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We clarify the physical origin and meaning of the two-dimensional relativistic densities of the light front formalism. The densities are shown to originate entirely from the use of light front time instead of instant form time, which physically corresponds to using an alternative synchronization convention. This is shown by using tilted light front coordinates, which consist of light front time and ordinary spatial coordinates, and which are also used to show that the obtained densities describe a system at rest rather than at infinite momentum. These coordinates allow all four components of the electromagnetic current density to be given clear physical meanings. We explicate the formalism for spin-half targets, obtaining charge and current densities of the proton and neutron using empirical form factor parametrizations, as well as up and down quark densities and currents. Angular modulations in the densities of transversely-polarized states are explained as originating from redshifts and blueshifts due to quarks moving in different longitudinal directions., 26 pages, 7 figures

We obtain the energy-momentum tensor (EMT) in the 't Hooft model of two-dimensional quantum chromodynamics. The EMT is decomposed into contributions from quark and gluon fields, with all of the (plus component of) the light front momentum being carried by the quark field. The energy is split between quark and gluon fields, with the gluon field carrying the self-energy of the dressed quarks. We consider the pion in the limit of small but non-zero quark masses -- which has previously withstood numerical treatment -- as as a concrete example. We solve for the pion wave function using a variational method and obtain numerical results for its energy breakdown into quark and gluon contributions., Comment: 10 pages, 4 figures

Estimation of crack depths and spacing due to desiccation of clayey soils is needed to predict changes in mechanical or hydraulic properties in the cracked layer. These changes affect the infiltration of water, stability, and deformation of a soil mass. Desiccation cracks are associated with increasing suction due to moisture loss accompanied by restrained shrinkage, which results in tensile stresses in near surface soil layers. Cracks propagate when the developed tensile stresses exceed the tensile strength of soil. A simple analytical method is presented to predict crack depths in compacted clayey soil due to changes in matric suction with depth. The model equation is based on the Hookean elastic equation relating incremental strain to incremental stress and incorporates two stress state variables including net normal stress and matric suction. Input to the model equation includes the tensile strength and elastic parameters, and to complete the prediction of crack depth, the suction change profile of interest is needed. The method validity was investigated by comparing predicted crack depths to those observed in soil compacted in a bench scale apparatus for studying desiccation cracking. Tensile strength and elastic properties were determined from tests conducted on soil during desiccation under approximate uniaxial conditions. Predicted crack depths were obtained based on changes in suction interpreted from water content sensors at various depths in the soil bed and compared favorably to observed desiccation crack depths.

Many Pythium spp. are causal agents of diseases of turfgrasses. Pythium spp. disseminate through irrigation systems in agricultural settings, and this study provides evidence that Pythium spp. also disseminate through golf course irrigation. Water samples were collected from irrigation heads and water sources at 10 golf courses in Missouri and Kansas, U.S.A. Samples were collected from 2018 to 2019 in April, July, and October. Phosphorus, nitrogen, and chloride concentrations were measured from irrigation head samples to determine if these parameters influence frequency of Pythium spp. detected. Pythium spp. were detected in samples through baiting and membrane filtration. Cultures were isolated on PARP media, and DNA was extracted from putative Pythium isolates. The internal transcribed spacer region was PCR-amplified and sequenced. Phylogenetic trees were constructed using representative sample sequences, sequences from seven morphologically identified reference isolates of Pythium, and similar GenBank accessions. Detected oomycete species include Lagenidium giganteum, Pythium biforme, Pythium insidiosum, Pythium marsipium, Pythium plurisporium, and Saprolegnia hypogyna. Twenty-one clades lacked species-level resolution, and 14 of these clades were associated with Pythium species. Clades A, C, D, E, I, and M contain Pythium species that cause root and crown rot on creeping bentgrass. Detected Pythium communities were dependent on the detection method used and sampling source. Pythium frequency and diversity were highest in April 2019. Sample temperature, sampling site, and chloride and nutrient concentrations did not influence Pythium frequency in samples. Irrigation systems using surface water sources contained at least three Pythium spp. over the course of 2 years.

Nuclear super-allowed $β$ decay has been used to obtain tight limits on the value of the CKM matrix element $V_{ud}$ that is important for unitarity tests, and therefore important for tests of the standard model. Current requirements on precision are so intense that effects formerly thought too small to matter are now relevant. This article is a brief review of personal efforts to include the effects of strong interactions on Fermi $β$ decay. First I examine the role of isospin violation in the decay of the neutron. The size of the necessary correction depends upon detailed strong-interaction dynamics. The isospin violating parts of the nucleon wave function, important at the low energy of $β$ decay, can be constrained by data taken at much higher energies, via measurements, for example, of $ed\to e'π^\pm +\rm X $ reactions at Jefferson Laboratory. The next focus is on the role of nuclear short-ranged correlations, which affect the value of the correction needed to account for isospin violation in extracting the value of $V_{ud}$. The net result is that effects previously considered as irrelevant have become relevant for both neutron and nuclear $β$ decay., 7 pages, no figures, Prepared for a Special Issue of the journal Universe on the general subject of neutron lifetime determination. arXiv admin note: text overlap with arXiv:2201.10651

The influence of nucleon-nucleon short-ranged correlations (SRC) on nuclear super-allowed $\beta$ decay is examined. The need for this is driven by the observed depletion of spectroscopic strength obtained in studies of $(e,e')$ and $(d,^3{\rm He})$ reactions on a wide variety of nuclei. We show that the influence of SRC is model-dependent, but may be very substantial. The $^{46}$V nucleus is used as an example. The resulting impact on studies of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element is discussed., Comment: 7 pages, 0 figures. Several improvements in this version

A formalism for the study of charge symmetry breaking (CSB) effects is discussed and used to analyze the effects of charge symmetry breaking on neutron beta decay. The effect of including CSB reduces the beta decay matrix element by an amount on the order of $10^{-4}$, a value much larger than the previous estimate. A much smaller contribution due to proton recoil is treated as well, which is found to be on the order of $10^{-6}$. The current uncertainty in the value of $V_{ud}$ is also of order $10^{-4}$. An improvement of that uncertainty by an order of magnitude would require that charge symmetry breaking effects should be included in future analyses., 8 pages, submitted to add citation

Spread footings are often supported in the upper zone of the soil profile, which is frequently unsaturated. It is common in geotechnical practice to use in situ testing to assess soil properties throughout the zone of influence for footings. These tests regularly include the Standard Penetration Test (SPT), and sometimes the Cone Penetration Test (CPT), and Pre-bored Pressuremeter Test (PMT). Yet degree of saturation is often not considered in the analysis of the test results. To investigate the importance of partial saturation, SPTs, CPTs, and PMTs were conducted at two test sites over two years covering dry and wet periods. Water content and suction profiles were established for each test date to assess their impact on the in situ tests. Results from this study revealed that changes in moisture content and suction had an important influence on the results of in situ tests and the soil parameters derived from these tests. Specifically, undrained shear strengths estimated from SPT penetration resistance and CPT tip resistance using empirical and semi-empirical equations, respectively, were significantly lower during wet periods compared to dry periods. Consequently, estimated bearing capacities for a shallow foundation varied considerably from dry to wet periods. Similarly, PMT limit pressures were significantly impacted by increases in moisture content. Associated reductions in limit pressures resulted in large reductions in predicted allowable bearing capacity. While PMT modulus did appear to decrease with increasing moisture, its impact on settlement was offset by the decrease in allowable bearing pressure under wet conditions.

The Upper Mississippi River flows approximately 2000 km from Lake Itasca, Minnesota to Cairo, Illinois where it is confluences with the Ohio River to form the Lower Mississippi River. North of the confluence, numerous snags, sand bars, rapids, and other obstructions made the Upper Mississippi River travel difficult. This paper highlights how the geological and landscape resources of the Upper Mississippi River and tributary watershed were responsible for the successful economic development of this historically rich region of North America. Environmental challenges include an attempt to keep invasive species such as the Asian carp out of the rivers and lakes north of the Twin Cities. In an attempt to protect the Mississippi River resource, Environmental and Conservation groups have opposed continued navigation through Minneapolis and St. Paul and the planned Upper Mississippi River navigation infrastructure restoration by the United States Corps of Engineers including the upper and lower St. Anthony locks and dams. These Environmental, Conservation and Save the River groups are attempting to mitigate the historic highest and best use of the Mississippi River and adjacent watershed, navigation, and economic development, by having the urban river restored to the natural state.

Suction-controlled interface direct shear tests were conducted on textured and smooth HDPE geomembrane counterfaces in contact with lean clay. Soil samples were compacted wet of optimum to simulate placement conditions in a composite liner. Tests on saturated samples and soil only were conducted for comparison. Additionally, limited testing was conducted to study the effect of shearing rate on the results. Results reveal that matric suction provided increased shearing resistance, compared to the saturated case, for the textured and smooth geomembrane interfaces, and the extended Mohr-Coulomb envelope provided a good model for geomembrane interface strength. However, strength increases were relatively small compared to soil only, particularly for the smooth interface. Total and water volume changes during shearing were significantly different for unsaturated and saturated conditions. Water volume changes during shearing in saturated soil and interfaces corresponded directly to volume change tendencies during shearing; however, for unsaturated soils this was not the case. Shearing displacement rate was observed to have a profound effect on the shearing resistance of textured geomembranes but had little apparent influence on the smooth geomembrane. Results of this study provide great insight into the unsaturated shearing behavior of clay-geomembrane interfaces and important data for development of constitutive models.

The St. Lawrence Seaway connects Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario to the Atlantic Ocean. The lakes and connecting rivers, St. Mary’s, St. Claire, Detroit, Niagara and St. Lawrence, have been a major artery for transportation, migration and trade. The Menominee River flows into Green Bay and Lake Michigan and connects to the St. Lawrence Seaway. The Great Lakes have been sailed for trading and commercial purposes since at least the 17th century. Approximately 6000 ships have sunk killing more than 30,000 sailors and passengers. Cold Canadian winds over the three Western Great Lakes pick up moisture when the lakes are not yet frozen and create snow belts in the states of Wisconsin, Michigan and in Ontario, Canada. The Western Great Lakes moderate the seasonal temperatures as they absorb heat and cool the air in the summer. The lakes radiate heat in the fall. This temperature buffering creates fruit belts further north of where the fruit is traditionally grown. During the 1950s and 1960s all of the Agent Blue, the arsenic containing herbicide used in Vietnam War, was manufactured on the banks of the Menominee River by the Ansul Company at Marinette, Wisconsin. The groundwater and the river bottom are now heavily contaminated with arsenic compounds that were released from 1957 to 1977 by Ansul as a result of the manufacture of the herbicide. The linkage of Lake Michigan to the Mississippi River has allowed Chicago’s wastewater to be disposed of into the tributaries of the Illinois River and Mississippi River to avoid contaminating Lake Michigan the source of Chicago’s drinking water. An unintended consequence of linking the Western Great Lakes basin with the Mississippi River basin was the creation of the wet pathway (Chicago Sanitary and Ship Canal) through which the flying Asian carp is trying to use to get into the Great Lakes. An electric fish barrier was constructed on the Chicago Sanitary and Ship Canal in an attempt to prevent the carp from migrating into Lake Michigan, the Great Lakes basin and the St. Lawrence Seaway. The Western Great Lakes shorelines are actively eroding partly as a consequence of the high surface water levels. In June of 2020 Lake Michigan, Lake St. Claire and Lake Huron experienced the highest water level ever recorded since the 1800s. The high risk erosion areas are retreating at the average rate of 30 cm per year for the last 15 years. Planned urban development in a high risk area helps to prevent the loss of buildings. Locating structures back from lake bluffs promotes natural shorelines and reduces the need for engineered shore protection. Erosion of the sediment under the Mackinac Bridge and pipeline has occurred. The pipeline which carries 87 million liters of oil per day between Sarnia, Ontario and Superior, Wisconsin is at risk.

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The pion cloud is important in nuclear physics and in a variety of low-energy hadronic phenomena. We argue that it is natural to expect it to also be important in lepton-proton deep inelastic scattering and Drell-Yan studies of proton structure. We compute the necessary consequences of the pion cloud in connection with the recent SeaQuest data. The effects are detailed by using the exact kinematics of the experiment. Good agreement with the measurements is obtained. Thus the universality of pionic effects is understood., 8 pages, 5 figures. Expanded discussion, added references. This version accepted for publication. arXiv admin note: text overlap with arXiv:1712.05814

A recent experiment by D. Bhetuwal et al. [Phys. Rev. Lett. 126, 082301 (2021)] used the $(e,{e}^{\ensuremath{'}}p)$ reaction on $^{12}\mathrm{C}$ to search for the effects of color transparency (the absence of final-state interactions). Color transparency was said to be ruled out. Observing the effects of color transparency depends on the ability of a putative point-like-configuration (PLC), formed in a high-momentum transfer coherent reaction, to escape the nucleus without expanding its size. We study the expansion aspect of color transparency using superconformal baryon-meson symmetry and light-front holographic QCD. A new formalism is obtained and used to analyze the recent experiment. The resulting conclusion is that effects of expansion would not be sufficiently significant in causing final-state interactions to occur. Therefore, we conclude that a PLC was not formed. This means that the Feynman mechanism involving virtual photon absorption on a single high-momentum quark is responsible for the high-momentum electromagnetic form factor of the proton.