A straight cylindrical duct is considered containing an axial mean flow that is uniform everywhere except within a boundary layer near the wall, which need not be thin. Within this boundary layer the mean flow varies parabolically. The linearized Euler equations are Fourier transformed to give the Pridmore-Brown equation, for which the Green's function is constructed using Frobenius series. The critical layer gives a non-modal contribution from the continuous spectrum branch cut, and dominates the downstream pressure perturbation in certain cases, particularly for thicker boundary layers. The continuous spectrum branch cut is also found to stabilize what are otherwise convectively unstable modes by hiding them behind the branch cut. Overall, the contribution from the critical layer is found to give a neutrally stable non-modal wave when the source is located within the sheared flow region, and to decay algebraically along the duct as $O(x^{-{5}/{2}})$ for a source located with the uniform flow region. The Frobenius expansion, in addition to being numerically accurate close to the critical layer where other numerical methods lose accuracy, is also able to locate modal poles hidden behind the branch cut, which other methods are unable to find; this includes the stabilized hydrodynamic instability. Matlab code is provided to compute the Green's function.

Scanning transmission electron microscopy (STEM) allows for imaging, diffraction, and spectroscopy of materials on length scales ranging from microns to atoms. By using a high-speed, direct electron detector, it is now possible to record a full two-dimensional (2D) image of the diffracted electron beam at each probe position, typically a 2D grid of probe positions. These 4D-STEM datasets are rich in information, including signatures of the local structure, orientation, deformation, electromagnetic fields, and other sample-dependent properties. However, extracting this information requires complex analysis pipelines that include data wrangling, calibration, analysis, and visualization, all while maintaining robustness against imaging distortions and artifacts. In this paper, we present py4DSTEM, an analysis toolkit for measuring material properties from 4D-STEM datasets, written in the Python language and released with an open-source license. We describe the algorithmic steps for dataset calibration and various 4D-STEM property measurements in detail and present results from several experimental datasets. We also implement a simple and universal file format appropriate for electron microscopy data in py4DSTEM, which uses the open-source HDF5 standard. We hope this tool will benefit the research community and help improve the standards for data and computational methods in electron microscopy, and we invite the community to contribute to this ongoing project.

The Taipan galaxy survey (hereafter simply ‘Taipan’) is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z < 0.4. Taipan will use the newly refurbished 1.2-m UK Schmidt Telescope at Siding Spring Observatory with the new TAIPAN instrument, which includes an innovative ‘Starbugs’ positioning system capable of rapidly and simultaneously deploying up to 150 spectroscopic fibres (and up to 300 with a proposed upgrade) over the 6° diameter focal plane, and a purpose-built spectrograph operating in the range from 370 to 870 nm with resolving power R ≳ 2000. The main scientific goals of Taipan are (i) to measure the distance scale of the Universe (primarily governed by the local expansion rate, H0) to 1% precision, and the growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated ‘virtual observer’ software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.

Field experiments were conducted in Louisiana and Mississippi from 2011 through 2013 to evaluate crop injury, weed control, and yield in field corn following pyroxasulfone applied PRE and POST. Pyroxasulfone PRE or POST did not injure corn at any evaluation. Barnyardgrass control was not improved with the addition of any POST treatment to pyroxasulfone alone or atrazine plus pyroxasulfone PRE; however, all POST treatments increased barnyardgrass control to at least 95% at all evaluations following atrazine PRE. All treatments that contained a PRE followed by POST application controlled browntop millet ≥90% at all evaluations. All POST treatments increased ivyleaf morningglory control to ≥92% following atrazine or pyroxasulfone alone PRE. However, control with atrazine plus pyroxasulfone PRE was similar or greater 28 d after POST than all treatments that received a POST application. In the absence of a POST treatment, pyroxasulfone or atrazine plus pyroxasulfone PRE controlled Palmer amaranth 93 to 96% at all evaluations, but atrazine alone PRE provided 84, 82, and 66% control 7, 14, and 28 d after POST, respectively. All programs that contained a PRE followed by POST herbicide treatment controlled Palmer amaranth >90% at all evaluations. Corn yield following all treatments except atrazine alone PRE and the nontreated were similar and ranged from 10990 to 12330 kg ha−1. This research demonstrated that pyroxasulfone can be a valuable tool for weed management in a corn weed management program.

Cultivar and/or application of early-season (starter) nitrogen (N) fertilizer may influence rice tolerance to clomazone. Field studies were conducted to compare the response of hybrid and inbred rice cultivars to applications of clomazone and starter N fertilizer treatments. The inbred cultivar ‘Cocodrie’ and the hybrid cultivar ‘XL723’ were treated with clomazone at 0, 420, or 672 g ai ha−1 immediately after seeding, and starter N fertilizer was applied at 0 or 24 kg N ha−1 when rice reached the two-leaf growth stage. Pooled across clomazone rates and starter N fertilizer treatments, height of Cocodrie 1 week after emergence (WAE) was greater than that of XL723 in 1 of 3 yr. The difference in height between Cocodrie and XL723 resulted from greater clomazone injury 1 WAE on XL723 compared with Cocodrie. No differences in rice height 3 WAE were detected between Cocodrie and XL723 in 2 of 3 yr. when data were pooled across clomazone rates and starter N fertilizer treatments. Injury 3 WAE was similar for Cocodrie across the 3 yr., but injury on XL723 was greater in 1 of 3 yr. Rough rice yield was lower in plots treated with either rate of clomazone where no starter N fertilizer treatment was applied; however, in plots receiving a starter N fertilizer treatment, no effect of clomazone rate on rough rice yield was observed. Clomazone rate did not influence rough rice yield of Cocodrie in any single yr., but rough rice yields of XL723 were lower in plots receiving clomazone compared with plots that received no clomazone in 1 of 3 yr. Therefore, differential susceptibility to clomazone between Cocodrie and XL723 exists based on early-season response and rough rice yield. Starter N fertilizer treatments were beneficial for overcoming yield reductions due to clomazone injury.

Four field experiments were conducted in Louisiana and Mississippi in 2009 and 2010 to evaluate POST herbicides treatments with tembotrione applied alone or as a prepackaged mixture with thiencarbazone for weed control in corn. Treatments included tembotrione at 92 g ai ha−1, thiencarbazone : tembotrione at 15 : 76 g ai ha−1, atrazine at 2,240 g ai ha−1, glufosinate at 450 g ai ha−1, glyphosate at 860 g ae ha−1, and coapplications of tembotrione or thiencarbazone : tembotrione with atrazine, glufosinate, or glyphosate. All treatments were applied to 26-cm corn in the V4 growth stage. Treatments containing thiencarbazone : tembotrione and those with tembotrione controlled barnyardgrass, browntop millet, entireleaf morningglory, hophornbeam copperleaf, johnsongrass, Palmer amaranth, and velvetleaf 85 to 96% and 43 to 97% 28 d after treatment and at corn harvest, respectively. Corn yield ranged from 9,200 to 10,420 kg ha−1 and was greater than the nontreated control following all herbicide treatments, except atrazine alone. Results indicated that thiencarbazone : tembotrione or tembotrione POST is an option for weed management in corn, and applications of thiencarbazone : tembotrione would be strongly encouraged where rhizomatous johnsongrass is problematic.

Field studies were conducted in Louisiana and Mississippi in 2009 and 2010 to evaluate coapplications of glyphosate, pyrithiobac, and residual herbicides on growth and yield of glyphosate-resistant cotton. Treatments were a factorial arrangement of glyphosate (0 and 860 g ae ha−1), pyrithiobac (0 and 470 g ai ha−1), and two residual herbicides (pendimethalin [1,120 g ai ha−1], S-metolachlor [1,070 g ai ha−1], and no residual herbicide). Cotton injury was greatest 3 d after treatment (DAT) and decreased at each evaluation interval until 28 DAT when pyrithiobac was coapplied with glyphosate. Cotton injury ranged from 4 to 17% through 14 DAT when pyrithiobac was applied alone (no residual herbicide) or with pendimethalin, but injury decreased to ≤ 3% after 14 DAT. Cotton injury 3 to 21 DAT following pyrithiobac plus S-metolachlor ranged from 4 to 31%, but S-metolachlor alone injured cotton 1 to 7%. When pyrithiobac was included, cotton injury following S-metolachlor was 3 to 15% greater than that following pendimethalin from 3 to 14 DAT. Pendimethalin did not reduce plant height at 21 or 42 DAT compared with treatments receiving no residual herbicide, but S-metolachlor reduced plant heights 5 and 4% at 21 and 42 DAT, respectively. Although cotton injury was severe in some cases and persisted until 21 DAT, the injury did not cause reductions in yield. This indicates the early-season cotton injury was transient, and cotton was able to recover from the injury with no observed differences in yield.

Research was conducted in 2012 and 2013 to evaluate the response of the rice cultivars ‘Cheniere', ‘CL151′, ‘Caffey', ‘CL261′, and ‘CLXL745′ response to POST applications of saflufenacil. Treatments included a nontreated control, saflufenacil at 50 g ai ha−1, and carfentrazone at 35 g ai ha−1 applied mid-POST (MPOST) to rice in the three- to four-leaf stage. Pooled across cultivars, injury was greatest at 3 and 7 d after treatment (DAT), 21 and 17%, respectively. Rice injury was only 5% at 14 DAT and 1% at 28 DAT. Hybrid long-grain cultivar CLXL745 was injured more than inbred long-grain cultivars CL151 and Cheniere. Cheniere was more tolerant than inbred medium-grain cultivars CL261 and Caffey. All cultivars exhibited tolerance to saflufenacil as evidenced by similar normalized difference vegetative index (NDVI), maturity, mature plant height, and rice yield (rough, whole, and total milled rice).

Palmer amaranth is the most common and troublesome broadleaf weed species of rice in Mississippi because of the effects of early-season interference and infestations on rice levees, and herbicides for residual or POST control of Palmer amaranth in rice are limited. Three studies were conducted in 2012 and 2013 to evaluate application rates and timings of saflufenacil in rice and to determine the influence of adjuvants when mixed with saflufenacil applied POST. In a PRE study, no injury occurred after saflufenacil PRE, and no control was observed from carfentrazone. Hemp sesbania and Palmer amaranth control increased with increasing saflufenacil rate when applied PRE. Hemp sesbania control with saflufenacil at any rate PRE was ≤ 25% at 35 d after treatment (DAT). Palmer amaranth and ivyleaf morningglory control with saflufenacil at 75 g ai ha−1 PRE was ≥ 94% 35 DAT. In a POST study, rice injury was influenced by application timing and rate of saflufenacil; however, efficacy was not. Rice injury with saflufenacil at 25 g ha−1 and carfentrazone early POST (EPOST) and late POST was similar 7 DAT. Saflufenacil at 50 and 75 g ha−1 EPOST were the most injurious 7 DAT. Control of hemp sesbania and ivyleaf morningglory was similar for all rates of saflufenacil and carfentrazone; however, Palmer amaranth control with saflufenacil at any rate was greater than that of carfentrazone 14 and 28 DAT. In an adjuvant study, rice injury was influenced by adjuvant and saflufenacil rate. Saflufenacil applied alone or in mixture with crop oil concentrate (COC) was least injurious, and saflufenacil at 50 g ha−1 was more injurious than saflufenacil at 25 g ha−1. Saflufenacil applied in combination with any adjuvant provided better control of hemp sesbania and Palmer amaranth than saflufenacil alone. On the basis of this research, saflufenacil should be applied PRE at 50 or 75 g ha−1, depending on weed spectrum, and POST applications should be made at 25 g ha−1 in combination with COC after the two-leaf rice growth stage.

Research was conducted in Mississippi in 2012 and 2013 to compare the efficacy of saflufenacil to other broadleaf herbicides applied in mixtures with imazethapyr in a Clearfield rice system. Saflufenacil at 50 g ai ha−1, carfentrazone at 35 g ai ha−1, a prepackaged mixture of halosulfuron plus thifensulfuron at 35 plus 4 g ai ha−1, and a prepackaged mixture of propanil plus thiobencarb at 2,240 plus 2,240 g ai ha−1 were applied in mixture with imazethapyr at 70 g ai ha−1 early-POST (EPOST) to rice in the one- to two-leaf stage or late-POST (LPOST) to rice in the four-leaf to one-tiller stage. No differences in injury among the broadleaf herbicides or between application timings were detected at any evaluation. Imazethapyr combined with propanil plus thiobencarb or saflufenacil provided the greatest control of barnyardgrass 7 and 14 d after treatment (DAT). Hemp sesbania, ivyleaf morningglory, and Palmer amaranth control was greatest and similar for imazethapyr combined with carfentrazone, propanil plus thiobencarb, and saflufenacil; however, rough rice yield was greatest for imazethapyr combined with propanil plus thiobencarb or saflufenacil. Propanil plus thiobencarb or saflufenacil can be used in a Clearfield rice system to achieve optimum weed control and highest rice yields.

Dense populations of glyphosate-resistant (GR) Italian ryegrass are problematic for spring burndown herbicide programs and crop establishment in the midsouthern United States. Two field studies were conducted to evaluate fall-applied residual herbicides for control of GR Italian ryegrass and to identify the most effective application timing for these herbicides. Fall applications of clomazone at 0.84 and 1.12 kg ai ha−1, pyroxasulfone at 0.16 kg ai ha−1, and S-metolachlor at 1.79 kg ai ha−1 controlled GR Italian ryegrass ≥ 93% 180 d after application. Control from incorporated applications of pendimethalin at 1.59 kg ai ha−1 and trifluralin at 1.68 kg ai ha−1 and surface applications of S-metolachlor at 1.42 kg ha−1 provided control similar to the best treatments. Glyphosate-resistant Italian ryegrass control following clomazone, pyroxasulfone, S-metolachlor, or trifluralin applied in mid September, October, or November exceeded that from fall tillage by 19 to 56% at 90 and 140 d after the last treatment. Pyroxasulfone and S-metolachlor controlled more GR Italian ryegrass following October or November applications compared with those in September at both 90 and 140 d after the last application timing. However, the benefit of delaying clomazone application from October to November was not realized until the last evaluation (140 d after the last treatment). Clomazone, pyroxasulfone, and S-metolachlor offer growers the best opportunity for residual control of GR Italian ryegrass, and control is optimized when these herbicides are applied in November.