A Simplified Cellular Automaton Model for City Traffic

We systematically investigate the effect of blockage sites in a cellular automaton model for traffic flow. Different scheduling schemes for the blockage sites are considered. None of them returns a linear relationship between the fraction of ``green'' time and the throughput. We use this information for a fast implementation of traffic in Dallas.Comment: 12 pages, 18 figures. submitted to Phys Rev

Conidial Production in the Genus Cercospora

One of the limiting factors in the study of the biology of several species of the genus Cercospora has been the failure of investigators to obtain conidia abundantly and at will in pure culture

Nachhaltige Verbesserung der Verfügbarkeit ökologisch vermehrten Gemüsesaatguts für den Erwerbsanbau durch on-farm Erhaltung, Züchtung und Vermehrung

Die Verfügbarkeit von ökologisch vermehrtem Saatgut bzw. die Sortenauswahl wird insbesondere bei Gemüse als unzureichend eingestuft. Die verwendeten Sorten sind bei vielen Gemüsekulturen zum überwiegenden Teil Hybriden, die für eine /On-farm/-Erhaltung ungeeignet sind oder im Falle von aus Zellfusion (Protoplasten- oder Cytoplastenfusion) stammenden CMS-Hybriden nicht mehr fertil und auf Betrieben der Ökolandbauverbände per Richtlinie verboten sind. Diese beiden Aspekte der Saatgutfrage waren maßgebend für den Start dieses Projektes. Mit dem Ziel, die Eignung der Sorten für den ökologischen Gemüsebau zu prüfen, wurden 164 Saatgutmuster noch verfügbarer Populationssorten der Kulturen Kohlrabi (15), Möhren (86) und Porree (63) am europäischen Saatgutmarkt erworben und als Ausgangsmaterial für die Sichtungen verwendet. Dafür wurden an elf Standorten in Deutschland, den Niederlanden und der Schweiz über zwei Jahre 143 Sorten gesichtet und von mehr als der Hälfte der Sorten erhaltungszüchterischer Samenbau durchgeführt. Sorten, die auf Basis der Sichtungen als für den ökologischen Erwerbsgemüsebau unmittelbar geeignet eingestuft worden sind, werden in weiterführenden (teilweise externen) Versuchsanbau gestellt. Außerdem werden dafür ökologische Erhaltungszuchten bzw. Saatgutvermehrungen aufgebaut, die teilweise bereits in der Projektlaufzeit initiiert wurden. Sorten, die einer züchterischen Weiterentwicklung bedürfen, stehen als Ausgangsmaterial für ökologische Zuchtprogramme zur Verfügung. Das Saatgut wird über eine vereinseigene Genbank zentral verwaltet. Die Ergebnisse der Sichtungen, sowie Sortenbeschreibungen sind in einer Online-Datenbank veröffentlicht: www.kultursaat.org/index.ph

Tomato Leaf Spot Control

The most important plant disease affecting tomatoes during the past 10 years in South Dakota has been a fungus disease known as Septoria leaf spot (Septoria lycopersici). Other diseases have been of minor importance, namely late blight, Alternaria leaf spot, wilt and virus troubles. Septoria leaf spot frequently develops rapidly and may, under favorable conditions, completely defoliate the crop within a few weeks. When defoliation by the disease occurs, the yield may be markedly reduced. Fruit produced on such plants becomes flabby and the flavor is of low quality. The tomato is one of our most important vegetable crops. It is grown by virtually every home gardener and is high in certain vitamins which are important in the family diet, though it is not grown extensively on a commercial scale in the state at the present time. Septoria leaf spot may be recognized by the characteristic spots (see cover) on the leaves and stems which are approximately one-eighth inch in diameter. The margins of the spots usually become dark reddish- brown in color while the centers are light grey with a few scattered tiny black specks. When the spots become very numerous the affected leaves turn from light green to brown, die and drop from the plants. When the leaves are killed by the disease the fruits ripen prematurely and have an insipid flavor. These symptoms should distinguish Septoria leaf spot from other fungus diseases affecting the foliage. Early blight (Alternaria solani) forms larger irregular spots onefourth to one-half inch in diameter with numerous inconspicuous concentric rings within the diseased spot. Late blight (Phytophthora infestans) forms larger patches on the leaves which may, under certain weather conditions, involve entire leaves. The lesions appear water-soaked at first, but later become light brown to dark brown and in moist weather show a white mildew-like growth on the lower side of the leaves. This disease also causes a characteristic brown rot of the fruit which may result in heavy losses in yield of marketable fruit. Tomato plants can be protected from these fungus diseases by repeated applications with an effective fungicide. The first application should be made when the leaf spots first appear, and then repeated at 10-day intervals. It has been shown experimentally that sprays provide better coverage and protection than dusts. The lower as well as the upper surfaces of the leaves should be covered. In order to determine the most effective fungicide for the control of tomato foliage diseases in South Dakota a series of field experiments was started in 1944 at the State College Experiment Station

Fungicides for Potato Blight Control

South Dakota has an important potato- growing area in Clark, Codington, Hamlin and Deuel counties. Production of certified seed has become one of the important phases of the potato industry in South Dakota. In addition to the main commercial seed and table stock production areas indicated above, smaller producing areas are located in various sections of the state, not to mention the familiar potato patch in most home gardens. Likewise, with the coming of irrigation in the James River Valley of South Dakota, potato production will probably increase further. Losses in yield and quality of potatoes are severe in seasons favorable to the development of foliage diseases. While these diseases do not occur in serious amounts every season in South Dakota, the profits may be wiped out in those years when they are prevalent. When these diseases strike in epidemic proportions, one of the important effects which they have on the crop is the prevention of normal sizing of the tubers, thereby resulting in a reduction of U. S. No. 1 potatoes. For this reason, it is important to know what control measures are effective and can be easily and quickly applied when these diseases strike the crop. An effective fungicide, properly applied, can control these foliage diseases, and by removing another crop hazard can thereby add to the stability of commercial and certified seed potato production in South Dakota. Chemical fungicides, applied as sprays or dusts, differ in their effectiveness in controlling crop diseases. A particular fungicide might be highly effective in combating one type of disease, but may not be very effective against another. Consequently, it becomes necessary to test many chemicals over a period of several years to determine their effectiveness as well as the dosage rate and the proper time of the season to apply them. The most prevalent fungus diseases affecting potato foliage in the state are early blight, caused by Alternaria solcmi, and late blight, caused by Phytophthora infestans. Early blight is present to some extent every season in South Dakota, and causes losses through reduced grade and yield. The disease first appears as small oval or angular brown spots on the leaves with characteristic target-like markings. As the spots increase in size and number the affected leaves die. As a result of this defoliation the yield, especially of U. S. No. 1 grade potatoes, is reduced. During those seasons when conditions are favorable for the development of late blight, losses through reduced yields and tuber rot become costly to potato growers. Late blight is favored by cool temperatures and relatively good moisture conditions. This disease first appears on the leaves as pale green, water-soaked, irregular-shaped spots which may enlarge rapidly, turn brown or black, and show a white mildew-like appearance on the lower surface of diseased leaves. The stems can become infected and the entire plant may be killed in a few days. Under conditions favorable for the disease (moderate temperatures, with high humidity, heavy clews or frequent rains), it can spread rapidly throughout a field. Spores from diseased foliage washed down to the tubers by rain or brought in contact with them during digging operations can expose tubers to infection with late blight. Late blight-infected tubers develop what is known as late blight tuber rot, either in the field or in storage. To protect potato plants from these fungus diseases, it is necessary to keep the foliage coated with an effective fungicide. It has been shown experimentally that fungicides applied as sprays provide better coverage and disease control than those applied as dusts. A series of field experiments were initiated in 1945 at the Experiment Station at Brookings with the object of developing a potato spray program adapted to South Dakota conditions. In 1946, these tests formed a part of a regional potato fungicide trial in which six states in the upper Mississippi Valley participated. From 1947 to 1949 the tests were included in the national cooperative fungicide experiments sponsored by a Special Committee on the Coordination of Field Tests with New Fungicidal Sprays and Dusts, appointed by the American Phytopathological Society

Do wildflower strips enhance pest control in organic cabbage?

Within this project we assess whether wildflower strips and companion plants increase the control of cabbage pests Plutella xylostella L. (Lepidoptera: Plutellidae), Mamestra brassicae L. (Lepidoptera: Noctuidae) and Pieris rapae L. (Lepidoptera: Pieridae) by (1) naturally occurring parasitoids and predators and (2) mass‐releasedn Trichogramma brassciae (Bezdenko) (Hymenoptera: Trichogrammatidae) parasitoids. Two organic cabbage fields were used for this study: adjacent to each field a wildflower strip was sown and companion plants (Centaurea cyanus L. (Asteraceae)) intermixed within the crop. Within each field ~15,000 M. brassicae eggs were placed out to determine the parasitism rates by mass‐released T. brassicae and to assess the levels of egg predation. Over 1,000 lepidopteran larvae were collected and screened for hymenopteran and tachinid parasitoid DNA using a multiplex PCR assay. Invertebrate generalist predators (n=1,063) were collected for DNA‐based gut content analysis. The wildflower strip had a significant positive effect on M. brassicae egg parasitism rates as rates increased 5‐fold in the vicinity to the strip. Moreover, companion plants enhanced invertebrate predation on M. brassicae eggs. Both, the release of T. brassicae and the use of companion plants, however, did not significantly increase egg parasitism rates. The infestation of plants by caterpillars increased with distance to the wildflower strip and there was a trend of decreasing larval parasitism rates with distance to the strip. Currently the invertebrate predators are being molecularly analysed to assess predation on unparasitized and parasitized lepidopteran pests

Observations on mold development and on deterioration in stored yellow dent shelled corn

Examinations during 3 consecutive years were made in Iowa for mold development in yellow dent shelled corn stored in steel bins of 1,000-2,740 bushel capacities. The first was made during August and September 1941, the second in March 1942 and the third in April 1943. Different bins were examined in each of the three inspections. Bins reportedly containing some corn of 14 percent or more moisture were examined and probed in the first examination, those with corn of 13.5 percent or more moisture in the second examination; no selection of bins for moisture content was made in the third examination. All of the bins examined had been filled during the fall previous to sampling

Suppression of spin-state transition in epitaxially strained LaCoO_{3}

Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.Comment: 5 pages, 5 figures, submitted to Physical Review

The Effect of absorbing sites on the one-dimensional cellular automaton traffic flow with open boundaries

The effect of the absorbing sites with an absorbing rate $\beta_{0}$, in both one absorbing site (one way out) and two absorbing sites (two ways out) in a road, on the traffic flow phase transition is investigated using numerical simulations in the one-dimensional cellular automaton traffic flow model with open boundaries using parallel dynamics.In the case of one way out, there exist a critical position of the way out $i_{c1}$ below which the current is constant for $\beta_{0}$$<$$\beta_{0c2}$ and decreases when increasing $\beta_{0}$ for $\beta_{0}$$>$$\beta_{0c2}$. When the way out is located at a position greater than $i_{c2}$, the current increases with $\beta_{0}$ for $\beta_{0}$$<$$\beta_{0c1}$ and becomes constant for any value of $\beta_{0}$ greater than $\beta_{0c1}$. While, when the way out is located at any position between $i_{c1}$ and $i_{c2}$ ($i_{c1}$$<$$i_{c2}$), the current increases, for $\beta_{0}$$<$$\beta_{0c1}$, with $\beta_{0}$ and becomes constant for $\beta_{0c1}$$<$$\beta_{0}$$<$$\beta_{0c2}$ and decreases with $\beta_{0}$ for $\beta_{0}$$>$$\beta_{0c2}$. In the later case the density undergoes two successive first order transitions; from high density to maximal current phase at $\beta_{0}$$=$$\beta_{0c1}$ and from intermediate density to the low one at $\beta_{0}$$=$$\beta_{0c2}$. In the case of two ways out located respectively at the positions $i_{1}$ and $i_{2}$, the two successive transitions occur only when the distance $i_{2}$-$i_{1}$ separating the two ways is smaller than a critical distance $d_{c}$. Phase diagrams in the ($\alpha,\beta_{0}$), ($\beta,\beta_{0}$) and ($i_{1},\beta_{0}$) planes are established. It is found that the transitions between Free traffic, Congested traffic and maximal current phase are first order