The Farm Tractor in Iowa

Tractors have been sold In large numbers to Iowa farmers In the past two years. From the best Information available It Is estimated that there are something like 12,000 tractors In the state. This means that about one farm In 16 has a tractor

Renormalization constants and beta functions for the gauge couplings of the Standard Model to three-loop order

We compute the beta functions for the three gauge couplings of the Standard Model in the minimal subtraction scheme to three loops. We take into account contributions from all sectors of the Standard Model. The calculation is performed using both Lorenz gauge in the unbroken phase of the Standard Model and background field gauge in the spontaneously broken phase. Furthermore, we describe in detail the treatment of $\gamma_5$ and present the automated setup which we use for the calculation of the Feynman diagrams. It starts with the generation of the Feynman rules and leads to the bare result for the Green's function of a given process.Comment: 44 pages, 9 figures; v2: sign in eq.(29) corrected; final result unchange

A stochastic model for early placental development

In the human, placental structure is closely related to placental function and consequent pregnancy outcome. Studies have noted abnormal placental shape in small-for-gestational age infants which extends to increased lifetime risk of cardiovascular disease. The origins and determinants of placental shape are incompletely under-stood and are difficult to study in vivo. In this paper we model the early development of the placenta in the human, based on the hypothesis that this is driven by dynamics dominated by a chemo-attractant effect emanating from proximal spiral arteries in the decidua. We derive and explore a two-dimensional stochastic model for these events, and investigate the effects of loss of spiral arteries in regions near to the cord insertion on the shape of the placenta. This model demonstrates that placental shape is highly variable and disruption of spiral arteries can exert profound effects on placental shape, particularly if this disruption is close to the cord insertion. Thus, placental shape reflects the underlying maternal vascular bed. Abnormal placental shape may reflect an abnormal uterine environment, which predisposes to pregnancy complications

A Pinned Polymer Model of Posture Control

A phenomenological model of human posture control is posited. The dynamics are modelled as an elastically pinned polymer under the influence of noise. The model accurately reproduces the two-point correlation functions of experimental posture data and makes predictions for the response function of the postural control system. The physiological and clinical significance of the model is discussed.Comment: uuencoded post script file, 17 pages with 3 figure

Next-to-leading-order corrections to exclusive processes in kTk_T factorization

We calculate next-to-leading-order (NLO) corrections to exclusive processes in $k_T$ factorization theorem, taking $\pi\gamma^*\to\gamma$ as an example. Partons off-shell by $k_T^2$ are considered in both the quark diagrams from full QCD and the effective diagrams for the pion wave function. The gauge dependences in the above two sets of diagrams cancel, when deriving the $k_T$-dependent hard kernel as their difference. The gauge invariance of the hard kernel is then proven to all orders by induction. The light-cone singularities in the $k_T$-dependent pion wave function are regularized by rotating the Wilson lines away from the light cone. This regularization introduces a factorization-scheme dependence into the hard kernel, which can be minimized in the standard way. Both the large double logarithms $\ln^2k_T$ and $\ln^2 x$, $x$ being a parton momentum fraction, arise from the loop correction to the virtual photon vertex, the former being absorbed into the pion wave function and organized by the $k_T$ resummation, and the latter absorbed into a jet function and organized by the threshold resummation. The NLO corrections are found to be only few-percent for $\pi\gamma^*\to\gamma$, if setting the factorization scale to the momentum transfer from the virtual photon.Comment: 13 pages; version to appear in Physical Review

Effect of time, depth and method of plowing upon yield and eradication of biennial sweet clovers

From the standpoint of amount of dry matter and nitrogen added to the soil and the eradication of the plants, sweet clover may best be plowed for corn about April 25 to May 5. The five dates of harvest used rank as follows in yield of dry matter for tops and roots: May 3-18, Nov. 1-13, Oct. 1, April 9-13 and Sept. 1. Nitrogen yields rank in much the same order. Of the total for tops and roots, the tops contained 68 percent of the dry matter and 73 percent of the nitrogen in September, 51 and 48 percent, respectively, in October, 29 and 18 in November, 24 and 28 in April and 69 and 74 in May. In September the tops contained 3.5 percent nitrogen and the roots 2.8, October 3.0 and 3.4, respectively, November 2.1 and · 3.9, April 5.4 and 4.5 and May 3.4 and 2.6. In April the roots contained 61 percent as much dry matter and 69 percent as much nitrogen as in November. In April, however, tops and roots together contained 80 percent as much dry matter and 96 percent as much nitrogen as the roots alone in November. White sweet clover was superior to yellow in yield of dry matter in the tops, while yellow was superior to white for roots. For tops and roots there was little difference. Yellow survived somewhat more than white, but the difference was small. Plowing Sept. 1 killed nearly all of the sweet clover but with a sacrifice of approximately one-half of the dry matter and nitrogen. Plowing in October and November caused costly eradication problems since approximately 20 plants per square yard survived. The Pulverator plow was less effective than the ordinary plow in exterminating the clover for September, October, November and April plowings. A depth of plowing recognized as providing good tillage practice is to be preferred. Draft requirements were in direct proportion to the depth of plowing, and the ordinary plow required practically the same amount of draft as the Pulverator. Draft required increased progressively for September, October and November plowings, dropped sharply for April and increased for May over April. Pasturing yellow sweet clover from Aug. 15 on reduced the survival nearly 50 percent. Plants buried by hand survived directly in proportion to length of roots for 1, 3, 5 and 7-inch lengths, and inversely in proportion to depths of burying for 3, 5 and 7-inches. Fewer of the small roots survived than of the large ones. Plants transplanted in normal position had an average of eight buds per plant. On the plants that survived 51 percent of the buds produced shoots. Under field conditions there were approximately two shoots per plant. Large roots had more buds than small ones, but practically the same percentage of buds grew from large roots as from small ones. Following dormancy buds did not grow at temperatures of 28 and 30° F., increased an average of 0.5 cm. in length in 32 days at 36°, 1 cm. at 40° and 4 cm. at 50°

N∗→Nη′N^*\to N \eta^\prime decays from photoproduction of η′\eta^\prime-mesons off protons

A study of the partial-wave content of the $\gamma p\to \eta^\prime p$ reaction in the fourth resonance region is presented, which has been prompted by new measurements of polarization observables for that process. Using the Bonn-Gatchina partial-wave formalism, the incorporation of new data indicates that the $N(1895)1/2^-$, $N(1900)3/2^+$, $N(2100)1/2^+$, and $N(2120)3/2^-$ are the most significant contributors to the photoproduction process. New results for the branching ratios of the decays of these more prominent resonances to $N\eta^\prime$ final states are provided; such branches have not been indicated in the most recent edition of the Review of Particle Properties. Based on the analysis performed here, predictions for the helicity asymmetry $E$ for the $\gamma p\to \eta^\prime p$ reaction are presented.Comment: 7 pages, 5 figures, 3 table

Testing draft horses

“When animals are viewed from the standpoint of machines they are wonderful mechanisms. Not only are they self-feeding, self-controlling, self-maintaining and self-reproducing, but they are far more economical in the energy they are able to develop from a given weight of fuel material, than any other existing form of motor. While they are like the steam engine in requiring carbonaceous fuel, oxygen and water for use in developing energy; these are made to combine in the animal body at a much lower temperature than is possible in the steam engine, and a much smaller proportion of the fuel value is lost in the form of heat, when work is being done.