High Tunnel Research Articles

Improvement of crop production in controlled environment agriculture through breeding

Controlled environment agriculture (CEA) represents one of the fastest-growing sectors of horticulture. Production in controlled environments ranges from highly controlled indoor environments with 100% artificial lighting (vertical farms or plant factories) to high-tech greenhouses with or without supplemental lighting, to simpler greenhouses and high tunnels. Although food production occurs in the soil inside high tunnels, most CEA operations use various hydroponic systems to meet crop irrigation and fertility needs. The expansion of CEA offers promise as a tool for increasing food production in and near urban systems as these systems do not rely on arable agricultural land. In addition, CEA offers resilience to climate instability by growing inside protective structures. Products harvested from CEA systems tend to be of high quality, both internal and external, and are sought after by consumers. Currently, CEA producers rely on cultivars bred for production in open-field agriculture. Because of high energy and other production costs in CEA, only a limited number of food crops have proven themselves to be profitable to produce. One factor contributing to this situation may be a lack of optimized cultivars. Indoor growing operations offer opportunities for breeding cultivars that are ideal for these systems. To facilitate breeding these specialized cultivars, a wide range of tools are available for plant breeders to help speed this process and increase its efficiency. This review aims to cover breeding opportunities and needs for a wide range of horticultural crops either already being produced in CEA systems or with potential for CEA production. It also reviews many of the tools available to breeders including genomics-informed breeding, marker-assisted selection, precision breeding, high-throughput phenotyping, and potential sources of germplasm suitable for CEA breeding. The availability of published genomes and trait-linked molecular markers should enable rapid progress in the breeding of CEA-specific food crops that will help drive the growth of this industry.

Preparation of sandwich-structured V6O13via direct current magnetron sputtering for high-capacity zinc-ion batteries.

Aqueous zinc-ion batteries are an appealing electrochemical energy storage solution due to their affordability and safety. Significant attention has been focused on vanadium oxide cathode materials for ZIBs, owing to their high specific capacity, unique layered or tunnel structures, and low cost. Compared to traditional methods for preparing and assembling electrode materials, direct current (DC) magnetron sputtering allows direct synthesis and uniform deposition on current collectors, offering advantages such as simplicity, mild reaction conditions, and strong film adhesion. Therefore, we synthesized sandwich-structured vanadium oxides (V6O13) with a V-O framework on stainless steel using this method, and for the first time, employed them as cathode materials for zinc-ion batteries. The unique crystal structure of V6O13 features numerous ion diffusion channels, providing ample sites for zinc ion embedding. Additionally, the multiple valence states of vanadium in V6O13 contribute to its high specific capacity and excellent coulombic efficiency during the charge/discharge process. The V6O13 synthesized at 400 °C in 3% O2 exhibits the highest specific capacity (550 mA h g-1 at 100 mA g-1). This synthesis strategy demonstrates significant application potential and offers a new pathway for the fabrication of other oxide thin-film electrode materials.

First Report of Bacterial Wilt of Ginger Caused by Ralstonia pseudosolanacearum in the Continental United States.

Ginger (Zingiber officinale) is an herbaceous perennial in the Zingiberaceae family grown primarily in tropical to subtropical biomes as a culinary spice, a traditional medicine, and a landscaping plant. While ginger grows at soil temperatures above 20°C, several farmers in the upper Midwestern US farmers grows short-season ginger in high tunnels. In 2023 and 2024, growers in southeastern Minnesota reported a new disease of ginger. USDA traced the origin of the ginger rhizomes imported by these growers to Peru (Soto-Heredia et al., 2024). Plants exhibited wilting, chlorosis, pseudostem collapse, and plant death. Rhizomes were squishy with a fetid, rotting odor. Disease incidence ranged from scattered plants to 50% of the crop. Symptomatic samples tested positive for Ralstonia solanacearum species complex (RSSC) using AgDia ImmunoStrips. Rhizome tissue extracts plated onto CPG + 1% tetrazolium chloride agar and mSMSA agar produced irregular, round-to-fluidal white colonies with pink centers after 48 h of incubation at 28°C (Kelman 1954; Engelbrecht 1994). Diagnostic RSSC phylotype-specific multiplex PCR primers Nmult21:1F, Nmult21:2F, Nmult23:AF, Nmult22:InF, Nmult22:RR, and 759f/760r confirmed isolate identity; two isolates (UMN24-1, UMN24-2) yielded bands at 280 bp and 144 bp, identifying them as RSSC and phylotype I respectively (Fegan and Prior 2005; Opina et al. 1997). Additionally, 16S rRNA PCR of these isolates was sequenced using primers 27F (5'-AGAGTTTGATCMTGGCTCAG-3')/1492R (5'-TACGGYTACCTTGTTACGACTT-3') and shared >99% identity (isolate UMN24-1: 99.00% 27F, 99.53% 1492R; UMN24-2: 99.32% 1492R) with R. pseudosolanacearum (Rps) strain Gj707 (GenBank CP104497.1). Eight ginger plants in individual pots were grown in a Conviron growth chamber (28°C, 250 μmol/m2/s, 16 h photoperiod) and inoculated at the six-leaf stage (6 weeks old) by pipetting 109 CFU of the isolate, UMN24-1, suspended in sterile water into a 30°angled 1 cm incision on the pseudostem. We scored disease incidence based on wilted leaves per total leaves on each plant for 14 days post inoculation (dpi). While control plants remained healthy, inoculated plants showed symptoms (wilting, vascular discoloration, chlorosis) at 4 dpi, were 100% wilted by 6 dpi, and all pseudostems completely collapsed by 11 dpi (Fig. S1). Bacteria recovered from the inoculated plants matched the original isolate in appearance and positively identified as RSSC phylotype I using the PCR analyses described above. To confirm taxonomic identification of UMN24-1, the complete genome of this isolate was sequenced using hybrid Illumina and Oxford Nanopore sequencing (NCBI BioProject ID PRJNA1178296, release date upon publication) (Fig. S2). Average nucleotide identity (ANI) analysis of UMN24-1 using KBase's FastANI app reported 99.8% identity shared with Japanese RSSC phylotype I strain MAFF311693 (GenBank GCF 015698385.1). We also sequenced UMN24-2, and its phylogenetic analysis revealed that the two isolates are clonal (Fig. S2). Hence, we did not submit its sequence to the NCBI. This marks the first documented case of Rps in ginger in the United States. Similar to bacterial wilt in ginger closely related crop like turmeric has been repeatedly reported in northern Europe in recent years (EPPO 2024). While RSSC phylotype I is geographically limited by its minimal cold tolerance, the emergence of a pathogen with a potentially broad host range has worrying implications in a changing climate.

Tunnel barriers for Fe-based spin valves providing high spin-polarized current.

Employing density functional theory for ground state quantum mechanical calculations and the non-equilibrium Green's function method for transport calculations, we investigate the potential of CdS, ZnS, Cd3ZnS4, and Zn3CdS4 as tunnel barriers in magnetic tunnel junctions for spintronics. Based on the finding that the valence band edges of these semiconductors are dominated by pz orbitals and the conduction band edges by s orbitals, we show that Δ1 symmetry filtering of the Bloch states in magnetic tunnel junctions with Fe electrodes results in high tunneling magnetoresistances and high spin-polarized current (up to two orders of magnitude higher than in the case of the Fe/MgO/Fe magnetic tunnel junction).

Gate-controllable two-dimensional transition metal dichalcogenides for spintronic memory

Rapid technological advancement has increased the demand for high-speed, low-power devices, particularly applied in artificial intelligence (AI) and the Internet of Things (IoT). Limitations of traditional memory devices underscore the urgency for high-performance, energy-efficient memory technologies. On the other hand, developing two-dimensional (2D) material-based devices is indispensable for next-generation memory and three-dimensional integration circuit (3D-IC) systems. Here, we propose a gate-controllable spin valve utilizing transition metal dichalcogenides (TMDs) to meet the urgent need. A high tunneling magnetoresistance (TMR) of over 4000% can be reached in reading with the help of the controlled gate. Moreover, under ungated conditions, a giant spin current density with an ultralow power consumption of 80 μW and a high spin-polarized ratio of 0.9 can be achieved, enabling high-speed and energy-efficient switching during writing. According to our design, the gate-controllable system can prevent undesired mixed reading and writing operations. Our results highlight TMDs as a promising material in spintronic memory devices.

Agronomic and Post-Harvest Performance of Strawberry Cultivars in High Tunnel and Open-Field Environment in Southeast Virginia

ABSTRACT This study evaluated crop yield potential, season extension, and post-harvest parameters of strawberry cultivars grown in open-field and high tunnel, annual hill production systems. Tested cultivars included “Albion,” “Camino Real,” “Chandler,” “Merced,” “Rocco,” “Ruby June,” “San Andreas,” and “Sweet Ann.” Strawberry plugs were transplanted in the first week of October 2019. The harvest period in the high tunnel was January 2020 through June 2020, while the harvest period in the open-field was April 2020 through June 2020. Except for “Albion” (474 g/plant) having low yield, most cultivars had similar total yields in the high tunnel. “Chandler,” “Rocco” and “Sweet Ann” had the greatest total yields in the open-field (~870 to 780 g/plant). “Albion,” “Merced,” “Ruby June,” “San Andreas” and “Sweet Ann” had the greatest fruit weights in each environment. “Camino Real” and “Ruby June” had the firmest fruit in both environments. In addition, “Merced” produced firm fruits under a high tunnel environment. “Rocco,” and “Ruby June,” had the greatest total soluble solids (~8.7 °Brix) and titratable acidity (>1.85%) in the high tunnel. Total soluble solids for most cultivars were similar in open-field environments. Titratable acidity was greatest (>1.68%) for “Albion,” “Chandler,” “Rocco” and “Ruby June” in open-field production. Different cultivars offered slightly different market-desirable traits. Although the high tunnel system extended the season, achieving marketable yield in high tunnel is challenging due to various biotic and abiotic stresses. Principal component analysis indicated that a more moderate plant size may deliver a greater proportion of large, marketable berries.

A predictive model for electrical conductivity of polymer carbon black nanocomposites

AbstractAlthough many studies have investigated the percolation threshold and conductivity in the polymer carbon black (CB) nanocomposites (PCBs) by experimental data, the modeling in this field is a topic previously overlooked in literature. This paper suggests a simple equation for percolation threshold in PCBs by the surface properties of polymer and CB a well as interphase depth (t). Also, the electrical conductivity of PCBs is simulated by CB radius (R), tunneling distance (λ) and interphase depth. The offered model is validated by experimented findings of numerous samples and parametric examinations. A thicker interphase and a higher interfacial tension positively reduce the percolation onset. The smaller CBs, lower percolation threshold, and smaller tunnels enhance the electrical conductivity of PCBs. The low percolation threshold of 0.01 is obtained by the low R (15 nm) and the thick interphase (35 nm). Also, R = 15 nm and t = 35 nm maximize the PCB conductivity to 6 S/m. These results signify the important roles of CB radius and interphase depth in the percolation threshold and conductivity of PCBs. In addition, network fraction (f) of 0.7 and λ = 1 nm produce the uppermost PCB conductivity of 1.6 S/m, but the system is insulated at CB network fraction less than 0.35 or tunneling distance more than 2 nm. Therefore, high network fraction and low tunneling distance are needed to enhance the conductivity of PCBs.Highlights An equation for percolation onset of PCBs is proposed by CB radius and interphase depth. The offered model is validated by experimented data and parametric examinations. A thicker interphase and a higher interfacial tension positively reduce the percolation onset. Smaller CBs, lower percolation onset, and smaller tunnels enhance the PCB conductivity. CB radius and interphase depth significantly manage the conductivity of PCBs.

Usability of 'Pink Pearl' 'Aiolos' and 'Blue Jacket' Hyacinth (Hyacinthus orientalis L.) varieties with Pre- and Postharvest Boric Acid Application as Cut Flowers

The study aimed to investigate the effect of boric acid (BA) treatments on availability of 'Pink Pearl' 'Aiolos' and 'Blue Jacket' hyacinth varieties as cut flower. For this purpose, 0, 50, 100 and 150 ppm boric acid doses were applied to hyacinths in pre- and post- harvest period. Boric acid (BA) was sprayed to leaves before harvest, while mixed into vase solution after harvest. The potted hyacinth plants were placed in a high plastic tunnel after stratification. The temperature in plastic tunnel kept at 18-20 oC during the cultivation. Pre-harvest treatments were performed as spraying prepared BA solutions to the leaves when the leaves reached to full size. During the vegetation period, the qualitative and quantitative parameters such as total leaf number, spike stalk length, leaf color (L* and hue (ho)), leaf chlorophyll (SPAD) value, total floret number, leaf length, total plant length, and total blooming spike number were measured. After harvest, hyacinth plants were placed in vase solution and monitored for post-harvest strength under 12 hours light/12 hours dark photoperiod conditions. Water uptake, the spike stalk length, and the vase longevity of the spike were observed during the vase life period. The BA treatments did not show any significant effect on the vase life of the hyacinth spike. The 150-ppm BA, however, improved leaf quality by increasing leaf chlorophyll and ho values while decreasing L* values. In conclusion, it can be suggested that the ‘Aiolos’ cultivar has a potential as cut flower due to its longer plants and flower stems both in pre- and post-harvest period, as well as its longer vase life. Among the BA applications, it was concluded that the 100 ppm application is a viable option for increasing water uptake and reducing weight loss during the vase period.

An Assessment of Geotechnical Characteristics of Gharraf Oil Field Area Using Electrical Resistivity Test

Abstract Geotechnical characteristics of soil are very important for civil applications and engineers because the structures almost construct and built on the ground such as high buildings, towers, bridges, tunnels and others on the soils. Electrical resistivity (ER) measurements are nowadays widely used to evaluate the geotechnical characterization of soil as they are fast, time-consuming and costly and non-destructive. This article provides the data of soil electrical resistivity measurements carried out on different zones and sites in Gharraf oil field area (northwestern part of the Thi-Qar governorate in the south east of Iraq). In this study the analyses of the obtained data were carried out to propose a new empirical quantitative correlation between soil resistivity and geotechnical characteristics. The improved empirical relationships reflect a very good correlation and it were found that the electrical resistivity of soil has a significant assessment and good fitting with the some of important geotechnical parameters. It was also concluded that the electrical resistivity method which has an advantage over other soil investigation methods that saving and reduce cost. Finally, the new generated empirical equation can be used to evaluate the ultimate bearing capacity of the soil rather than using the traditional widely used equations which require several inputs coefficients calculated using the extensive laboratory and field works. However, the results showed a good and more reliable correlation between soil electrical resistivity and some geotechnical characteristics for the studied region soil.

Gate-tunable high tunneling magnetoresistance induced by hybrid interface states in Ni-electrode single-molecule junctions

Based on the density functional theory and non-equilibrium Green's function method, the modulation effects of gate voltage on the spin transport properties of Ni/triphenylene/Ni single-molecule junctions are investigated. The plane-, platform-, and tip-shaped electrode configurations are considered in the calculations. The numerical results show that the electrode configuration and gate voltage significantly influence the hybrid interface states (HIS) and further the spin transport properties of the molecular junctions. The molecular junctions with plane- and platform-shaped electrode configurations show weak spin polarization (SP) and tunneling magnetoresistance (TMR). Still, they exhibit excellent field effect transistor behaviors with the modulation of the gate voltage. Due to the delocalized spin-down HIS located at the Fermi level, the molecular junction with tip-shaped electrode configuration presents high and controllable SP and TMR behaviors through the gate voltage modulation. The calculations demonstrate that high spin-polarized HIS located at the Fermi level are extremely significant for the generation of excellent spin transport properties in molecular junctions composed of non-magnetic molecule and magnetic electrodes.

(Invited) Reduction of Contact Resistance through the Application of Cylindrical Contacts to WSe2

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are gaining attention as the next-generation semiconductor materials instead of silicon, owing to their atomic thickness and thickness-dependent energy bandgap. Moreover, because of their atomic thickness, TMDs show effective electrostatic gate modulation, thereby short channel effects can be suppressed. Among various TMDs, tungsten diselenide(WSe2) has an ambipolar conductivity which can be tuned to n- or p-type via various processing and shows excellent electrical properties and mechanical stability. However, achieving Ohmic contact in 2D material-metal junction is challenging due to high Schottky barrier and Fermi-level pinning. Therefore, research on the improvement of contact resistance is crucial to maximizing the full potential of 2D materials and utilizing their superior electrical properties. Edge contact, where the junction is formed on the edge of the 2D material layers, has been researched as an effective method to minimize the contact resistance in 2D materials. Unlike the traditional surface contact method, which results in high tunnel barrier and out-of-plane current flow, the edge contact method provides strong orbital overlap and allows in-plane current flow through a narrower tunnel barrier, offering advantages in terms of carrier transport at the contact interface [1]. Yang et al. demonstrated conventional edge contacts to MoS2 using hexagonal boron nitride (h-BN) to encapsulate the surface of the MoS2. This method ensures that current flows only between the edge of the MoS2 and metal [2]. However, this approach necessitates additional process that requires h-BN to completely cover the entire upper part of the contact area and cannot control the area of the edge contact.In this work, edge contact using cylindrical contacts of WSe2 transistors is demonstrated. WSe2 flakes were fabricated through mechanical exfoliation and were dry-transferred on Si/SiO2 substrates. Spin-coating of electron-beam resist and electron-beam lithography (EBL) was performed to prepare the etch mask for cylindrical etching at the contact areas of WSe2. Reactive ion etching was conducted using 15 sccm of Ar, 15 sccm of SF6 with 20 W for 20 s. Spin-coating and EBL process was performed again to define the area for ultraviolet (UV)-ozone treatment and deposition of Pt/Au electrodes. UV-ozone treatment oxidizes the top few layers of WSe2 into WOx, resulting in the p-doping of the underlying WSe2 layer of the contact area. Pt/Au contact metal was deposited by electron-beam evaporation.The fabricated WSe2 FETs shows p-type dominant characteristic and Ohmic behavior, as shown in Fig. 1. Cylindrical contact and UV-ozone treatment process for WSe2 FETs enabled low contact resistance (4 kΩ·μm), high field-effect mobility (149 cm2/V·s) and high on-off ratio (>107). As the perimeter of the cross-sectional circle of the etched cylinder increases, the area of the edge contact becomes larger. The WSe2 FETs with cylindrical contacts exhibited decrease in the contact resistance and increase in the field-effect mobility as the ratio of the etched perimeter to the top contact area increased (Table 1). P-type WSe2 FETs with low contact resistance and high field-effect mobility were demonstrated using cylindrical contacts. With this fabrication, edge contact area can be controlled with the variation of the etched perimeter and electron transport can be improved using both top contact and edge contact.Reference:[1] J. Kang, W. Liu, D. Sarkar, D. Jena, K. Banerjee, Phys. Rev. X 2014,4, 1.[2] Z. Yang, C. Kim, K. Y. Lee, M. Lee, S. Appalakondaiah, C.-H. Ra, K.Watanabe, T. Taniguchi, K. Cho, E. Hwang, J. Hone, W. J. Yoo,Adv.Mater.2019,31, 1808231 Figure 1

Quality Attributes of Four Kale Cultivars Grown in a High Tunnel Ecological Farming System

Quality Attributes of Four Kale Cultivars Grown in a High Tunnel Ecological Farming System

Research on prediction of surrounding rock deformation and optimization of construction parameters of high ground stress tunnel based on WOA-LSTM

To accurately understand the deformation behavior of surrounding rock in the jiugongshan No.2 high ground stress tunnel and optimize construction parameters for improved efficiency, on-site monitoring was used to gather data on rock deformation and initial support contact pressure. A WOA-LSTM regression prediction model was proposed, and excavation advance depth was optimized using numerical simulation. The WOA-LSTM regression prediction model demonstrated high accuracy in tunnel deformation monitoring. The absolute errors between predicted and actual values of tunnel settlement and convergence at various measurement points average 2.53− 04 mm and 1.96− 04 mm, with relative errors averaging 2.15% and 2.34%. These results meet the requirements for guiding construction. Additionally, based on the results of numerical simulation calculations, when the step length is 12 m during the construction of high-stress tunnels using the benching method, excavation advances of 2 m and 3 m result in settlement and convergence increases of 35.1% and 63.4%, and 25.5% and 55.2%, respectively, compared to an excavation advance of 1 m. However, no sudden jumps in these values were observed, indicating that with a 3 m excavation advance, the integrity of the surrounding rock remains in good condition, effectively guiding safe and rapid construction methods.

High-κ monocrystalline dielectrics for low-power two-dimensional electronics.

The downscaling of complementary metal-oxide-semiconductor technology has produced breakthroughs in electronics, but more extreme scaling has hit a wall of device performance degradation. One key challenge is the development of insulators with high dielectric constant, wide bandgap and high tunnel masses. Here, we show that two-dimensional monocrystalline gadolinium pentoxide, which is devised through combining particle swarm optimization algorithm and theoretical calculations and synthesized via van der Waals epitaxy, could exhibit a high dielectric constant of ~25.5 and a wide bandgap simultaneously. A desirable equivalent oxide thickness down to 1 nm with an ultralow leakage current of ~10-4 A cm-2 even at 5 MV cm-1 is achieved. The molybdenum disulfide transistors gated by gadolinium pentoxide exhibit high on/off ratios over 108 and near-Boltzmann-limit subthreshold swing at an operation voltage of 0.5 V. We also constructed inverter circuits with high gain and nanowatt power consumption. This reliable approach to integrating ultrathin monocrystalline insulators paves the way to future nanoelectronics.

Optimizing anaerobic soil disinfestation for high tunnel specialty crop production systems in the U.S. Mid-Atlantic region

Optimizing anaerobic soil disinfestation for high tunnel specialty crop production systems in the U.S. Mid-Atlantic region

Multigenerational Rearing on Non-Prey Foods Does Not Affect Prey (Aphid) Recognition Behavior of Coleomegilla maculata (Coleoptera: Coccinellidae).

The pink spotted lady beetle Coleomegilla maculata has been identified as a promising predator to mass rear and release into greenhouses and high tunnels to control aphids on small fruits and vegetables. This study tested the hypothesis that laboratory-reared C. maculata, without any exposure to aphids for multiple generations, could recognize, attack, and consume live aphids. The aphid adults of two species were collected from non-crop host plants (weeds) over two consecutive seasons. The time (seconds) that C. maculata adults required to recognize and partially or completely consume live, healthy adult aphids was recorded in Petri dish arenas in the laboratory. Regardless of the non-prey food source (brine shrimp egg diet, mealworm-protein-based artificial diet), C. maculata adults readily recognized aphids. Adult females were occasionally more voracious than males. One aphid species (Uroleucon erigeronense) was consumed more readily than the other aphid species (Aphis nerii). In conclusion, multigenerational rearing on non-prey foods did not affect the prey recognition behavior of C. maculata adults in the laboratory. Validating the ability of lady beetles reared on artificial diets to recognize and consume live aphids is an important protocol before augmentative releases for aphid control in greenhouses and high tunnels.

Effects of High Tunnel Soil Solarization on Sclerotinia sclerotiorum in the Temperate Climate of Central Kentucky.

Diseases caused by Sclerotinia spp. can affect a wide range of plants, including vegetables, with yield losses ranging from 10 to 50%. Sclerotinia diseases can be especially problematic in high tunnels where high-value vegetable crops are planted in early spring to extend the growing season, achieve earlier harvest, and bring higher profits. Fungicide applications and crop rotations are limited due to product application restrictions and constraints on time, crop resistance, and profitability. Soil solarization is a cultural management method that uses transparent polyethylene to raise soil temperatures via solar irradiation to kill pathogens, pests, and weeds. A two-year study was conducted in a Kentucky high tunnel to determine the maximum temperature potential of solarization at various soil depths at different durations during different seasons and to identify temperatures at which S. sclerotiorum sclerotia lose viability. The experiment included solarization treatments of 2, 4, and 6 weeks and a non-solarized control implemented in spring, summer, and fall. Sclerotia and temperature data loggers were buried at 5.1, 10.2, and 15.2 cm soil depths. The number of hours at which soil temperatures reached ≥ 40 °C was greatest in summer in both years, followed by fall, and then spring. The highest average daily maximum soil temperature reached was 48.9°C, which occurred during the summer 6-week solarization in Year 1. The viability of buried sclerotia was overall lower in solarized treatments compared to non-solarized treatments in both years. In general, the 2-week solarization treatment had significantly higher percent sclerotial germination than the 4-week and 6-week treatments, which were not significantly different from one another. The viability of sclerotia was progressively higher with burial depth. In both years, sclerotia germination was significantly lower in summer compared to spring and fall.

Durability of a Metakaolin-Incorporated Cement-Based Grouting Material in High Geothermal Tunnels.

To improve the durability of cement-based grout in high geothermal tunnel grouting projects, metakaolin was incorporated to replace 8% of the cement. The permeability, chloride penetration, and sulfate and carbonate erosion tests were carried out on the grout cured at varying temperatures (20, 30, 40, 50, and 60 °C). It was shown that with the increase in curing temperature, the impermeability and resistance to chloride penetration initially increased and then decreased, reaching the highest values at 40 °C. Furthermore, the incorporation of metakaolin into grout enhanced the impermeability by 11.11-38.91% and resistance to chloride penetration by 12.23-12.77%. As attacked by sulfate, the surface spalling of the specimen was more obvious with the increase in the curing temperature and immersion time. Conversely, the appearance remained almost unchanged under carbonate erosion. As immersion time increased, both the antisulfate and anticarbonate erosion coefficients declined. The effect of curing temperature on erosion resistance was assessed via the relative antierosion coefficient. When immersed in sulfate, the coefficient achieved the highest value of 1.08 as cured at 30 °C, and in carbonate, the coefficient reached a maximum of 0.99 as cured at 40 °C. Through scanning electron microscopy and binarized images, it was verified that gypsum and ettringite were formed during sulfate attack, leading to volume expansion and cracking, consequently reducing the strength. Meanwhile, in the case of carbonate erosion, calcium hydroxide (CH) and calcium silicate hydrate gel (C-S-H) were dissolved and degraded, resulting in a large number and size of pores in the grout. The research results have certain theoretical significances and reference values for the application of cement-based grouting materials in high geothermal environments.

Impact of Irrigation Source on the Dissemination and Persistence of Coliforms and Foodborne Pathogens in Fresh Tomato High Tunnel-dripline System from Small Specialty Crop Farms

This study investigated the impact of irrigation sources (pond, stream, and well) in high tunnel-dripline systems on the dissemination and persistence of foodborne pathogens (Escherichia coli O157, Listeria monocytogenes, Campylobacter spp., Salmonella spp., and the ‘big six’ Shiga toxin-producing E. coli [STEC]) in small specialty crop farms (SSCFs). Ten SSCF-growing fresh tomatoes using high tunnel-dripline systems were sampled between January and November 2022. Selective enrichment combined with PCR was used to detect the selected foodborne pathogens in the irrigation water (n = 240), soil (n = 240), and tomato fruits (n = 120). Overall, surface-originated water sources (streams and ponds) having potential contact with farm animals or wildlife harbored higher pathogen burden (cumulative prevalence of all the pathogens) compared to subsurface water source (well and underground spring water). STEC O26, O45, and O103 were detected at high frequency (up to 88% per SSCF per time point) in the water source and associated dripline irrigation system of 4/6 SSCFs using stream and pond water. Other foodborne pathogens (especially, L. monocytogenes) were detected in 6/10 SSCFs, but at low frequency (<25% per SSCF per time point). The prevalence of foodborne pathogens in the 10 SSCFs over time was positively correlated with the length of high tunnel and planting date (r2 = 0.93 and 0.79, respectively; P < 0.006). Our study highlighted that dripline irrigation systems may allow the long-distance transport of foodborne pathogens from the contaminated water source to the field. Risk assessment and mitigation measures should be implemented to assure the quality of the water source used for irrigation in SSCF.

Hydro-mechanical modeling of cohesive crack propagation of concrete lining in high internal pressure tunnels

High pressure tunnels with concrete lining have been extensively utilized in project practice. However, due to the characteristic of concrete being susceptible to cracking under tension, the lining inevitably develops cracks under high internal water pressure, posing a serious threat to the operation of tunnels. This study aims at developing a hydro-mechanical numerical model of cohesive crack propagation of concrete lining in high internal pressure tunnels. In this regard, the determination of cohesive element parameters is elucidated, the contact simulation within the software ABAQUS is improved to accurately characterize the interface between lining and surrounding rock, and the numerical calculation process in ABAQUS is realized using indirect coupled method. The simulation results align well with the physical model test and engineering monitoring data, demonstrating that the proposed method can accurately simulate the hydraulic interactions of high pressure tunnel. Additionally, a comparison with calculation models employing tie constraints to simulate the lining-surrounding rock interface is conducted. Finally, comparison with traditional continuum method reveals that while both methods exhibit consistent overall trends. It is recommended to choose the proposed method when describing the discontinuous propagation process of cracks, which cannot be simulated by the continuum analysis method.