa reacted with eight of nine isolates, anti-47-kDa reacted with eight of nine isolates, anti-72-kDa reacted with eight of nine isolates, and anti-110-kDa reacted with four of nine isolates. Additional analysis indicated that the 110-kDa antigen may contain strain-specific epitopes similar to those previously reported for the 56-kDa polypeptide. Evidently, the strain heterogeneity among scrub typhus rickettsiae is a result of multiple components that exhibit variability in a background of strong homology.

The conversion of brush areas to grassland increased soil slip erosion on mountainous watersheds in southern California during the intense winter storms of 1969. The incidence of soil slippage, site factors affecting slope stability, and amount of debris generated by slippage were investigated for sample brush and grass areas in the San Dimas Experimental Forest. Soil slippage occurred on 5.5% of the brush areas and 16.7% of the grass areas, the values for both areas being about twice those measured in 1966 for a less intense storm period. The effectiveness of linear discriminant analysis was below that of 1966. In all probability, the thresholds of several environmental factors are not linear, and the 1969 storms crossed the thresholds of several factors responsible for more widespread slippage.

Soil slippage, a form of shallow mass soil movement, was studied on the San Dimas Experimental Forest in southern California after several large storms in 1965 and 1966. The three-part study consisted of analyzing topographic data from 200 random points measured photogrammetrically; measuring soil texture, soil depth, wettability of surface soil, and hydraulic conductivity of slip surface on slipped and stable sites; and mapping and analyzing soil slips to assess the effects of watershed variables. All slips occurred on slopes greater than 80%. The ocurrence of slips was inversely related to the size and density of vegetation. In brush areas, northerly aspects were more stable than southerly ones. Conversion from brush to grass on the experimental forest may have resulted in an additional 135 m3/ha of soil slip erosion during the winter of 1965–1966.

Fifty-five horses were inoculated IV and/or SC with materials containing Ehrlichia risticii, ie, infected whole blood, buffy coat cells, or cell culture, to study clinical and hematologic features of equine monocytic ehrlichiosis (Potomac horse fever). Major clinical and hematologic features of induced E risticii infection were biphasic increase in rectal temperature with peak increases of 38.9 C and 39.3 C on postinoculation days (PID) 5 and 12, respectively; depression; anorexia; decreased WBC count (maximal decrease of 47% on PID 12); and diarrhea from PID 14 to PID 18. Increased WBC count was an inconsistent feature, with a maximal increase of 51.5% on PID 20. During times of decreased and increased WBC counts, lymphocyte/neutrophil ratios remained fairly constant. However, not all horses had all clinical and hematologic features, and these features were present in different degrees among horses. Increased rectal temperature, depression, anorexia, and decreased WBC count were more consistent features, whereas diarrhea developed in 73% of the horses. Of 55 horses, 39 (71%) had all clinical and hematologic features of the disease (classic disease), whereas 16 (29%) horses did not have greater than or equal to 1 of these features (nonclassic disease). The E risticii titer in the blood (ehrlichemia) was maximum during the peak increase in rectal temperature. In 55 horses, mortality was 9%. Significant differences (P greater than 0.5) in clinical and hematologic features were not detected between horses that survived and those that died of E risticii infection.

An indirect enzyme-linked immunosorbent assay (ELISA) was developed which was specific and sensitive in detecting antibodies to Ehrlichia risticii in Potomac horse fever (PHF). The ELISA antibody titers were correlated with the indirect fluorescent antibody (IFA) titers. E. risticii propagated in human histiocyte culture was purified on renografin gradient and the band of the organisms at a density of 1.182 g/ml was used as antigen. ELISA antibody titers were determined through computer assisted analysis, the observed antibody titers were derived by serial serum dilutions and using a resultant standard curve the predicted antibody titers were obtained from a single serum dilution. The standard curve had a correlation coefficient of 0.8975. The observed and predicted antibody titers were in good agreement, as the respective titers fell within a two-fold range. There was a good correlation between ELISA and IFA test results, but the ELISA titers were several times higher. In experimental infections of horses produced with the infected equine whole blood and the Ehrlichia infected macrophage culture, the antibodies were first detected in two weeks and one week postinoculation (PI), respectively. In both cases the titers reached a peak in about 4 weeks PI with a mean titer of 1:16558 and 1:4030, respectively. The antibody titers of the convalescent sera of field cases of PHF were comparatively lower than the experimentally infected horses.

From these studies it is concluded that: 1) Physical characteristics of wound dressings can be quantified and evaluated for their contribution to in vivo performance. 2) A total performance scoring system can be reliably used to quantitatively separate series of wound dressings by their in vivo performances. 3) The physical characteristics most determinate of good perfprmance in these 5 series of dressings were undersurface texture and water vapor transmission.

SummaryStreptomycin appears chemotherapeutically effective against pleuropneumonia infections and resultant polyarthritis in rats, and better in this respect than certain gold salts. The streptomycin which we used contained 250 units per mg, and was supplied by Dr. J. A. Leighty.

Lienhard's [1964] introduction of Boltzmann statistics as a device for hydrograph description may prove to be a valuable contribution. His derivation is impressive, but it seems to imply an unwarranted degree of objectivity. Since his successful fitting of a hydrograph depends on the proper choice of a zero time, it is no less empirical than more frankly iterative procedures. Lienhard's approach to the problem seems short sighted and his major thesis seems unwarranted by his presentation. By maintaining that the shape of the hydrograph is virtually independent of watershed properties, he negates one of the principal motivations for the development of such hydrographs, that is, interpolating to ungaged watershed relationships developed in gaged drainage basins. Although the theoretical generation of a hydrograph is in itself a fit topic for investigation, I do not feel that it is useful to pursue a line of study that is unrelated to the real world.