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During HIV infection, specific RNA-protein interaction between the Rev response element (RRE) and viral Rev protein is required for nuclear export of intron-containing viral mRNA transcripts. Rev initially binds the high-affinity site in stem-loop II, which promotes oligomerization of additional Rev proteins on RRE. Here, we present the crystal structure of RRE stem-loop II in distinct closed and open conformations. The high-affinity Rev-binding site is located within the three-way junction rather than the predicted stem IIB. The closed and open conformers differ in their non-canonical interactions within the three-way junction, and only the open conformation has the widened major groove conducive to initial Rev interaction. Rev binding assays show that RRE stem-loop II has high- and low-affinity binding sites, each of which binds a Rev dimer. We propose a binding model, wherein Rev-binding sites on RRE are sequentially created through structural rearrangements induced by Rev-RRE interactions. HIV relies on the RRE RNA interaction with Rev protein for nuclear export of viral mRNAs. The structure of the high-affinity Rev binding site in RRE in two conformations suggests a mechanism for initial Rev binding and oligomerization onto RRE.

Economical coiled tubing (CT) is a multipurpose tool with growing significance for many service companies in oil and gas exploration and production. From relative obscurity as a longtime niche-market provider of well service applications, CT has recently expanded to many real and proposed capabilities. Steve Jacobs of Resource Marketing says CT has great potential, but there are many opinions over which way it is headed. Joe P. Pavlich of BP Exploration says that in addition to job speed, BP operators do not have to kill the well or disturb packers or tubing, and they appreciate highly accurate placement of fluids, increased mobility, and minimum production loss. CT's major market is in workover applications. Use of various sizes of CT as the production string is another potential market, and there is growing interest in using it in continuous flow line applications. According to Jack Moseley of Nowcam, one of CT's primary limitations is that it must compete with workover rigs available at very low rates in a depressed market.

The well-service market is characterized by low rates, anemic activity, and more demanding regulators and customers. Most contractors, from dominant regional firms to small operations, are firmly mired in the US, trying to survive and adapt. The recent push toward international operations has shaken the industry's domestic customer base and driven activity down even more. The industry's overseas expansion is constrained by fewer mature fields, difficult entry into many of the markets, and the relatively uncomplicated nature of the work, which makes it easier for foreign companies to compete. Beyond the daily problems, the domestic well-service and workover (WS-WO) industry's central dilemma continues to be a matter of supply and demand. Many more WS-WO contractors must expire before the survivors can begin to prosper. In dealing with an elusive, frustrating market, contractors are changing the way they do business by adapting to new environmental and safety regulations, exploring new technologies and working with their customers in new ways.

Potassium (K) fertilizer has important yield and cost ramifications in soybean [Glycine max (L.) Merr.] production. Rate recommendations are often based on expected yield response as predicted by a soil test. To that end, soybean response to K application rate studies were analyzed using 86 site‐years from 2004 to 2019. We estimated a generic yield response curve across soybean cultivar and soil texture to allow calculation of profit‐maximizing K rates for producers in the mid‐southern United States that also consider crop value and fertilizer cost. Further, we compared profit‐maximizing fertilizer‐K rates with those currently recommended. Using a spreadsheet‐based decision aid, soybean prices and yields, fertilizer‐K cost, and a range of initial soil‐test K (STK) values, as observed over the last 10 yr, we find that current uniform fertilizer‐K rate recommendations were greater than the predicted profit‐maximizing rates. Profit‐maximizing rates added profit ranging from US $2.32 ha−1 at initial Mehlich‐3 K availability values of 110 mg K kg−1 to US$ 29.35 ha−1 at 60 mg K kg−1 on average. The corresponding fertilizer‐K rate reductions were 11 and 48 kg K ha−1, respectively, resulting in attendant yield penalties of only 28 and 52 kg ha−1. Furthermore, K fertilization was not economically justifiable beyond STK of 128 mg K kg−1 on average. Hence, performing soil tests and calculating profit‐maximizing fertilizer‐K rates showed promising returns to producers at lesser fertilizer‐K use by sacrificing a minimal amount of yield. Also, variable‐rate applied K fertilizer in comparison to uniform rate application was rarely cost effective within the tested assumptions.

To determine whether removal of default duration, embedded in electronic prescription (e-script), influenced antibiotic days of therapy. Interrupted time-series analysis. The study was conducted across 2 community hospitals, 1 academic hospital, 3 emergency departments, and 86 ambulatory clinics. Adults prescribed a fluoroquinolone with a duration <31 days. Removal of standard 10-day fluoroquinolone default duration and addition of literature-based duration guidance in the order entry on December 19, 2017. The study period included data for 12 months before and after the intervention. The study included 35,609 fluoroquinolone e-scripts from the preintervention period and 31,303 fluoroquinolone e-scripts from the postintervention period, accounting for 520,388 cumulative fluoroquinolone DOT. Mean durations before and after the intervention were 7.8 (SD, 4.3) and 7.7 (SD, 4.5), a nonsignificant change. E-scripts with a 10-day duration decreased prior to and after the default removal. The inpatient setting showed a significant 8% drop in 10-day e-scripts after default removal and a reduced median duration by 1 day; 10-day scripts declined nonsignificantly in ED and ambulatory settings. In the ambulatory settings, both 7- and 14-day e-script durations increased after default removal. Removal of default 10-day antibiotic durations did not affect overall mean duration but did shift patterns in prescribing, depending on practice setting. Stewardship interventions must be studied in the context of practice setting. Ambulatory stewardship efforts separate from inpatient programs are needed because interventions cannot be assumed to have similar effects.

BackgroundDespite high rates of comorbidity between pain and posttraumatic stress disorder (PTSD), little is known about factors that may account for this association. Previous research demonstrates that anxiety sensitivity (AS), the tendency to fear bodily sensations associated with anxious arousal, is elevated among patients with these conditions. However, no research to date has examined whether AS explains the association between pain and PTSD symptom severity.MethodsThe current sample included 115 veterans with a trauma- and stressor-related disorder (i.e., PTSD or subthreshold PTSD) presenting for psychological services to an outpatient PTSD clinic at a Veterans Affairs hospital.ResultsFindings revealed a significant association between self-reported pain and PTSD symptom severity that was indirect via AS and in particular, AS cognitive concerns.ConclusionsThese findings, though limited by their cross-sectional nature, provide support for AS as a risk factor for perceived pain and PTSD symptoms, particularly among veteran samples.

Whereas K fertilization is necessary to maximize corn (Zea mays L.) and cotton (Gossypium hirsutum L.) yields in soils with sub‐optimum K availability, maximizing yield is rarely profit‐maximizing. Estimating the tradeoff between yield and fertilizer cost using current soil‐building and/or yield‐maximizing rate recommendations vs. profit‐maximizing fertilizer‐K rates (KR*) provides insights for producers. Thirty‐nine and 24 fertilizer‐K rate trials were used to estimate respective corn and cotton yield response based on soil‐K availability (SK). Using a field's SK, yield potential, yield response to fertilizer‐K, crop price, and fertilizer‐K cost, KR* were calculated over the past 10 yr. Averaging over that period, using KR* at SK of 75 and 60 mg K kg–1 (a) reduced fertilizer‐K rate by 10 and 38 kg K ha–1, respectively, (b) decreased yield by 53 and 32 kg ha–1, respectively, and (c) increased profitability by US $1.75 and $ 34.24 ha–1, respectively, in comparison to current recommendations for corn. At SK of 75 and 110 mg K kg–1, cotton profitability at KR* vs. current recommendations rose by$11.54 to $ 25.95 ha–1, respectively, using 36 and 101 kg K ha–1 more fertilizer, respectively, which led to 27 and 73 kg ha–1 greater yield, respectively. As with prior studies for rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.], corn results suggest using less fertilizer than currently recommended, whereas for cotton, strong yield response to fertilizer‐K and relatively high crop price justified KR* that were above currently recommended rates. A spreadsheet‐based decision tool is online to offer this insight to producers and crop consultants. Core Ideas Fertilizer‐K rate recommendations often rely on yield response and soil‐test values alone. Adding crop price and K‐fertilization cost may improve the profitability of growing corn and cotton. Fertilizer‐K rates could be profitably reduced for corn producers in the U.S. mid‐South. Fertilizer‐K rates for cotton producers could be profitably raised in the U.S. mid‐South. Online decision support software may aid producers to make complex soil fertility decisions.

Potassium fertilizer represents a non‐trivial input cost in rice (Oryza sativa L.) production and its rate recommendation is often based on yield and K deficiency observations alone. However, profit‐maximizing fertilizer‐K rate not only hinges on the yield response to both initial available soil K and applied fertilizer K, but also the crop value and fertilizer cost. To that end, K application rate studies for rice, performed across 91 site‐years from 2001 to 2018, allowed estimation of a generic yield response curve to calculate profit‐maximizing K rates for producers in the mid‐southern United States. To determine whether those calculation efforts are justified, we compared profit‐maximizing fertilizer‐K rates to those currently recommended. Using rice prices and yields, fertilizer‐K cost, and a range of initial soil‐test K values, as observed over the last 10 yr, we find that current fertilizer‐K rate recommendations are too high. Profit‐maximizing rates added from US $0.88 ha−1 at initial Mehlich‐3 K availability values of 75 mg K kg−1 to $ 28.19 ha−1 at 105 mg K kg−1 on average. The corresponding fertilizer‐K reductions were 0.35 and 56 kg K ha−1, respectively, resulting in attendant yield penalties of only 4 kg ha−1 and 105 kg ha−1. Hence, performing soil tests and using decision support software to obtain profit‐maximizing fertilizer‐K rates is expected to enhance producer profit at rice yield penalties that are smaller than fertilizer cost savings. While profit‐maximizing rate recommendations do vary in a field with varying available soil K, using the mid‐range estimate rather than variable‐rate technology was deemed most feasible.

Profitability, yield, and fertilizer use are compared across three different potassium (K) fertilizer rate recommendation ideologies. Existing agronomic, “build and maintain” rate recommendations (KE) are compared to profit-maximizing rates with and without taking long-run soil-test K (STK) implications into account. Regardless of starting STK, K use equilibrated over the course of 3 years irrespective of ideology. Since taking long-run STK into account did not alter ending STK and only led to a miniscule yield effect, we encourage producers to use annual profit-maximizing K rates that were 3–11% lower than KE rates and generated more profit with minimal yield loss.