Statistical investigation of a sample survey for obtaining farm facts

1. A number of the problems of sampling farm facts by means of two sample surveys taken in Iowa have been studied statistically. These were essentially problems of sampling efficiency and the detection and measurement of biases and other errors in the data. 2. A sample survey of 800 farms provided estimates for the state of Iowa which were in many cases as accurate or even more accurate than corresponding information provided by the Federal Census, Iowa State Farm Census or Federal Agricultural Marketing Service. On the other hand, it was found that some items cannot be accurately estimated from a small (800 farm) sample survey, but these items are in many cases only of minor importance. 3. The sampling methods used in these experimental surveys were found to be not only relatively free of bias but also satisfactorily efficient. Certain modifications, however, have been recommended. Some principles have been suggested for modifying size of sampling unit for maximum efficiency when certain cost situations are given. Another feature of the sampling method is that it provides a basis for making unbiased estimates of total number of farms and total land in farms in any desired area and, therefore, is independent of any other source of information. 4. It has been found that wide geographical distribution of sampling units (that is, geographical stratification into small areas) Substantially reduces sampling error. Stratification by tenure group would bring only small gains if any. 5. A method has been proposed for determining the best size of sampling unit for given cost situations and for given expenditure levels. It was concluded that the quarter-section grid is an efficient sampling unit under widely varying circumstances. For investigations requiring very short interviews the half-section grid appears to have important advantages. For general inquiries (such as the census, for example), large blocks such as townships appear to be very inefficient sampling units. 6. Matching samples has proved to be an efficient method of measuring differences between years. Compared with samples taken independently each year, matched samples are from 2.5 to over 20 times as efficient, depending upon the item

Pioneer 10 and Voyager observations of the interstellar medium in scattered emission of the He584 A and H Lya 1216 A lines

The combination of Pioneer photometric and Voyager spectrometric observations of EUV interstellar-interplanetary emissions in the region beyond 5 A was applied to a determination of atomic hydrogen and helium densities. These density estimates obtained from direct measurement of scattered radiation depend on absolute calibration of the instruments in the same way as other earlier determinations based on the same method. However, the spacecraft data were combined with daily full sun averages of the H Lyman 1216 A line obtained by the Solar Mesospheric Explorer satellite to obtain a measure of atomic hydrogen density independent of instrument absolute calibration. The method depends on observations of long and short term temporal variability of the solar line over a one year period, and the fact that the ISM is optically thick. The density estimates from preliminary work on these observations are H = 0.12 cu cm and H = .016 cu cm, giving a density ratio close to the cosmic abundance value in contrast to some earlier results indicating a depletion of atomic hydrogen. Estimates were obtained of galactic background emissions in the signals of both spacecraft

A lattice of double wells for manipulating pairs of cold atoms

We describe the design and implementation of a 2D optical lattice of double wells suitable for isolating and manipulating an array of individual pairs of atoms in an optical lattice. Atoms in the square lattice can be placed in a double well with any of their four nearest neighbors. The properties of the double well (the barrier height and relative energy offset of the paired sites) can be dynamically controlled. The topology of the lattice is phase stable against phase noise imparted by vibrational noise on mirrors. We demonstrate the dynamic control of the lattice by showing the coherent splitting of atoms from single wells into double wells and observing the resulting double-slit atom diffraction pattern. This lattice can be used to test controlled neutral atom motion among lattice sites and should allow for testing controlled two-qubit gates.Comment: 9 pages, 11 figures Accepted for publication in Physical Review

Detrimental adsorbate fields in experiments with cold Rydberg gases near surfaces

We observe the shift of Rydberg levels of rubidium close to a copper surface when atomic clouds are repeatedly deposited on it. We measure transition frequencies of rubidium to S and D Rydberg states with principal quantum numbers n between 31 and 48 using the technique of electromagnetically induced transparency. The spectroscopic measurement shows a strong increase of electric fields towards the surface that evolves with the deposition of atoms. Starting with a clean surface, we measure the evolution of electrostatic fields in the range between 30 and 300 \mum from the surface. We find that after the deposition of a few hundred atomic clouds, each containing ~10^6 atoms, the field of adsorbates reaches 1 V/cm for a distance of 30 \mum from the surface. This evolution of the electrostatic field sets serious limitations on cavity QED experiments proposed for Rydberg atoms on atom chips.Comment: 4 pages, 3 figures Submitted to Phys. Rev.

Statistical investigations of farm sample surveys taken in Iowa, Florida and California

The object of this bulletin is to present results of statistical analyses of data from recent sample surveys of agricultural areas and to offer some comments on the sampling procedures followed. The surveys described herein were made in widely differing farming areas: In all of the 99 counties of Iowa, in 26 of the 67 counties in Florida, and in 9 of the 58 counties of California. Except for Iowa (3) these surveys were pioneering a sampling method in their respective areas. In order to observe the way in which this method behaved in different parts of the country we have brought the findings together under one cover

Some investigations on the suitability of the township as a unit for sampling Iowa agriculture

The purpose of this study was to determine a sampling procedure by which agricultural information may be efficiently obtained for areas smaller than the state, particularly the county. This study, therefore, is one of a series (2) (4) directed toward the problems of methodology of an agricultural sample-census. The objectives (8) of such a sample-census are: To obtain useful information (a) more frequently (annually instead of quinquennially, as at present), (b) of greater extent (include items not covered by the regular census) and (c) at greater economy. Consequently the sample-census is proposed at least in part to supplement the regular census in providing the information needed in the analysis and understanding of special agricultural problems arising in the field of policy and programs, such as farm tenancy, soil conservation, etc. This study, however, is limited to an investigation of merely a few of the many problems of sample-census procedure. Here we are interested primarily in the following questions: 1. Is it possible to find a township or group of townships within a county which will satisfactorily represent that county for a period of years? 2. For a given degree of accuracy, how large must a sample he for (a) a county, (b) a crop-reporting district (a group of about 10 counties)? 3. Are there any satisfactory criteria by which a county may be stratified and thereby increase sampling efficiency? This study provides, we believe, some aid in answering these and allied questions

Bloch Structures in a Rotating Bose-Einstein Condensate

A rotating Bose-Einstein condensate is shown to exhibit a Bloch band structure without the need of periodic potential. Vortices enter the condensate by a mechanism similar to the Bragg reflection, if the frequency of a rotating drive or the strength of interaction is adiabatically changed. A localized state analogous to a gap soliton in a periodic system is predicted near the edge of the Brillouin zone.Comment: 4 pages, 3 figure

Synthesis and Structural Investigation of Protonated Haloacetyl Fluorides

Herein, we report the O-monoprotonated species of chloroacetyl fluoride and fluoroacetyl fluoride in the binary superacidic systems HF/MF5 and DF/MF5 (M=As, Sb) as hexafluoridoarsenates and hexafluoridostibates. The colorless salts were characterized by low temperature vibrational spectroscopy, low temperature NMR spectroscopy and single-crystal X-ray diffraction. [CCIH2C(OH)F][SbF6] crystallizes in the monoclinic space group P2(1)/c with four formula units per unit cell and [CIH2FC-(OD)F][SbF6] in the triclinic space group P (1) over bar with two formula units per cell. The experimental data are discussed together with quantum chemical calculations at the omega B97XD/aug-cc-pVTZ-level of theory. Protonation leads to significant shortening of the C F bond due to back-donation of fluorine lone-pair electrons

Observations of the magnetic field and plasma flow in Jupiter's magnetosheath

Large scale (many minutes to 10 hours) magnetic field structures consisting predominantly of nearly north-south field direction were discovered in Jupiter's magnetosheath from the data of Voyagers 1 and 2 and Pioneer 10 during their outbound encounter trajectories. The Voyager 2 data, and that of Voyager 1 to a lesser extent, show evidence of a quasi-period of 10 hours (and occasionally 5 hours) for these structures. The north-south components of the field and plasma velocity were strongly correlated in the outbound magnetosheath as observed by Voyagers 1 and 2, and the components orthogonal to the north-south direction showed weak correlations. For both Voyager encounters the sense (positive and negative) of the north-south correlations were directly related to the direction of the ecliptic plane component of the interplanetary magnetic field using the field and plasma measurements of the non-encountering spacecraft