Effects of Monomer Structure on Their Organization and Polymerization in a Smectic Liquid Crystal

Photopolymerizable diacrylate monomers dissolved in fluid-layer smectic A and smectic C liquid crystal (LC) hosts exhibited significant spatial segregation and orientation that depend strongly on monomer structure. Small, flexible monomers such as 1,6-hexanediol diacrylate (HDDA) oriented parallel to the smectic layers and intercalated, whereas rod-shaped mesogen-like monomers such as 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) oriented normal to the smectic layers and collected within them. Such spatial segregation caused by the smectic layering dramatically enhanced photopolymerization rates; for HDDA, termination rates were reduced, whereas for C6M, both the termination and propagation rates were increased. These polymerization precursor structures suggest novel materials-design paradigms for gel LCs and nanophase-separated polymer systems.     

Evolution of Acoustic Behaviour in African Bufo (Anura: Bufonidae)

Mating calls are known for 29 species of African Bufo belonging to 11 species groups. Twenty-five African species, representing eight species groups (including four groups or complexes having 2N=22) have calls which Martin (1972) termed Type I. This call type is also found in Schismaderma carens, Nectophrynoides tornieri and N. occidentalis. It is known in only four species of Bufo outside Africa and in Odontophrynus americanus which is thought to be closely related to leptodactylids that gave rise to the genus Bufo. Four African species of Bufo have Type II calls.

Geographic distribution of three call types indicates large radiations of one or two call types in South America, North America and Africa. The European and Asian Bufo faunas appear to be derived primarily from American radiations.

The radiation of bufonids in Africa appears to be equal to that of South America. An explanation of this may be that Bufo or its progenitor evolved prior to the continental separation of South America and Africa.     

Lesions caused by the hepatic trematode, Metorchis conjunctus, Cobbold, 1860. A comparative study in carnivora

Abstract— Lesions caused by the hepatic trematode, Metorchis conjunctus Cobbold, 1860, in five species of Carnivora, the dog, cat, raccoon, mink, and gray fox were compared. Marked hyperplasia of the mucosa of the intrahepatic bile ducts and gall bladder was found. The inflammatory reaction consisted principally of lymphocytes and plasma cells with a few eosino-phils. Verminous granulomas were also present and incited a local eosinophilic response. With heavy infections, the raccoon developed a severe cirrhosis, and osseous metaplasia was found in the bile ducts of one mink. Résumé— On compare les lésions provoqueées par un trématode hépatique, Metorchis conjunctus (Cobbold, 1860) chez cinq espèces de carnivores, le chien, le chat, le raton laveur, la loutre et le renard gris. On a trouvé une hyperplasie importante de la muqueuse des canaux biliaries intrahépatiques et de la muqueuse de la vésicule biliare. La réaction inflammatoire comportait surtout des lymphocytes, des plasmocytes mais peu de cellules éosinophiles. On a trowé aussi des granulomes vermineux ayant entraïné une réaction épsinophilique locale. En cas d'infestation massive, le raton peut présenter une cirrhose intense et on a pu observer la métaplasie osseuse des canaux biliaires chez une loutre. Zusammenfassung— Es werden Lasionen, die bei fünf Fleischfresserarten, dem Hund, der Katze dem Waschbären, dem Nerz und dem Graufuchs, durch Leberegel, Metorchis conjunctus Cobbold, 1860, verursacht waren, miteinander verglichen. Eine ausgesprochene Hyperplasie der Schleimhäute wurde in den intrahepatischen Gallengängen und der Gallenblase beobachtet. Die entzündliche Reaktion bestand hauptsächlich aus Lympho-zyten und Plasmazellen, sowie vereinzelten Eosinophilen. Außerdem waren verminöse Granulome vorhanden, die örtlich eine eosinophile Reaktion hervorriefen. Bei schweren Infektionen entwickelte sich bei den Waschbxren eine hochgradige Zirrhose, und in den Gallengängen eines Nerses wurden knochige Metaplasien gefunden.     

Tropospheric ozone pollution reduces the yield of African crops

Northern, Southern and Equatorial Africa have been identified as among the regions most at risk from very high ozone concentrations. Whereas we know that many crop cultivars from Europe, north America and Asia are sensitive to ozone, almost nothing is known about the sensitivity of staple food crops in Africa to the pollutant. In this study cultivars of the African staple food crops, Triticum aestivum (wheat), Eleusine coracana (finger millet), Pennisetum glaucum (pearl millet) and Phaseolus vulgaris (bean) were exposed to an episodic ozone regime in solardomes in order to assess whether African crops are sensitive to ozone pollution. Extensive visible leaf injury due to ozone was shown for many cultivars, indicating high sensitivity to ozone. Reductions in total yield and 1,000-grain weight were found for T. aestivum and P. vulgaris, whereas there was no effect on yield for E. coracana and P. glaucum. There were differences in sensitivity to ozone for different cultivars of an individual crop, indicating that there could be possibilities for either cultivar selection or selective crop breeding to reduce sensitivity of these crops to ozone.     

Nudging fisheries and aquaculture research towards food systems

Food system is a powerful concept for understanding and responding to nutrition and sustainability challenges. Food systems integrate social, economic, environmental and health aspects of food production through to consumption. Aquatic foods are an essential part of food systems providing an accessible source of nutrition for millions of people. Yet, it is unclear to what degree research across diverse disciplines concerning aquatic foods has engaged food systems, and the value this concept has added. We conducted a systematic review of fisheries, aquaculture and aquatic food literature (2017–2019) to determine the following: the characteristics of this research; the food systems components and interrelations with which research engaged; and the insights generated on nutrition, justice, sustainability and climate change. Sixty five of the 88 reviewed articles focussed on production and supply chains, with 23 considering human nutrition. Only 13% of studies examined low- and middle-income countries that are most vulnerable to undernutrition. One third of articles looked beyond finfish to other aquatic foods, which illuminated values of local knowledge systems and diverse foods for nutrition. When aggregated, reviewed articles examined the full range of food system drivers—biophysical and environmental (34%), demographic (24%) and socio-cultural (27%)—but rarely examined interactions between drivers. Future research that examines a diversity of species in diets, system-wide flows of nutrients, trade-offs amongst objectives, and the nutritional needs of vulnerable social groups would be nudging closer to the ambitions of the food systems concept, which is necessary to address the global challenges of equity, nutrition and sustainability.     

Designing fecal pellet surveys for snowshoe hares

Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. Fecal pellet counts are often used as an index of density or habitat use of snowshoe hares, Lepus americanus, but previous surveys have used different plot types and sample sizes, leading to problems comparing results from different studies and questions about the inferential power of each study. In this paper, we use field data and simulations to examine how the precision, bias, and efficiency of four commonly used plot types vary with plot type, pellet density, and sample size. Although no one plot type was consistently superior, we recommend thin rectangles (5.08 cm × 305 cm (2 in. × 10 ft), 0.155 m²) or 1 m² circles over 0.155 m² circles or 10 cm × 10 m (1 m²) rectangles. We recommend that researchers explicitly address the power of their survey design to detect different pellet densities, because much larger sample sizes are needed at low pellet densities than at high pellet densities to obtain similar precision. Small sample sizes are also much more likely to be biased, which could lead to incorrect inferences about management of snowshoe hare populations. Both uncleared and cleared plots performed well and will have value in different research contexts.     

Selection for resistance to the maize weevil in kernels of maize

Summary Significant differences in progeny numbers, weights and developmental periods of weevils were found among maize slections. Resistance to weevil attack increased through selection in dent types but not in flint types. Resistance was located in the pericarp, which is maternal tissue. In the nearly homozygous dent lines the pericarp and embryo are genetically similar. Lack of success in the selection for resistance in the flint sources is explained by the difference in genotypes between pericarp and embryo, as little inbreeding had occurred. Some degree of antibiosis was found in the endosperm.Contribution No. 1095, Department of Entomology, No. 1312 Department of Agronomy, Kansas Agricultural Experiment Station, Manhattan, Kansas 66506, USA. Present address: CIAT, Apdo, Aereo 6713, Cali, Colombia.