Determination of Bicarbonate in Substrate Extracts Using Back‐Titration and the Gran Plot Approach

Abstract

The back‐titration procedure, associated with the Gran Plot method to detect the process end point, was compared with other volumetric procedures for the potentiometric acid‐base titration determination of bicarbonate and was explored as a tool for the determination of the bicarbonate content in substrates used as growing media. This procedure was compared with the second derivative approach as well as with continuous titration with standard HCl on the extract solution (“direct measurement”), until reaching pH 4.0. By using known standard samples, it was noted that the results obtained with the second derivative method were both lower and inconsistent, because of the high dilution of both the sample solution and the titrant. On the other hand, the continuous direct titration (until pH 4.0) presents positive errors due to the presence of dissolved CO₂ in the titrated solution. Although comparable in precision, the best performance and accuracy were observed for the back‐titration with the Gran Plot approach. These aspects, associated with its low cost and inherent operational simplicity, permit us to suggest the Gran Plot method as a reliable option for routine determination of bicarbonate in substrate extracts and related materials.     

Current prevalence of Dirofilaria immitis in dogs, cats and humans from the island of Gran Canaria, Spain

The island of Gran Canaria is a hyperendemic area for canine dirofilariasis. The aim of the present study was to provide data on Dirofilaria immitis in dogs, cats, and humans on this island in 2010. The data confirms the prevalence in the overall canine population (19%), with a considerably higher prevalence (43%) in the autochthonous breed of Canarian Warren hound. The prevalence in the feline population (33%) is higher than that of the canine population, and the existence of specific D. immitis antibodies in the inhabitants of the island of Gran Canaria (12%) is confirmed. In both cats and humans, the prevalence, according to the different climate areas on the island, is related to the prevalence of D. immitis in dogs in the same area, which shows the key epidemiological role played by the canine host with regard to the transmission to other hosts of D. immitis.     

标准加入法在仪器分析中的应用释疑

标准加入法在仪器分析中广泛应用。许多学生在学习标准加入法时遇到一些疑惑与困难,文章针对学生的这些问题作适当解释,对一些相关论点也作适当推导介绍。     

The Costa Rican Association for the Study of Native Forestry Species (CANS)

SUMMARY

In the Gran Sabana of Venezuela and the North Rupununi Savannah of Guyana, protected areas have been established primarily for purposes of conservation. However, both Canaima National Park in Venezuela and the Iwokrama International Centre for Rainforest Conservation and Development in Guyana are multiple use areas where a variety of resource use occurs and/or is planned. Shifting cultivation by the indigenous population is currently both the most common use of the forest and the use of longest duration in both areas. Surveys were conducted of paired primary and secondary forests in order to test the hypothesis that traditional, dispersed shifting cultivation with long fallows and no post-cultivation disturbance is sustainable, resulting in the eventual re-establishment of diverse secondary forests. Interviews and observations of agricultural practices and surveys of agricultural fields were conducted to determine the contemporary forest use practices and the extent to which traditional practices have changed. Results indicate that even dispersed, long fallow shifting cultivation requires careful management and several disturbance-free decades before diversity levels in secondary forests approach those in old growth. Further, that the process of integration and cultural “development” has destabilized this traditionally sustainable system in some areas. A central assumption of the paper is that with an understanding of the impacts of shifting cultivation and of the conditions under which it is sustainable, informed decisions about protected area management can be made. The data provide valuable and hitherto missing information on the levels of forest disturbance that can be sustained in the two protected areas while still meeting conservation goals.     

白头鹤营养需要及消化率的初测

通过消化试验的方法,对白头鹤在越冬前期饲料的营养需要进行分析。实验测得,白头鹤对饲料的干物质、粗蛋白、粗脂肪、粗纤维、无氮浸出物(NFE)、消化能的表观消化率分别是:84.62±2.97、85.87±2.50、91.11±2.46、76.02±5.85、81.41±4.68、87.25±2.45％;同时也测得,白头鹤对可消化蛋白、可消化脂肪、可消化无氮浸出物和消化能的需要量(每日每千克体重)分别是:14.626±2.684g、4.564±1.151g、17.356±5.239g和884.816±223.947 KJ,该时期饲料中粗蛋白,粗脂肪、无氮浸出物,消化能要分别达到(按每日每千克体重计):17.033g,5.003g,21.319g,1014.116 KJ,才能满足白头鹤正常的营养需要。     

Spatial and temporal variability of the two main caught species of an artisanal trap fishery in an oceanic island

1. This study analysed the catches of trap fishing in the Canary Archipelago, NE Atlantic Ocean. This study was conducted from October 2016 to September 2017, April to November 2018 and September 2020, in five ports (San Cristóbal, Taliarte, Castillo del Romeral, Arguineguín and Mogán).
2. The primary gear were traps with small mesh size (31.6 mm) and large mesh size (50.8 mm). A total of 2587 small mesh size traps and 141 large mesh size traps were analysed from 20- to 130-m depth.
3. The main target species were Dentex gibbosus and Stephanolepis hispidus.
4. Catches of traps with large mesh size showed D. gibbosus above first maturity and S. hispidus in small mesh size traps. Both species exhibit larger specimens during reproductive periods.
5. The most effective traps for D. gibbosus (large mesh) were located on the western coast (>30-m depth), with the highest catch per unit of effort (CPUE) in Mogán (857.7 g trap⁻¹ day⁻¹). The most effective traps for S. hispidus (small mesh) were located in southern areas, especially in sandy habitats (124.9 g trap⁻¹ day⁻¹ in Castillo del Romeral, 102.9 g trap⁻¹ day⁻¹ in Arguineguín).
6. The highest catchability of D. gibbosus was observed in April (CPUE of 962.8 g trap⁻¹ day⁻¹), and the highest catchability of S. hispidus was found in June (CPUE of 165.9 g trap⁻¹ day⁻¹).
7. The traps with small mesh size showed a great selectivity of sizes for S. hispidus; though high catch rates of immature specimens of D. gibbosus pose a threat to species conservation.
8. The management recommendations' proposed measures include revising minimum catch sizes for both species. Additionally, we suggested depth limitations for mesh sizes of traps.
9. The study highlights the need for new management strategies to ensure the conservation of targeted demersal species, with special emphasis on addressing the threat posed by small mesh sizes to immature D. gibbosus.
10. The findings provide valuable insights for adapting fishery management practices to sustainably conserve the targeted species in the Canary Archipelago.