Early food production in the Sahel of Burkina Faso

This paper is concerned with the transition from hunting and gathering to food production in West Africa, based on evidence from the Sahel Zone of Burkina Faso compiled by field research during the last years. Our study intends to enhance the knowledge about the West African versions of this transition, traditionally seen as one of the most fundamental changes in human prehistory. Embedded in an interregional program the Sahel Zone of Burkina Faso has proved to be one of its most unexpected examples

Produktion von Bromisotopen und ihre Anwendung zur Entwicklung radiobromierter Adenosin-Rezeptorliganden

For a re-evaluation of production routes of the medically interesting radioisotopes $^{75}$Br, ${76}$Br,$^{77}$Br and $^{82}$Br, cross sections of deuteron induced reactions on natural selenium weremeasured in the energy range up to 41 MeV. Here, measurements of nuclear reactions on$^{nat}$Se leading to the formation of the neutron deficient isotopes were done for the first time.The new data of the $^{nat}$Se(d,xn)$^{75}$Br process indicate that the promising PET nuclide $^{75}$Br can be produced via the $^{74}$Se(d,n)-reaction in isotopically pure form using deuterons from 10 MeVupwards. Assuming an enrichment of 100 % $^{74}$Se, a sufficient production yield of ca.1 GBq/$\mu$Ah $^{75}$Br is to be expected by covering the energy range 15 $\rightarrow$ 2 MeV. In comparison to the commonly used $^{76}$Se(p,2n)-route, the (d,n)-reaction proceeds at markedly lowerprojectile energies and the isotopic contamination of longer-lived $^{76}$Br could be avoided. For removing discrepancies in the literature data of$\alpha$-particle induced reactions on arsenic, reaction cross section measurements concerning the nuclear processes $^{75}$As($\alpha$,xn)$^{76,77,78}$Br and $^{75}$As($\alpha$,x)$^{74}$As were performed in the energy range of 8 to 38 MeV and integral productionyields were calculated. Here, the ratio of monitor nuclides $^{67}$Ga/$^{66}$Ga permitted an improveddetermination of the $\alpha$-particle energies as well as the resulting beam current, and thus of theexperimental data. Aiming at routine production of radiobromine, a new high-current selenium based target wasdesigned and the already known dry distillation procedure for the isolation of n.c.a. [*Br]bromine from the target material was optimized. Compared to the conventionally used Cu$_{2}$Se, the new target material NiSe contains a 1.5 times higher amount of selenium, hence resulting in significantly higher production yields. The optimized dry distillation method enables high, reproducible yields of 76 - 86 %. By using a quartz capillary for trapping the radiobromine, the handling of this method was improved and the possibility for (semi-)automation was given. Moreover the volume of the radioactivity solution was significantlyreduced to less than 100 $\mu$l compared to previous approaches. The obtained n.c.a. [*Br]bromide of high radiochemical purity is immediately available for subsequent radiosyntheses. Using this n.c.a. [*Br]bromide solution the radiosynthesis of the first radiobrominated A$_{1}$-adenosine receptor ligand [*Br]CPBPX (8-cyclopentyl-3-[(E)-3-[*Br]bromoprop-2-en-1-yl]-1-propylxanthine) was optimized with respect to the most important reaction parameters. Since the $^{131}$l-analogue [$^{131}$l]CPIPX as well as the $^{18}$F-labelled [$^{18}$F]CPFPX already exist, [*Br]CPBPX closes the gap of lipophilicity in this cyclopentylxanthine series. Under optimum reaction conditions [*Br]CPBPX was obtained in radiochemical yields of 43 ± 7 % with aspecific activity of 8.6 GBq/$\mu$mol. By $\textit{in vitro}$ competition experiments for CPBPX a K$_{l}$-value of 26 nM was determined that indicates a quite good affinity to the target receptor. In autoradiographic binding studies on rat brain slices the radioligand [*Br]CPBPX showed an increased accumulation in brain areas of high A$_{1}$AR density with a specific binding of ca. 20 %. So, with [*Br]CPBPX a new radioligand is available for sytematic pre-clinical evaluation

Production of no-carrier-added radiobromine: new nickel selenide target and optimized separation by dry distillation

Nickel(II) selenide (NiSe) was investigated as a new high-current target material for cyclotron production of radiobromine, as it contains a higher amount of selenium and has a lower melting point than the widely used Cu2Se. Using a slanted target system, NiSe was successfully tested up to beam currents of 16 μA so far. With regard to the isolation of no-carrier-added (n.c.a.) radiobromide from the target material, an improved dry distillation device with high yields of 76% – 86% was developed. The implementation of a special custom-made quartz funnel decreased the dead volume of the apparatus and a quartz capillary for trapping the radiobromine allowed to concentrate the radioactivity in a small volume of less than 100 μL of 0.1 M NaOH, ready for immediate subsequent radiosyntheses. Thus, the new apparatus improves the handling of the isolation procedure and the radioactive product. The radiochemical purity of the resulting solution of n.c.a. [*Br]bromide was verified by radio-IC where no other species were detected

A question of rite—pearl millet consumption at Nok culture sites, Nigeria (second/first millennium BC)

International audienceThe Nok culture in central Nigeria, dated 1500-1 cal bc, is known for its famous terracotta sculptures. We here present a study on > 11,000 botanical macro-remains from 50 sites, including 343 samples from Nok contexts and 22 samples dating between cal ad 100 and 400, after the end of the Nok culture. With 9,220 remains, pearl millet (Cenchrus americanus (L.) Morrone, syn. Pennisetum glaucum (L.) R.Br.) is dominant in the Nok samples, followed by cowpea (Vigna unguiculata (L.) Walp.), Canarium schweinfurthii Engl., Nauclea latifolia Sm. (syn. Sarcocephalus latifolius (Sm.) E.A.Bruce), wild fruit trees and wild Poaceae. The pearl millet remains consist exclusively of charred caryopses; chaff remains are completely absent. Because we studied all size fractions, including the small 0.5 mm fractions usually containing the involucres, bristles and husks, the absence of pearl millet chaff is real, excluding a methodological explanation, and distinguishes Nok from contemporary other West African sites. We propose that most excavated Nok sites were consumer sites where clean grain was brought in from outside and consumed in a ritual context connected with feasting. This is in line with the archaeological evidence from the larger excavated sites with stone-pot arrangements that are interpreted as ritual places related to mortuary practices. In addition to the known southward branches of pearl millet diffusion from the Sahara we propose a new, hitherto unknown branch directly from the central Sahara to the central Nigerian savannas

Production of n.c.a. radiobromide: new nickel selenide target and optimized separation by dry distillation

Introduction Radioisotopes of bromine are of special interest for nuclear medical applications. The positron emitting isotopes 75Br (T½ = 1.6 h; β+ = 75.5 %) and 76Br (T½ = 16.2 h; β+ = 57 %) have suitable decay properties for molecular imaging with PET, while the Auger electron emitters 77Br (T½ = 57.0 h) and 80mBr (T½ = 4.4 h) as well as the β−-emitter 82Br (T½ = 35.3 h) are useful for internal radiotherapy. 77Br is additionally suited for SPECT. The isotopes 75Br, 76Br and 77Br are usually produced at a cyclotron either by 3He and α-particle induced reactions on natural arsenic or by proton and deuteron induced reactions on enriched selenium isotopes [1]. As target mate-rials for the latter two reactions, earlier ele-mental selenium [2] and selenides of Cu, Ag, Mn, Mo, Cr, Ti, Pb and Sn were investigated [cf. 3–7]. Besides several wet chemical separation techniques the dry distillation of bromine from the irradiated targets was investigated, too [cf. 2, 4, 5]. However, the method needs further development. Nickel selenide was investigated as a promising target to withstand high beam currents, and the dry distillation technique for the isolation of n.c.a. radiobromine from the target was optimized. Material and Methods Crystalline Nickel-(II) selenide (0.3–0.5 g) was melted into a 0.5 mm deep cavity of a 1 mm thick Ni plate covered with a Ni grid. NiSe has a melting point of 959 °C. For development of targeting and the chemical separation, natural target material was used. Irradiations of NiSe were usually performed with protons of 17 MeV using a slanting water cooled target holder at the cyclotron BC1710 [8]. For radiochemical studies a beam current of 3 µA and a beam time of about 1 h were appropriate. To separate the produced no-carrier-added (n.c.a.) radiobromine from the target material a dry distillation method was chosen. The apparatus was developed on the basis of a dry distillation method for iodine [cf. 9,10] and optimized to obtain the bromine as n.c.a. [*Br]bromide in a small volume of sodium hydroxide solution. Changing different components of the apparatus, the dead volume could be minimized and an almost constant argon flow as carrier medium was realized. Various capillaries of platinum, stainless steel and quartz glass with different diameters and lengths were tested to trap the radiobromine. Results and Conclusion Nickel selenide proved successful as target material for the production of radiobromine by proton irradiation with 17 MeV protons. The target was tested so far only at beam currents up to 10 µA, but further investigations are ongoing. The optimized dry distillation procedure allows trapping of 80–90 % of the produced radiobromine in a capillary. For this purpose quartz glass capillaries proved to be most suitable. After rinsing the capillary with 0.1 M NaOH solution the activity can be nearly completely obtained in less than 100 µL solution as [*Br]bromide immediately useable for radiosynthesis. So, the overall separation yield was estimated to 81 ± 5 %. The radionuclidic composition and activity of the separated radiobromide was measured by γ-ray spectrometry. Due to the use of natural selenium the determination of the isotopic purity was not meaningful, but it could be shown that the radiobromine was free from other radioisotopes co-produced in the target material and the backing. The radiochemical purity as well as the specific activity were determined by radio ionchromatography. Further experiments using NiSe produced from nickel and enriched selenium are to be per-formed. The isotopic purity of the produced respective radiobromide, the production yield at high beam currents and the reusability of the target material have to be studied