Potato growing in Iowa as affected by temperature

The white potato is distinctively a cool-season crop. On the average the best yields are secured by planting early in order to get the crop as far along as possible in advance of the high summer temperatures. The heaviest yields, on the average, were secured from the plantings made shortly after the seasonal rise in temperature crosses the 40° line. For central Iowa, this period is usually reached during the first half of April. In a date-of-planting-in-relation-to-yield experiment with late potatoes, covering six years, the results were as follows: The average of the April plantings was 124.4 bushels per acre and for the June plantings, 76.2 bushels. The planting dates covered by the last week of April and the first two weeks in May averaged about the same. The plantings made after the middle of May gave a successive decline in yield. Between the first and last planting there was a spread of 65.8 bushels per acre. The minimum vegetative temperature for corn is fully ten degrees above that for potatoes. The general practice of planting late potatoes after corn planting is contrary to the temperature requirements of the two crops, and is regarded as one of the important reasons for the decline in potato yields in Iowa. In general, the early market is the most profitable. Early planting and early marketing go hand in hand. The danger from frost injury at harvest time may be largely eliminated by early planting

Extragalactic Radio Sources and the WMAP Cold Spot

We detect a dip of 20-45% in the surface brightness and number counts of NVSS sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of approximately 1-10 degrees. Together with independent all-sky wavelet analyses, our results suggest that the dip in extragalactic brightness and number counts and the WMAP cold spot are physically related, i.e., that the coincidence is neither a statistical anomaly nor a WMAP foreground correction problem. If the cold spot does originate from structures at modest redshifts, as we suggest, then there is no remaining need for non-Gaussian processes at the last scattering surface of the CMB to explain the cold spot. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, can now be seen to operate on a single region. To create the magnitude and angular size of the WMAP cold spot requires a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This is far outside the current expectations of the concordance cosmology, and adds to the anomalies seen in the CMB.Comment: revised version, ApJ, in pres

The effective potential, critical point scaling and the renormalization group

The desirability of evaluating the effective potential in field theories near a phase transition has been recognized in a number of different areas. We show that recent Monte Carlo simulations for the probability distribution for the order parameter in an equilibrium Ising system, when combined with low-order renormalization group results for an ordinary $\phi^4$ system, can be used to extract the effective potential. All scaling features are included in the process.Comment: REVTEX file, 22 pages, three figures, submitted to Phys. Rev.

Solving the Cooling Flow Problem of Galaxy Clusters by Dark Matter Neutralino Annihilation

Recent X-ray observations revealed that strong cooling flow of intracluster gas is not present in galaxy clusters, even though predicted theoretically if there is no additional heating source. I show that relativistic particles produced by dark matter neutralino annihilation in cluster cores provide a sufficient heating source to suppress the cooling flow, under reasonable astrophysical circumstances including adiabatic growth of central density profile, with appropriate particle physics parameters for dark matter neutralinos. In contrast to other astrophysical heat sources such as AGNs, this process is a steady and stable feedback over cosmological time scales after turned on.Comment: 4 pages, no figure. Accepted to Phys. Rev. Lett. A few minor revisions and references adde

The shape of invasion perclation clusters in random and correlated media

The shape of two-dimensional invasion percolation clusters are studied numerically for both non-trapping (NTIP) and trapping (TIP) invasion percolation processes. Two different anisotropy quantifiers, the anisotropy parameter and the asphericity are used for probing the degree of anisotropy of clusters. We observe that in spite of the difference in scaling properties of NTIP and TIP, there is no difference in the values of anisotropy quantifiers of these processes. Furthermore, we find that in completely random media, the invasion percolation clusters are on average slightly less isotropic than standard percolation clusters. Introducing isotropic long-range correlations into the media reduces the isotropy of the invasion percolation clusters. The effect is more pronounced for the case of persisting long-range correlations. The implication of boundary conditions on the shape of clusters is another subject of interest. Compared to the case of free boundary conditions, IP clusters of conventional rectangular geometry turn out to be more isotropic. Moreover, we see that in conventional rectangular geometry the NTIP clusters are more isotropic than TIP clusters

Chandra Detection of the Forward and Reverse Shocks in Cassiopeia-A

We report the localization of the forward and reversed shock fronts in the young supernova remnant Cas-A using X-ray data obtained with the Chandra Observatory. High resolution X-ray maps resolve a previously unseen X-ray feature encompassing the extremity of the remnant. This feature consists of thin, tangential wisps of emission bordering the outer edge of the thermal X-ray and radio remnant, forming a circular rim, approx. 2.7 in radius. Radio images show a sharp rise in brightness at this X-ray rim, along with a large jump in the synchrotron polarization angle. These characteristics suggest that these wisps are the previously unresolved signature of the forward, or outer, shock. Similarly, we identify the sharp rise in emissivity of the bright shell for both the radio and X-ray line emission associated with the reverse shock. The derived ratio of the averaged forward and reverse shock radii of approx. 3:2 constrains the remnant to have swept up roughly the same amount of mass as was ejected; this suggests that Cas-A is just entering the Sedov phase. Comparison of the X-ray spectra from the two shock regions shows that the equivalent widths of prominent emission lines are significantly lower exterior to the bright shell, as expected if they are respectively identified with the shocked circumstellar material and shocked ejecta. Furthermore, the spectrum of the outer rim itself is dominated by power-law emission, likely the counterpart of the non-thermal component previously seen at energies above 10 keV.Comment: 7 pages with 5 figures, LaTex, emulateapj.sty. To appear in the Astrophysical Journal Letter

Organized condensation of worm-like chains

We present results relevant to the equilibrium organization of DNA strands of arbitrary length interacting with a spherical organizing center, suggestive of DNA-histone complexation in nucleosomes. We obtain a rich phase diagram in which a wrapping state is transformed into a complex multi-leafed, rosette structure as the adhesion energy is reduced. The statistical mechanics of the "melting" of a rosette can be mapped into an exactly soluble one-dimensional many-body problem.Comment: 15 pages, 2 figures in a pdf fil

Cassiopeia A: dust factory revealed via submillimetre polarimetry

If Type-II supernovae - the evolutionary end points of short-lived, massive stars - produce a significant quantity of dust (>0.1 M_sun) then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe. Submillimetre observations of the Galactic supernova remnant, Cas A, provided the first observational evidence for the formation of significant quantities of dust in Type-II supernovae. In this paper we present new data which show that the submm emission from Cas A is polarised at a level significantly higher than that of its synchrotron emission. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarised submm emission is associated with the remnant. No known mechanism would vary the synchrotron polarisation in this way and so we attribute the excess polarised submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. This is supported by the presence of both polarised and unpolarised dust emission in the north of the remnant, where there is no contamination from foreground molecular clouds. The inferred dust polarisation fraction is unprecedented (f_pol ~ 30%) which, coupled with the brief timescale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where f_pol=2-7%), or that a highly efficient grain alignment process must operate in the environment of a supernova remnant.Comment: In press at MNRAS, 10 pages, print in colou

The Mechanical Penetration of the Sweet Corn Pericarp

Hawkins and Harvey, Rosenbaum and Sando, and Hawkins and Sando have used a modified Joly balance fitted with a puncturing needle to determine the force necessary to puncture the cells of the potato tuber, tomato, and certain smaller fruits. For the penetration of these tissues a relatively small force is necessary