247 research outputs found

    Development of an online food safety training and pilot study for employees of university farms and school gardens

    Get PDF
    Two one-hour on farm food safety online module were developed to inform k-12 students and university farm workers on food safety hazards associated with production and harvesting of fresh produce. Module content was developed through a review of the current Good Agricultural Practices (GAPs) Program, current research available, and updated regulations in produce food safety. Quizzes for students and a user manual were created for facilitators and instructors to support the online modules. After developing the course materials, a pilot study was conducted at two k-12 school districts in Iowa, two land grant universities, with a six member expert steering committee panel to test the knowledge gained through the two developed curriculum. The six member expert steering committee along with three other facilitators completed an online survey consisting of open-ended questions to determine the effectiveness of the online module and the supporting materials available on the inclusive webpage. The hypothesis of this research is that the online curriculum and supportive material will be beneficial to both demographics, and increase in knowledge will be observed after viewing developed material. Students and university survey results indicate that the online module will significantly increase the knowledge of students and university workers related to hazards associated with produce food safety (P\u3c0.05). The topics, graphics, design, length, and webpage were appropriate for the age group. Additionally, the resource guide and quizzes were perceived as helpful and will be useful to increase the knowledge and confidence of the training facilitators (P\u3c0.05). The group indicated that specific graphic and content material changes should be made within the module. This online module is a first step toward educating youth about food safety in the garden. Knowledge on hazard prevention can reduce the risk of produce contamination and decrease produce outbreaks from occurring in school gardens

    WordCruncher: A Digital Research and Teaching Assistant

    Get PDF
    For humanities research or teaching projects, we each pick tools from our digital toolboxes. If we have few tools, our projects may be limited or take longer. When we become familiar with other tools, we may get ideas for other projects and learn how to do projects faster and better. WordCruncher is a free digital toolkit with tools to help you search, study, analyze, download, create, and share eBooks or corpora. For example, you can add searchable notes, highlight text, do advanced searches, see search keywords in context, and find collocates or n-grams in WordCruncher books that may include formatted multilingual text, images, tags, hyperlinks, dictionaries, and lemma lists. Other apps and online resources may lack helpful tools, tags, markup, formatting, speed, or data. One linguist used online data to create a 700 million-word WordCruncher corpus. He said, “I couldn\u27t have done a lot of my research with what is out there.” For many years, our team has helped BYU faculty, research assistants, and students use WordCruncher tools to answer research questions and enhance student learning. We often help convert digital materials into a WordCruncher book or corpus designed to facilitate a project. This presentation will be a quick overview of several projects that illustrate how faculty and students have used WordCrunchertools and data

    Quantitative estimation of localization errors of 3 d transition metal pseudopotentials in diffusion Monte Carlo

    Get PDF
    The necessarily approximate evaluation of non-local pseudopotentials in diffusion Monte Carlo (DMC) introduces localization errors. We estimate these errors for two families of non-local pseudopotentials for the first-row transition metal atoms Sc-Zn using an extrapolation scheme and multideterminant wavefunctions. Sensitivities of the error in the DMC energies to the Jastrow factor are used to estimate the quality of two sets of pseudopotentials with respect to locality error reduction. The locality approximation and T-moves scheme are also compared for accuracy of total energies. After estimating the removal of the locality and T-moves errors, we present the range of fixed-node energies between a single determinant description and a full valence multideterminant complete active space expansion. The results for these pseudopotentials agree with previous findings that the locality approximation is less sensitive to changes in the Jastrow than T-moves yielding more accurate total energies, however not necessarily more accurate energy differences. For both the locality approximation and T-moves, we find decreasing Jastrow sensitivity moving left to right across the series Sc-Zn. The recently generated pseudopotentials of Krogel et al. [Phys. Rev. B 93, 075143 (2016)] reduce the magnitude of the locality error compared with the pseudopotentials of Burkatzki et al. [J. Chem. Phys. 129, 164115 (2008)] by an average estimated 40% using the locality approximation. The estimated locality error is equivalent for both sets of pseudopotentials when T-moves is used. For the Sc-Zn atomic series with these pseudopotentials, and using up to three-body Jastrow factors, our results suggest that the fixed-node error is dominant over the locality error when a single determinant is used

    Computational Modeling of Gas Adsorption, Separation, and Reactivity within Coordinatively Unsaturated Metal-Organic Framework Materials

    Get PDF
    University of Minnesota Ph.D. dissertation.March 2015. Major: Chemistry. Advisor: Laura Gagliardi. 1 computer file (PDF); xix, 238 pages.In this work, computational methodologies are used to investigate the behavior of Metal-Organic Frameworks (MOFs) that are of potential utility in gas separation ap- plications. MOFs are three-dimensional porous materials that are desirable due to their high porosity and internal surface area. Given the myriad of possible framework topologies, computational tools are necessary in order to aid and complement experimental efforts. The focus of this dissertation is specifically coordinatively unsaturated MOFs, a subclass of MOFs for which there are additional computational challenges in treating the exposed metal site. The collection of studies presented here are grouped into four categories: force field parameterization, gas reactivity within MOFs, nature of adsorbate-MOF bonding, and multireference treatment of metal-metal bonds. Ab initio force fields are parameterized for various MOF-gas interactions, where the the NonEmpirical Modeling (NEMO) philosophy is adopted. Wave-Function Theory (WFT) is used for the calculation of the reference energies of the intermolecular terms. Moller-Plesset Perturbation Theory to 2nd order (MP2) and Complete-Active Space Perturbation Theory to 2nd order (CASPT2) are applied for closed-shell and open-shell cases, respectively. These derived force fields are utilized in Grand Canonical Monte Carlo (GCMC) simulations for the MOF + adsorbate systems. Results from GCMC simulations include adsorption isotherms, Henry coefficients, and isosteric heats of adsorption that are compared with the available experimental data, demonstrating the predictive capabilities of this computational procedure. A reaction mechanism between CO2 and amines grafted within the pores of a MOF is proposed based on DFT results, and both DFT and CASPT2 results are utilized to elucidate the nature of a reactive Fe-Oxo intermediate at the exposed Fe site in the MOF. Coupled Cluster (CC), MP2, CASPT2, and DFT are all used to rationalize adsorbate-MOF bonding trends, and the Extended-Transition State Natural Orbitals for Chemical Valence (ETS-NOCV) is used as a comparative tool. Complete-Active Space Self-Consistent Field (CASSCF) and CASPT2 are used for the studies of metal-metal multiple bonded species, and compared with results from DFT

    Improving Agricultural Workers Food Safety Knowledge through an Online Curriculum

    Get PDF
    Abstract A one-hour online food safety curriculum was developed to inform university farm workers on food safety hazards associated with production and harvesting of fresh produce. The farm curriculum consists of five sections (food safety importance, pre-harvest hazards, post-harvest hazards, personal hygiene, and regulations). Engagement activities and a user manual were developed to support the curriculum. Curriculum content was validated by an expert panel and a convenience panel of farm workers. The developed curriculum was piloted at two land grant universities (n=50). Multiple-choice quizzes were used to assess knowledge changes in each of the sections. Results indicated significant knowledge gains at both universities for all sections except the personal hygiene section. This pilot study provides evidence that an online format is effective in improving food safety knowledge. Because knowledge is a prerequisite for behavior, this curriculum can assist with mitigating food safety risk on university and other research farms. Keywords: Food Safety Education, University Farms, Pilot Study, Online Trainin

    Correction: CO2 induced phase transitions in diamine-appended metal-organic frameworks (Chemical Science (2015) 6 (5177-5185) DOI: 10.1039/c5sc01828e)

    Get PDF
    The authors regret that there are some discrepancies reproducing the data in the original article due to the determined coordinates not being the fully optimised geometries. The authors have provided more information as follows. In the manuscript entitled \u27CO2 induced phase transitions in diamine-appended metal-organic frameworks\u27, minor errors with the attached coordinates and energies reported in the paper have recently been identified. In this communication, we correct these errors. Here, we present updated optimized geometries and binding energies. We also take this opportunity to include an extended computational details section to ensure reproducibility. In addition, we show that the overall conclusions of the paper are not affected by these changes. A detailed comparison with the results reported by Lee et al.1 revealed that the DFT optimization of the coordinates provided with the manuscript do not lead to the values reported in the manuscript, and they warrant correction. Corrected coordinates and updated tables (Tables 1-7) and figures (Fig. 1, 2, 4 and 5) are included here for calculations using the PBE functional. These structures have been repeated using a slightly tighter force threshold than in the original manuscript (details below). The M06-L calculations reported in the original manuscript are not revisited since they were performed to assess the role of dispersion. Since the publication of our work in 2015, a far more detailed study of this effect has been published by one of the authors rendering these M06-L calculations unnecessary and we refer readers interested in the role of dispersion on the carbamate formation to this more recent study by Lee et al.1 In addition to correcting our DFT calculations, we examine the effects of the revised DFT values on the lattice model in this work.We recompute the lattice model with the M06-L and PBE values fromthe original manuscript as well as the corrected PBE values reported below (Fig. 6-8 and Tables 8-10). In all three sets of isotherm plots the ordering is preserved but the inflection points are spaced differently with the new PBE numbers, leading to quantitative differences that are nonetheless qualitatively similar to previous work. Finally, we discuss different ways that CO2 can coordinate to the metal binding site, as shown in Fig. 3. We should have notedmore clearly in ourmanuscript that these were starting configurations and not necessarily the final converged structures since our goal was to try several starting geometries to determine which coordination environment around the metal site was lowest in energy. Take for example bidentate insertion. Chemical intuition suggests that this structure could rotate to one that has only one CO2 oxygen center closer to the metal than the other and we observe this in our optimized structure. The resulting geometries we obtained for the starting arrangements noted in the figure are higher in energy than the chain model as reported in our original paper.We wish to emphasize that at the time of our 2015 study, our objective was to understand whether or not CO2 was bound to the metal and if one-dimensional chain formation could lead to a step in the adsorption isotherm. It has since become clear that a far more thorough study of the arrangements of the amines is required to truly understand competing amine arrangements preset in experiment. This was outside the scope of our work. Once more, these calculations are perhaps now outdated given work in the field in recent years. We again refer interested readers to a more recent study by Lee et al.1 1. Extended computational details to ensure reproducibility In the course of rectifying the error in our calculations, we wanted to ensure that all revised calculations were converged using the exact same protocol; therefore, we repeated the PBE calculations for the pair and chain models using updated computational details given here to ensure reproducibility. The M2(dobpdc) MOF contains six unsaturated metal sites per unit cell. To calculate the binding energies of CO2 in its amine appended analogue mmen-M2(dobpdc), one mmen ligand per CO2 was added per unit cell. The smaller sized ethylenediamine (en) was used to saturate the remaining amines not involved in CO2 binding. In the case of the pair mode, two mmen-amines are included per unit cell only. All DFT calculations were performed with periodic boundary conditions carried out using the VASP 5.4.4 package (original calculations were performed with VASP 5.3.3). The PBE functional was employed to examine the energetics of CO2 adsorption.3 On-site Hubbard U corrections were employed for metal d electrons.4 The U values are determined to reproduce oxidation energies in the respective metal oxides and are given in the tables below. The electron-ion interactions in these calculations were described with the projector augmented wave (PAW) method developed by Blöchl with an energy cutoff of 550 eV.5 This combination of the PBE functional, PAW scheme, and energy cutoff was used for full geometry optimization of the various species investigated until the forces on all atoms were smaller than 0.02 eV Å-1 and the SCF convergence was set to 1 × 10-7 eV. Given the large size of the unit cell and the tests with other numbers of K-points from the original study, only results obtained from G-point calculations are reported here. Finally, heats of adsorption are now reported below along with E + ZPE values, while in the original manuscript only E + ZPE were reported. No changes were made to how the vibrational corrections were computed; however, we have included some additional details to ensure reproducibility.6 Harmonic vibrational modes (ωi) were computed for CO2 in the gas phase and its bound product state (amine-CO2-MOF complex). The framework itself was taken to be rigid and only the vibrational modes associated with the motion of the amine, the metal center, first coordination sphere (oxygen atoms bound to the metal in the MOF backbone), and (if present) the bound CO2 were computed. Since the harmonic approximation breaks down for low frequency modes, we replaced all modes less than 50 cm-1 with 50 cm-1 when computing the zero-point and thermal energies. The following standard harmonic expressions were used to compute the vibrational corrections: Zero-point vibrational energy (ZPE) is: [Equation presented here] While for the bound product, the rotational and translational degrees of freedom of CO2 have been converted to additional vibrational modes allowing one to compute the thermal correction simply as: [Equation presented here] 2. Values for the chain model The chain model used in our original study included 1 mmen- and 5 en-amines. The values from the original paper are reported in Table 1. When we repeat these calculations using the procedure described in Section 1, we obtain the values in Table 2. In addition to the chain model described above (1 mmen- and 5 en-amines per unit cell), during our original study we performed calculations with another model that was not included in the manuscript since its values yielded results further from experiment. This model includes only 1 mmen-amine per unit cell (no other amines) and was used to test the assumption that the five enamines are indeed spectators with respect to the metal dependence of the binding energy. We present the results from this model in Table 3. In the original paper we noted that the energy and bond length trends are correlated and are consistent with the Irving-Williams series. This is no longer true for all metals under investigation, with Zn being an outlier. The results for Zn can be explained by more recent work.1 3. Values for the pair model The model used to compute the pair adsorption mechanisms included 2 mmen-amines and 0 en-amines. The values in the original paper are presented in Table 5. 4. Lattice model plots The lattice models to generate adsorption isotherms for these systems were run at one temperature (∼25 °C) using four different input parameters. First the M06-L and PBE values from the original paper were used once more as it has been some time since we have run the lattice model. Then the model is repeated with the new set of values from PBE. If we compare Fig. 7 and 8, the order is preserved, but the infliction points are spaced a bit differently. This is due to the scaling factor being constant and is something we scaled for each of the different systems as well. The slope is also a bit different, but not more then we should expect for this simple lattice model. Furthermore, we only ever aimed to reproduce the step and the order of the metals. Any finer details cannot be expected to be obtained from this model. The exact values used to compute the isotherms are given in the tables below. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers

    MnNiO3 revisited with modern theoretical and experimental methods

    Get PDF
    MnNiO3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photocatalyst. However, there is no experimental report on critical quantities such as the band gap or bulk modulus. Recent theoretical predictions with standard functionals such as LDA+U and HSE show large discrepancies in the band gaps (about 1.23 eV), depending on the nature of the functional used. Hence there is clearly a need for an accurate quantitative prediction of the band gap to gauge its utility as a photocatalyst. In this work, we present a diffusion quantum Monte Carlo study of the bulk properties of MnNiO3 and revisit the synthesis and experimental properties of the compound. We predict quasiparticle band gaps of 2.0(5) eV and 3.8(6) eV for the majority and minority spin channels, respectively, and an equilibrium volume of 92.8 Å3, which compares well to the experimental value of 94.4 Å3. A bulk modulus of 217 GPa is predicted for MnNiO3. We rationalize the difficulty for the formation of ordered ilmenite-type structure with specific sites for Ni and Mn to be potentially due to the formation of antisite defects that form during synthesis, which ultimately affects the physical properties of MnNiO3

    3β-Hy­droxy­lup-20(29)-en-28-yl 1H-imidazole-1-carboxyl­ate

    Get PDF
    The title triterpene, C34H52N2O3, is a C-28 carbamate derivative of betulin prepared in a one-step reaction from the commercially available 1,1′-carbonyl­diimidazole (CDI). All rings are fused trans. The X-ray study shows the retention of the configuration of C-28 with respect to the known chiral centres of the molecule. In the crystal, the mol­ecules are O—H⋯O hydrogen bonded via the hy­droxy group and the carbonyl group of the carbamate function into chains running along the c axis. A quantum-mechanical ab initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated mol­ecule gives values for bond-lengths and valency angles close to the experimental values. The calculations also reproduce the mol­ecular conformation well, with calculated puckering parameters that agree well with the observed values
    corecore