Weed Aggressivity in Agronomic Crops

The quantity of herbicides applied in crops has disturbed environmentalists for many years and several environmental groups have voiced distress about the impact of herbicides on water quality, the food supply, and human health. These concerns are causing administrators, scientists, and farmers to search for farming practices and research programs that can effectively balance agri chemical usage with the protection of national resources, food supplies, and human health (Anonymous, 1989a; Anonymous, 1989b). Society will become more environmentally sensitive, and agricultural practices will become more environmentally friendly. Pesticides that cause unacceptable environmental damage or threaten health will be withdrawn. During the next 20 years many of today\u27s chemical pesticides will become obsolete. Certain environmentally friendly herbicides, like glyphosate, will still be used, often in combination with biotechnology, to replace less friendly herbicides (Schneiderman and Carpenter, 1990). Environmental pressures have led to a growing demand for an overall reduction in the use of pesticides and, in countries such as Denmark, Sweden, and the Netherlands, such a reduction has become formal government policy (Thomas, 1990). New research programs must be initiated that include on-farm studies of farming systems and the development of computer software and systems to aid farmers in the management and decision making needed to adopt alternative systems (Anonymous, 1989b)

Demonstration of a Weed Management Expert System for Crop Production

Abstract. The employment of a computer model to facilitate weed management decisions has the potential to reduce herbicide use when weed densities are below an economical threshold as opposed to applying prophylactic herbicide treatments in anticipation of weed problems. The computer model was constructed by linking two submodels representing soil-applied and postemergence weed management decisions. The models are farm specific, user friendly, and consider most herbicide options and herbicide efficacy by weed species. The submodels were developed in LOTUS

Studies of Some Inorganic Reaction Mechanisms

Part I The compound dihydridotetrakis (diethylphenylphosphonite)-iron(II) is known to undergo rapid rearrangement in solution. Considerable discussion has been presented to formulate a mechanism for this rearrangement. This discussion is based on a rearrangement between cis and trans dihydride isomers of octahedral stereochemistry. We present here some experimental evidence which shows the identification of one isomer (as the trans dihydride) is incorrect and also that the changes that occur are more complicated than the earlier workers proposed. Infrared, Raman, and very low temperature 1H n. m. r. spectra of both the iron and ruthenium compounds are used to construct a different picture of this system. We identify three distinct reactions or rearrangements that are occurring and offer some proposals for the structures of the isomers. A non-classical six-coordinate structure based on a tetrahedral skeleton of phosphorus atoms about the central metal is considered the most reasonable identification of the non-cis isomer. Part II Nitric oxide undergoes many reactions to form transition metal nitrosyls of varying geometry. Under very special conditions, it then continues to react to form a species with nitrogen to nitrogen bonds. We have studied one of these reactions in detail: First, to establish the stoichiometry of the reaction exactly and second, to gain some insight into the mechanism of the dimerization step. There is an initial rapid reaction of an ammoniacal Co(II) solution and NO with the stoichiometry one NO per cobalt(II). The NO pressure dependence of the ratio NO to cobalt is given experimentally. A qualitative proposal is made to explain this dependence, but we are still searching for a quantitative description. There is a much slower reaction that consumes additional nitric oxide, producing N2O and nitrite ions. If the initial cobalt(II) concentration is high, an additional product is obtained, the μ-hyponitrito bis(pentaammine cobalt(III)) ion, usually precipitated as the nitrate. The yield of the dimeric cation as a function of concentration, anion, and temperature are given. A proposal of a linkage isomerization of an unstable dimer of pentaamminenitrosyl cobalt(III) is offered to explain the experimental observations. Part III The decomposition of nitric oxide to elements in the gas phase is a thermodynamically favored reaction that is very slow at low temperatures (below 1000°K). Some catalysts are known for this reaction carried out in a heterogeneous reactor. Work has been performed jointly with the chemical engineering faculty to try to understand the reaction over one of the known catalysts. The rate limiting factor is shown to be the strong inhibition by the product oxygen rather than any intrinsically slow reaction of NO. An interpretation of both our results and the results of another group is offered in terms of a unimolecular decomposition on a surface.</p

Decolonization in Prevention of Health Care-Associated Infections

Colonization with health care-associated pathogens such as Staphylococcus aureus, enterococci, Gram-negative organisms, and Clostridium difficile is associated with increased risk of infection. Decolonization is an evidence-based intervention that can be used to prevent health care-associated infections (HAIs). This review evaluates agents used for nasal topical decolonization, topical (e.g., skin) decolonization, oral decolonization, and selective digestive or oropharyngeal decontamination. Although the majority of studies performed to date have focused on S. aureus decolonization, there is increasing interest in how to apply decolonization strategies to reduce infections due to Gram-negative organisms, especially those that are multidrug resistant. Nasal topical decolonization agents reviewed include mupirocin, bacitracin, retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, photodynamic therapy, omiganan pentahydrochloride, and lysostaphin. Mupirocin is still the gold standard agent for S. aureus nasal decolonization, but there is concern about mupirocin resistance, and alternative agents are needed. Of the other nasal decolonization agents, large clinical trials are still needed to evaluate the effectiveness of retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, omiganan pentahydrochloride, and lysostaphin. Given inferior outcomes and increased risk of allergic dermatitis, the use of bacitracin-containing compounds cannot be recommended as a decolonization strategy. Topical decolonization agents reviewed included chlorhexidine gluconate (CHG), hexachlorophane, povidone-iodine, triclosan, and sodium hypochlorite. Of these, CHG is the skin decolonization agent that has the strongest evidence base, and sodium hypochlorite can also be recommended. CHG is associated with prevention of infections due to Gram-positive and Gram-negative organisms as well as Candida. Conversely, triclosan use is discouraged, and topical decolonization with hexachlorophane and povidone-iodine cannot be recommended at this time. There is also evidence to support use of selective digestive decontamination and selective oropharyngeal decontamination, but additional studies are needed to assess resistance to these agents, especially selection for resistance among Gram-negative organisms. The strongest evidence for decolonization is for use among surgical patients as a strategy to prevent surgical site infections

The Development and Internal Evaluation of a Predictive Model to Identify for Whom Mindfulness-Based Cognitive Therapy Offers Superior Relapse Prevention for Recurrent Depression Versus Maintenance Antidepressant Medication

Depression is highly recurrent, even following successful pharmacological and/or psychological intervention. We aimed to develop clinical prediction models to inform adults with recurrent depression choosing between antidepressant medication (ADM) maintenance or switching to mindfulness-based cognitive therapy (MBCT). Using previously published data ( N = 424), we constructed prognostic models using elastic-net regression that combined demographic, clinical, and psychological factors to predict relapse at 24 months under ADM or MBCT. Only the ADM model (discrimination performance: area under the curve [AUC] = .68) predicted relapse better than baseline depression severity (AUC = .54; one-tailed DeLong’s test: z = 2.8, p = .003). Individuals with the poorest ADM prognoses who switched to MBCT had better outcomes compared with individuals who maintained ADM (48% vs. 70% relapse, respectively; superior survival times, z = −2.7, p = .008). For individuals with moderate to good ADM prognoses, both treatments resulted in similar likelihood of relapse. If replicated, the results suggest that predictive modeling can inform clinical decision-making around relapse prevention in recurrent depression

Estimating the effective elastic modulus and specific fracture energy of snowpack layers from field experiments

Measurements of the mechanical properties of snow are essential for improving our understanding and the prediction of snow failure and hence avalanche release. We performed fracture mechanical experiments in which a crack was initiated by a saw in a weak snow layer underlying cohesive snow slab layers. Using particle tracking velocimetry (PTV), the displacement field of the slab was determined and used to derive the mechanical energy of the system as a function of crack length. By fitting the estimates of mechanical energy to an analytical expression, we determined the slab effective elastic modulus and weak layer specific fracture energy for 80 different snowpack combinations, including persistent and nonpersistent weak snow layers. The effective elastic modulus of the slab ranged from 0.08 to 34 MPa and increased with mean slab density following a power-law relationship. The weak layer specific fracture energy ranged from 0.08 to 2.7 J m−2 and increased with overburden. While the values obtained for the effective elastic modulus of the slab agree with previously published low-frequency laboratory measurements over the entire density range, the values of the weak layer specific fracture energy are in some cases unrealistically high as they exceeded those of ice. We attribute this discrepancy to the fact that our linear elastic approach does not account for energy dissipation due to non-linear parts of the deformation in the slab and/or weak layer, which would undoubtedly decrease the amount of strain energy available for crack propagation

Selenoprotein gene nomenclature

The human genome contains 25 genes coding for selenocysteine-containing proteins (selenoproteins). These proteins are involved in a variety of functions, most notably redox homeostasis. Selenoprotein enzymes with known functions are designated according to these functions: TXNRD1, TXNRD2, and TXNRD3 (thioredoxin reductases), GPX1, GPX2, GPX3, GPX4 and GPX6 (glutathione peroxidases), DIO1, DIO2, and DIO3 (iodothyronine deiodinases), MSRB1 (methionine-R-sulfoxide reductase 1) and SEPHS2 (selenophosphate synthetase 2). Selenoproteins without known functions have traditionally been denoted by SEL or SEP symbols. However, these symbols are sometimes ambiguous and conflict with the approved nomenclature for several other genes. Therefore, there is a need to implement a rational and coherent nomenclature system for selenoprotein-encoding genes. Our solution is to use the root symbol SELENO followed by a letter. This nomenclature applies to SELENOF (selenoprotein F, the 15 kDa selenoprotein, SEP15), SELENOH (selenoprotein H, SELH, C11orf31), SELENOI (selenoprotein I, SELI, EPT1), SELENOK (selenoprotein K, SELK), SELENOM (selenoprotein M, SELM), SELENON (selenoprotein N, SEPN1, SELN), SELENOO (selenoprotein O, SELO), SELENOP (selenoprotein P, SeP, SEPP1, SELP), SELENOS (selenoprotein S, SELS, SEPS1, VIMP), SELENOT (selenoprotein T, SELT), SELENOV (selenoprotein V, SELV) and SELENOW (selenoprotein W, SELW, SEPW1). This system, approved by the HUGO Gene Nomenclature Committee, also resolves conflicting, missing and ambiguous designations for selenoprotein genes and is applicable to selenoproteins across vertebrates

Selenium status is positively associated with bone mineral density in healthy aging European men

Objective It is still a matter of debate if subtle changes in selenium (Se) status affect thyroid function tests (TFTs) and bone mineral density (BMD). This is particularly relevant for the elderly, whose nutritional status is more vulnerable. Design and Methods We investigated Se status in a cohort of 387 healthy elderly men (median age 77 yrs; inter quartile range 75-80 yrs) in relation to TFTs and BMD. Se status was determined by measuring both plasma selenoprotein P (SePP) and Se. Results The overall Se status in our population was low normal with only 0.5% (2/387) of subjects meeting the criteria for Se deficiency. SePP and Se levels were not associated with thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroxine (T4), triiodothyronine (T3) or reverse triiodothyronine (rT3) levels. The T3/T4 and T3/rT3 ratios, reflecting peripheral metabolism of thyroid hormone, were not associated with Se status either. SePP and Se were positively associated with total BMD and femoral trochanter BMD. Se, but not SePP, was positively associated with femoral neck and ward's BMD. Multivariate linear analyses showed that these associations remain statistically significant in a model including TSH, FT4, body mass index, physical performance score, age, smoking, diabetes mellitus and number of medication use. Conclusion Our study demonstrates that Se status, within the normal European marginally supplied range, is positively associated with BMD in healthy aging men, independent of thyroid function. Thyroid function tests appear unaffected by Se status in this population