Guest transport in a nonporous organic solid via dynamic van der Waals cooperativity

A well-known organic host compound undergoes single-crystal-to-single-crystal phase transitions upon guest uptake and release. Despite a lack of porosity of the material, guest transport through the solid occurs readily until a thermodynamically stable structure is achieved. In order to actively facilitate this dynamic process, the host molecules undergo significant positional and/or orientational rearrangement. This transformation of the host lattice is triggered by weak van der Waals interactions between the molecular components. In order for the material to maintain its macroscopic integrity, extensive cooperativity must exist between the molecules throughout the crystal, such that rearrangement can occur in a well-orchestrated fashion. We demonstrate here that even weak dispersive forces can exert a profound influence over solid-state dynamics.     

Fieldwork in a Cold Climate

It is essential that proper advanced preparation is in place before initiating a field project situated in a cold environment. Protection of the body from the wind, precipitation, and low temperatures through the use of appropriate clothing is a key to survival. Having appropriate cold-climate clothing is important, but also wearing this clothing in a manner that is most effective at maintaining a normal body temperature will help prevent both hypothermia and hyperthermia. Proper preparation includes working emergency equipment, knowledge of how to use the emergency equipment, and developing a field plan to leave with a contact. Special care must be provided to medications in a freezing environment, and there are methods that ensure that treatments can occur when needed.     

Effect of Albizia julibrissin water extracts on low-density lipoprotein oxidization

High-value phytochemicals could be extracted from biomass prior to the current cellulosic pretreatment technologies (i.e., lime, ammonia, dilute acid, or pressurized hot water treatments) provided that the extraction is performed with a solvent that is compatible with the pretreatment. This work reports on the extraction of flavonoids from Albizia julibrissin biomass. While extracting A. julibrissin foliage with 50 degrees C water, 2.227 mg/g of hyperoside and 8.134 mg/g quercitrin were obtained, which is in the realm of what was obtained with 60% methanol. A. julibrissin foliage, flower, and whole plant extracts were tested in terms of their potential to inhibit low-density lipoprotein (LDL) oxidization. The highest inhibition was obtained with foliage water extracts, which were standardized at 2.5 microM of flavonoids. Also, the 2.5 microM foliage water extract resulted in a reduction from 43% to only 1% of the observed monocyte adherence. To have commercial application, A. julibrissin water extracts should be devoid of toxicity. The A. julibrissin foliage, flower, and whole plant water extracts were not toxic to Vero 76 cells. In summary, A. julibrissin biomass can be extracted with 50 degrees C water to yield an antioxidant stream, showing that it may be possible to couple extraction of valuable phytochemicals to the cellulosic pretreatment step.     

Scale‐dependent effects of isolation on seasonal patch colonisation by two Neotropical freshwater fishes

The metapopulation paradigm has been central to improve the conservation and management of natural populations. However, despite the large number of studies on metapopulation dynamics, the overall support for the relationships on which the paradigm is based has not been strong. Here, we studied the occupancy dynamics of two Neotropical fishes (i.e., Pimelodella gracilis and Leporinus friderici) to investigate two fundamental premises of the metapopulation paradigm, that is, that isolation and area/habitat quality affect colonisation and extinction probabilities in predictable ways. In order to do this, we used a modification of occupancy models that allows modelling the probability of a site's occupancy as a function of the occupancy of its neighbourhood. We found a weak positive effect of neighbourhood occupancy on P. gracilis colonisation, which is consistent with the propagule rain metapopulation, that is, colonists arriving from outside the studied system. However, we found a strong negative neighbourhood effect on extinction probability, suggesting that declining populations from stream sections are rescued from extinction by neighbouring patches. In contrast, the effect of neighbourhood occupancy on the metapopulation dynamics of L. friderici was in the opposite direction, affecting positively colonisation but not affecting extinction rates, which is consistent with the classical metapopulation model. In addition, the occupancy dynamics of both species were affected by water velocity. To our knowledge, this is the first study to link directly dispersal to local population dynamics in Neotropical fishes, and one of the few studies doing inferences on spatial population dynamics based on direct estimates of neighbourhood occupancy.     

Variability of light interception and radiation use efficiency in maize and soybean

Variability of light interception and its derivatives are poorly understood at the field-scale in maize (Zea mays L.) and soybean [Glyine max (L.) Merr.]. Quantifying variability can provide reliable estimates of field-scale processes and reliable methodology. A field study was conducted during the 2005 growing season in a 31 ha maize and 23 ha soybean field rotated annually near Ames, IA to measure variability of cumulatively intercepted photosynthetically active radiation (CI-PAR) and radiation use efficiency (RUE) by deploying eight line quantum sensors in each field. Cumulative mean PAR interception for soybean was 575 MJ m⁻² ending on day of the year (DOY) 249 compared with 687 MJ m⁻² in maize ending on DOY 244. Soybean standard error (s_X) for a single sensor was 4.48% and with six sensors was 1.83% of the final CI-PAR. Maize s_X for a single sensor was 5.29% and with eight sensors was 1.87% of the final CI-PAR. Crop biomass was quantified weekly by collecting four 1 m² samples. Soybean RUE using all sensors was 1.44 ± 0.06 g MJ PAR⁻¹. The highest CI-PAR from a single sensor had RUE of 1.32 and the lowest was 1.55 g MJ PAR⁻¹. Maize RUE using all sensors was 3.35 ± 0.09. The highest CI-PAR from a single sensor had RUE of 2.87 and the lowest was 3.70 g MJ PAR⁻¹. Reliable transmitted PAR and RUE estimates are obtainable at the field-scale in maize and soybean with four and three sensors, respectively, assuming that crop biomass is accurately measured.     

Multi-Year Measurements of Field-Scale Metolachlor Volatilization

Volatilization is a critical pathway for herbicide loss from agricultural fields, and subsequently deposited downwind from the edge of the field. To better understand the volatilization process, field-scale turbulent volatilization fluxes of metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide) were quantified for 13 consecutive years using a combination of herbicide concentration profiles and eddy diffusivities derived from turbulent fluxes of heat and water vapor. Site location, type of herbicides, and agricultural management practices remained unchanged during this study in order to evaluate the effect of soil moisture on metolachlor volatilization. Twenty gravimetric surface soil moisture samples (0–5 cm) were collected immediately after herbicide application and then at 0430 hours each morning to determine the impact of surface moisture on herbicide volatilization. Five days after application, cumulative herbicide volatilization ranged from 5 to 63% of that applied for metolachlor. Metolachlor volatilization remained an important loss process more than 5 days after application when the soil surface was moist. Conversely, if the soil surface was dry, negligible volatilization occurred beyond 5 days. Furthermore, the total amount of metolachlor volatilized into the atmosphere increased exponentially with surface soil water content during application (r ²?=?0.78). Metolachlor volatility was found to be governed largely by surface soil moisture.     

Response of maize (Zea mays) inbreds and hybrids to rimsulfuron

Abstract: Extensive glasshouse studies characterized the varietal response to rimsulfuron of 37 inbreds of maize (Zea mays L.), representing the major inbred families used in hybrid seed production, and 20 defined hybrids from these inbreds. Tolerant hybrids were produced when one or both of its parents were tolerant. Sensitive hybrids occurred only when both parents were sensitive. Genetic analysis indicated that sensitivity is controlled by a single recessive gene. Dose-response analysis showed varieties could vary more than 40000-fold in sensitivity. Only the AHAS-modified variety with the XA-17 gene had changed enzyme sensitivity. This gene provided crop tolerance to very high rates of rimsulfuron and its interaction with an organophosphate insecticide. Breeders can eliminate varietal sensitivity in three ways: always use at least one tolerant hybrid parent, backcross sensitive inbreds with tolerant, or use an AHAS-modified gene.     

A cross-sectional study of the causes of morbidity and mortality in farmed white-tailed deer

Two questionnaires were designed and administered. The first was to a random sample of 340 farmers of white-tailed deer (Odocoileus virginianus) in Canada and the United States. The second was a 10-year retrospective survey of deer submissions to veterinary diagnostic pathology laboratories in Canada and the United States. One-year rates of mortality and common causes of morbidity and mortality for the deer are reported. The primary diagnosis for each record was used to classify diseases into categories, such as parasitic, infectious, toxicological, and neoplastic. Submissions were further classified according to the anatomical location, the pathological change, and the etiology associated with each lesion. Trauma was the most important reported cause of farmed white-tailed deer mortality; necrobacillosis was a major cause of morbidity and mortality, especially in fawns.