Long-Distance Trade-Routes in Central Africa

1962 ◽  
Vol 3 (3) ◽  
pp. 375-390 ◽  
Author(s):  
J. Vansina
Keyword(s):  
Raw Materials ◽  
Central Africa ◽  
Long Distance ◽  
Very Old ◽  
Local Markets ◽  
Trade Routes ◽  
Alive Today ◽  
Different Types

The structure of indigenous trade in Central Africa makes it necessary to distinguish between three different types of trade. There is first the local trade from village to village within a given population. The goods exchanged are generally specialized products from local industry, and the exchange comes about because some villages possess supplies of raw materials which are not available to others, e.g. pottery clay, or because they are inhabited by specialists such as smiths or woodcarvers who are not available in others. This type of trade is conducted in local markets, and generally speaking, currency of some sort is in use. It is still alive today, and one can assume that it is very old, since such a system shows little dynamism. The necessities remain the same; the organization is simple and efficient.

Early trade and raw materials in South Central Africa

1969 ◽  
Vol 10 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Brian M. Fagan
Keyword(s):  
Iron Age ◽  
Raw Materials ◽  
Central Africa ◽  
Future Research ◽  
Long Distance ◽  
Regional Trade ◽  
Archaeological Evidence ◽  
South Central ◽  
Iron Copper

Three raw materials were essential to Iron Age peoples in South Central Africa: iron, copper and salt. This paper discusses some of the archaeological evidence for the development of regional and long-distance trade in these commodities during the earlier Iron Age. A distinction is drawn between regional trade in items for which there is local demand, and longer distance commerce in raw materials, which may have been conducted with the aid of some standardized units of monetary significance.The big question for future research is that of assessing the degree to which the more sophisticated centres of metallurgy and trade affected those societies, living outside the immediate area, whose technologies and economies were less highly developed.

Isolation and Diagnosis of Fungi from Samples of Spices in the City of Nasiriya

2020 ◽  
pp. 7-9
Keyword(s):  
Chronic Diseases ◽  
Dilution Method ◽  
Local Markets ◽  
White Pepper ◽  
Black And White ◽  
Different Types ◽  
Potential Risks ◽  
The City ◽  
Isolated Species

Examination of (35) samples of spices obtained from local markets for the purposes of isolating and diagnosing fungi growing on them. Anine isolates belonging to 13 different types of fungi were diagnosed by the standard dilution method with three replications, and it has been observed that the most samples from which the fungi were isolated is ginger. It was found that the most isolated species of fungi are Penicillium, Aspergillus, and Rizupes spp. A rare colony of fungi was observed, which indicates contamination of the spices under study with the fungus. The present study aims to identify the potential risks of the presence of fungi in spices and what may result from mycotoxins that may be the cause of many chronic diseases as a result of using these spices in large quantities. The study recommends limiting the use of contaminated spices, especially ginger, in preparing food and its uses, in addition to other types such as cloves, black and white pepper, and other types of spices found in the local markets, especially the expired ones.

PU composites based on different types of textile fibers

2021 ◽  
pp. 002199832110316
Author(s):  
Nuno Gama ◽  
B Godinho ◽  
Ana Barros-Timmons ◽  
Artur Ferreira
Keyword(s):  
Thermal Conductivity ◽  
Raw Materials ◽  
Natural Fibers ◽  
Tensile Modulus ◽  
High Water ◽  
Textile Fibers ◽  
Synthetic Fibers ◽  
Hydrophilic Nature ◽  
Different Types ◽  
Recycled Composites

In this study polyurethane (PU) residues were mixed with residues of textile fibers (cotton, wool and synthetic fibers up to 70 wt/wt) to produce 100% recycled composites. In addition, the effect of the type of fiber on the performance of the ensuing composites was evaluated. The presence of fibers showed similar effect on the density, reducing the density in the 5.5-9.0% range. In a similar manner, the addition of fillers decreased their thermal conductivity. The 70 wt/wt wool composite presented 38.1% lower thermal conductivity when compared to the neat matrix, a reduction that was similar for the other type of fibers. Moreover, the presence of fillers yields stiffer materials, especially in the case of the Wool based composites, which with 70 wt/wt of filler content increased the tensile modulus of the ensuing material 3.4 times. This was attributed to the aspect ratio and stiffness of this type of fiber. Finally, the high-water absorption and lower thermal stability observed, especially in the case of the natural fibers, was associated with the hydrophilic nature of fibers and porosity of composites. Overall, the results suggest that these textile-based composites are suitable for construction and automotive applications, with the advantage of being produced from 100% recycled raw-materials, without compromised performance.

scholarly journals Modified Nanoclays/Straw Fillers as Functional Additives of Natural Rubber Biocomposites

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 799
Author(s):  
Justyna Miedzianowska ◽  
Marcin Masłowski ◽  
Przemysław Rybiński ◽  
Krzysztof Strzelec
Keyword(s):  
Natural Rubber ◽  
Raw Materials ◽  
Research Work ◽  
Damping Properties ◽  
Main Research ◽  
Functional Additives ◽  
Different Types ◽  
Elastomeric Materials ◽  
Research Goal ◽  
The Impact

Increasingly, raw materials of natural origin are used as fillers in polymer composites. Such biocomposites have satisfactory properties. To ensure above-average functional properties, modifications of biofillers with other materials are also used. The presented research work aimed to produce and characterize elastomeric materials with a straw-based filler and four different types of montmorillonite. The main research goal was to obtain improved functional parameters of vulcanizates based on natural rubber. A series of composites filled with straw and certain types of modified and unmodified nano-clays in various ratios and amounts were prepared. Then, they were subjected to a series of tests to assess the impact of the hybrids used on the final product. It has been shown that the addition of optimal amounts of biofillers can, inter alia, increase the tensile strength of the composite, improve damping properties, extend the burning time of the material and affect the course of vulcanization or cross-linking density.

scholarly journals Differential Tropism in Roots and Shoots of Resistant and Susceptible Cassava (Manihot esculenta Crantz) Infected by Cassava Brown Streak Viruses

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1221
Author(s):  
Samar Sheat ◽  
Paolo Margaria ◽  
Stephan Winter
Keyword(s):  
Virus Replication ◽  
Central Africa ◽  
Streak Virus ◽  
Virus Infections ◽  
Long Distance ◽  
Manihot Esculenta Crantz ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Long Distance Movement ◽  
Brown Streak

Cassava brown streak disease (CBSD) is a destructive disease of cassava in Eastern and Central Africa. Because there was no source of resistance in African varieties to provide complete protection against the viruses causing the disease, we searched in South American germplasm and identified cassava lines that did not become infected with the cassava brown streak viruses. These findings motivated further investigations into the mechanism of virus resistance. We used RNAscope® in situ hybridization to localize cassava brown streak virus in cassava germplasm lines that were highly resistant (DSC 167, immune) or that restricted virus infections to stems and roots only (DSC 260). We show that the resistance in those lines is not a restriction of long-distance movement but due to preventing virus unloading from the phloem into parenchyma cells for replication, thus restricting the virus to the phloem cells only. When DSC 167 and DSC 260 were compared for virus invasion, only a low CBSV signal was found in phloem tissue of DSC 167, indicating that there is no replication in this host, while the presence of intense hybridization signals in the phloem of DSC 260 provided evidence for virus replication in companion cells. In neither of the two lines studied was there evidence of virus replication outside the phloem tissues. Thus, we conclude that in resistant cassava lines, CBSV is confined to the phloem tissues only, in which virus replication can still take place or is arrested.

scholarly journals Quantum repeaters based on concatenated bosonic and discrete-variable quantum codes

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Filip Rozpędek ◽  
Kyungjoo Noh ◽  
Qian Xu ◽  
Saikat Guha ◽  
Liang Jiang
Keyword(s):  
Continuous Variable ◽  
Quantum Codes ◽  
Discrete Variable ◽  
Long Distance ◽  
Concatenated Code ◽  
Different Types ◽  
Optical Modes ◽  
Distance Communication ◽  
Quantum Repeaters ◽  
Quantum Error

AbstractWe propose an architecture of quantum-error-correction-based quantum repeaters that combines techniques used in discrete- and continuous-variable quantum information. Specifically, we propose to encode the transmitted qubits in a concatenated code consisting of two levels. On the first level we use a continuous-variable GKP code encoding the qubit in a single bosonic mode. On the second level we use a small discrete-variable code. Such an architecture has two important features. Firstly, errors on each of the two levels are corrected in repeaters of two different types. This enables for achieving performance needed in practical scenarios with a reduced cost with respect to an architecture for which all repeaters are the same. Secondly, the use of continuous-variable GKP code on the lower level generates additional analog information which enhances the error-correcting capabilities of the second-level code such that long-distance communication becomes possible with encodings consisting of only four or seven optical modes.

Adhesives for the Installation of Cast Basalt Elements on Metal and Comparison of Properties when Using Different Types of Fillers

2021 ◽  
Vol 898 ◽  
pp. 35-41
Author(s):  
Jakub Hodul ◽  
Tomáš Žlebek ◽  
Lenka Mészárosová ◽  
Aleš Jakubík ◽  
Rostislav Drochytka
Keyword(s):  
Construction Industry ◽  
Raw Materials ◽  
Physical And Mechanical Properties ◽  
Mineral Admixtures ◽  
Maximum Efficiency ◽  
Organic Additives ◽  
Metal Base ◽  
Secondary Raw Materials ◽  
Ecological Benefit ◽  
Different Types

The polymeric adhesives for the installation of basalt elements on a metal base are designed primarily for environments with increased chemical and mechanical stress. They are composed of polymer resins (epoxy, polyurethane) as binders, as well as organic additives and mineral admixtures that mainly fulfill the function of filler. In all sectors of today's construction industry, maximum efficiency in the production of materials is required for sustainability purposes, which, however, must never be at the expense of the quality or the required performance. Due to these requirements, great emphasis is placed on the maximum use of secondary raw materials. Talc is used as the primary filler for polymer adhesives. Sawdust, tire rubber, and fly ash are used as secondary raw materials. The use of these in building supplies can positively affect some physical and mechanical properties of polymeric adhesives. Also, the use of secondary raw materials has the above-mentioned ecological benefit. Basic properties, such as bulk density and adhesion to both metallic and basalt elements, were monitored. The details of the cohesion of the adhesive with the bonded material, as well as the distribution of secondary raw materials in the polymer matrix, were assessed microscopically.

scholarly journals Angolan vegetable crops have unique genotypes of potential value for future breeding programmes

2016 ◽  
Vol Volume 112 (Number 3/4) ◽  
Author(s):  
José P. Domingos ◽  
Ana M. Fita ◽  
María B. Picó ◽  
Alicia Sifres ◽  
Isabel H. Daniel ◽  
...  
Keyword(s):  
Strong Dependence ◽  
The Other ◽  
Vegetable Crops ◽  
Cucurbita Maxima ◽  
Capsicum Chinense ◽  
Local Markets ◽  
Potential Value ◽  
Wide Range ◽  
Different Types ◽  
Breeding Programmes

Abstract A survey was carried out in Angola with the aim of collecting vegetable crops. Collecting expeditions were conducted in Kwanza-Sul, Benguela, Huíla and Namibe Provinces and a total of 80 accessions belonging to 22 species was collected from farmers and local markets. Species belonging to the Solanaceae (37 accessions) and Cucurbitaceae (36 accessions) families were the most frequently found with pepper and eggplant being the predominant solanaceous crops collected. Peppers were sold in local markets as a mixture of different types, even different species: Capsicum chinense, C. baccatum, C. frutescens and C. pubescens. Most of the eggplant accessions collected belonged to Solanum aethiopicum L. Gilo Group, the so-called ‘scarlet eggplant’. Cucurbita genus was better represented than the other cucurbit crops. A high morphological variation was present in the Cucurbita maxima and C. moschata accessions. A set of 22 Cucurbita accessions from Angola, along with 32 Cucurbita controls from a wide range of origins, was cultivated in Valencia, Spain and characterised based on morphology and molecularity using a set of 15 microsatellite markers. A strong dependence on latitude was found in most of the accessions and as a result, many accessions did not set fruit. The molecular analysis showed high molecular variability and uniqueness in the collected accessions, as shown by their segregation from the set of global controls. In summary, the material collected is quite valuable because of its uniqueness and the potential of the breeding characteristics it possesses.

Edges and interactions beyond Europe

2018 ◽  
Author(s):  
Peter S. Wells ◽  
Naoise Mac Sweeney
Keyword(s):  
North America ◽  
Iron Age ◽  
North Atlantic ◽  
Cultural Practices ◽  
Raw Materials ◽  
Long Distance ◽  
The North ◽  
First Millennium ◽  
Temperate Europe ◽  
The North Atlantic

Iron Age Europe, once studied as a relatively closed, coherent continent, is being seen increasingly as a dynamic part of the much larger, interconnected world. Interactions, direct and indirect, with communities in Asia, Africa, and, by the end of the first millennium AD, North America, had significant effects on the peoples of Iron Age Europe. In the Near East and Egypt, and much later in the North Atlantic, the interactions can be linked directly to historically documented peoples and their rulers, while in temperate Europe the evidence is exclusively archaeological until the very end of the prehistoric Iron Age. The evidence attests to often long-distance interactions and their effects in regard to the movement of peoples, and the introduction into Europe of raw materials, crafted objects, styles, motifs, and cultural practices, as well as the ideas that accompanied them.

Physicochemical approaches to gold and silver work, an overview: Searching for technologies, tracing routes, attempting to preserve

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Maria F. Guerra
Keyword(s):  
Atmospheric Corrosion ◽  
Raw Materials ◽  
Precious Metals ◽  
Gold Alloys ◽  
Exchange Networks ◽  
Trade Routes ◽  
Physicochemical Methods ◽  
Corrosion Mechanisms ◽  
Challenging Question

Abstract Gold alloys and silver alloys have always been widely employed in the production of significant objects. With high reflectivity, precious metals are perceived as both materials and colours, and can be skilfully combined to produce metallic polychrome effects. Because their structure and composition contain information on their manufacture, use, disclaim and degradation, items in gold and in silver enclose major information on the technologies employed by past societies and on exchange networks. This information can be acquired using appropriate analytical protocols, established according to the nature of the query and the characteristics of the objects. By using physicochemical techniques, it is possible to identify the technologies, materials and tools used by the artisan and, in particular cases, to situate the sources of raw materials and the workshops producing the objects, as well as to follow the trade routes. The aim of this work is to outline major achievements in the study of goldwork and silverwork based on the different physicochemical methods that are available, and to refer the analytical difficulties that have to be faced when studying objects made from precious metals. Based on several examples, three topics are addressed. The first concerns the major role of the techniques of exam when describing shaping, decorating, assembling and finishing; the second considers the search for metallic polychrome effects in some cultural areas; and the third discusses the challenging question of fingerprinting. A fourth section is dedicated to a short reflection on the difficulties related to the identification of the atmospheric corrosion mechanisms of precious metals.

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