Spatial correlators in strongly coupled plasmas

We numerically calculate the spatial correlators of the scalar and pseudoscalar operators $F^2$ and $F\tilde F$, in SU(3) Yang-Mills theory at zero and finite-temperature on the lattice. We compare the results over the distances $\frac{1}{2T}<r<\frac{3}{2T}$ to the free-field prediction, to the operator-product expansion as well as to the strongly coupled large-$N_c$ \sN=4 super-Yang-Mills theory, where results are obtained by AdS/CFT methods. For $T_c<T<1.15T_c$, both channels exhibit stronger spatial correlations than in the vacuum, and we give an explanation for this, using sum-rules and the operator-product expansion. The AdS/CFT calculation provides a semi-quantitatively successful description of the vacuum-subtracted $F^2$ correlator, renormalized in the 3-loop $\overline{\rm MS}$ scheme, in the interval of temperatures $1.2<T/T_c<1.9$, while the free-field prediction has the wrong sign. The $F\tilde F$ and $F^2$ correlators are predicted to have the same functional form both at weak coupling and in the strongly coupled SYM theory. The Yang-Mills plasma does not meet that expectation below $2T_c$. Instead we find that strong fluctuations of $F\tilde F$ are present at least up to that temperature. We discuss the impact of our results on our understanding of the quark-gluon plasma.Comment: 32 pages, 9 figures, 4 tables; added some references, more detailed captions, conclusions unchange

Thermal compression of atomic hydrogen on helium surface

We describe experiments with spin-polarized atomic hydrogen gas adsorbed on liquid $^{4}$He surface. The surface gas density is increased locally by thermal compression up to $5.5\times10^{12}$ cm$^{-2}$ at 110 mK. This corresponds to the onset of quantum degeneracy with the thermal de-Broglie wavelength being 1.5 times larger than the mean interatomic spacing. The atoms were detected directly with a 129 GHz electron-spin resonance spectrometer probing both the surface and the bulk gas. This, and the simultaneous measurement of the recombination power, allowed us to make accurate studies of the adsorption isotherm and the heat removal from the adsorbed hydrogen gas. From the data, we estimate the thermal contact between 2D hydrogen gas and phonons of the helium film. We analyze the limitations of the thermal compression method and the possibility to reach the superfluid transition in 2D hydrogen gas.Comment: 20 pages, 11 figure

The electroclinic effect and modulated phases in smectic liquid crystals

We explore the possibility that the large electroclinic effect observed in ferroelectric liquid crystals arises from the presence of an ordered array of disclination lines and walls. If the spacing of these defects is in the subvisible range, this modulated phase would be similar macroscopically to a smectic A phase. The application of an electric field distorts the array, producing a large polarization, and hence a large electroclinic effect. We show that with suitable elastic parameters and sufficiently large chirality, the modulated phase is favored over the smectic A and helically twisted smectic C* phases. We propose various experimental tests of this scenario.Comment: 9 pages, 7 figures; new version includes dipolar interactions and bend-twist couplin

Understanding salt and sodium in soils, irrigation water and shallow groundwaters: A companion to the software program SWAGMAN-Whatif

Understanding Salt and Sodium in Soils, Irrigation Water and Shallow Groundwaters is a companion booklet to SWAGMANe-Whatif, a computer model that lets you see how salts, soils, water and water tables interact. SWAGMANkWhatif also lets you assess the effects of management practices that you might undertake in a particular area. This booklet gives background information to help you understand salts, sodium and their interactions with water and soils. It explains where sodium and salts come from, how to identify salt-affected soils, and gives instructions on taking soil and water samples for analysis. It also gives suggestions on how to reduce the harmful effects of salts and sodium, and tells you where to get advice in making reclamation and management decisions for each situation. Managing salt and sodium affected soils, together with waters used for irrigation, is complex. It is not possible to cover all technical aspects or possible treatment approaches in this booklet. Instead, we have given a simple overview of the major principles involved in diagnosing and managing salt and sodium affected soils and irrigation waters. It is difficult to summarise salt and sodium effects on soils and plants without using some technical terms, so a comprehensive glossary has been included

SWAGMAN-Whatif, an interactive computer program to teach salinity relationships in irrigated agriculture

Managing salt-affected irrigated lands and marginally salinine irrigation water requires understanding the interactions among soil salinity, crop salt tolerances, soil physical properties, irrigation water quality, irrigation management, water table depth and quality, climate, and crop yield. An interactive computer program was developed to simulate interactions among the above factors. It shows how changing one factor impacts the others for a growing season. The user selects a climate, crop, and soil characteristics from menu lists, then sets the water table depth and quality, irrigation water quality, and develops an irrigation schedule. On execution, surface runoff, water table rise or fall, and the relative yield reductions due to overirrigation, underirrigation, and salinity are shown numerically for 1 yr. Soil water content, soil salinity, water table depth changes, and rain and irrigation events are also shown graphically. An IBM-compatible computer with a math coprocessor executes the program in 6 to 10 s. This is an educational tool designed to teach the concepts of salinity and irrigation management and is not an irrigation scheduling program nor a management tool. Two versions have been developed, one using metric units, southern hemisphere growing seasons, and Australian terminology; and a second using northern hemisphere growing seasons and U.S. units and terminology. The U.S. version also allows use of metric units. The program is supplied in executable code with a user guide, a soil salinity manual, and a salinity units conversion slide rule

Predicting salinization in a heavy clay soil subjected to a saline shallow water table

Salt increase in a heavy clay soil due to capillary rise was simulated by an analytical model and a numerical model. Predicted values were compared with experimental data. The analytical model was inadequate in predicting salinisation in a dynamic crop/soil system. When root growth was accounted for, the numerical model satisfactorily predicted salt increase in the soil profile

Models for estimating capillary rise in a heavy clay soil with a saline shallow water table

Shallow saline water tables underlie large areas of the clay soils in the Murray basin of Australia. Accurate estimation of capillary rise is important in formulating management strategies to avoid degradation of such soils. Measured capillary rise from a saline water table was compared with capillary rise estimated by three mathematical models of varying complexity and input requirement. A quasi steady state analytical model (QSSAM), a transient state analytical model (TSAM) and a numerical model (NM) were used. An undisturbed heavy clay soil core of 0.75 m diameter and 1.4 m deep was subjected to a static saline water table at 1.2 m from the surface. A wheat crop was grown on the core and the weekly capillary rise from the water table was measured. The electrical conductivity of a 1 : 2 soil : water extract was determined at 0.15 m depth intervals before and 21 weeks after the introduction of the saline water table. The QSSAM did not satisfactorily estimate the initial wetting of the subsoil and the estimated capillary rise was considerably lower than the measured values. Capillary rise estimated by the TSAM was reasonably close to the measured values, but the weekly rates fluctuated considerably. The NM estimated capillary rise quite satisfactorily throughout the experiment. Except near the soil surface, the electrical conductivity values estimated by the NM were close to the measured values. For estimating total capillary rise over large areas, the TSAM is preferred over the NM because of its fewer input requirements and shorter execution time

Osteogenic tumour in Australopithecus sediba: Earliest hominin evidence for neoplastic disease

We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported from the type specimen of the extinct hominin Australopithecus sediba from Malapa, South Africa, dated to 1.98 million years ago. The affected individual was male and developmentally equivalent to a human child of 12 to 13 years of age. A penetrating lytic lesion affected the sixth thoracic vertebra. The lesion was macroscopically evaluated and internally imaged through phase-contrast X-ray synchrotron microtomography. A comprehensive differential diagnosis was undertaken based on gross- and micro-morphology of the lesion, leading to a probable diagnosis of osteoid osteoma. These neoplasms are solitary, benign, osteoid and bone-forming tumours, formed from well-vascularised connective tissue within which there is active production of osteoid and woven bone. Tumours of any kind are rare in archaeological populations, and are all but unknown in the hominin record, highlighting the importance of this discovery. The presence of this disease at Malapa predates the earliest evidence of malignant neoplasia in the hominin fossil record by perhaps 200 000 years.NCS201

Nucleon Structure Functions at Moderate Q**2: Relativistic Constituent Quarks and Spectator Mass Spectrum

We present a model description of the nucleon valence structure function applicable over the entire region of the Bjorken variable x, and above moderate values of Q**2 (> 1 GeV**2). We stress the importance of describing the complete spectrum of intermediate states which are spectator to the deep-inelastic collision. At a scale of 1 GeV**2 the relevant degrees of freedom are constituent quarks and pions. The large-x region is then described in terms of scattering from constituent quarks in the nucleon, while the dressing of constituent quarks by pions plays an important role at intermediate x values. The correct small-x behavior, which is necessary for the proper normalization of the valence distributions, is guaranteed by modeling the asymptotic spectator mass spectrum according to Regge phenomenology.Comment: 44 pages RevTeX, 9 uuencoded figures, accepted for publication in Nucl. Phys.