Cashew cultivation in Guinea-Bissau – risks and challenges of the success of a cash crop

In recent decades a boom in cashew (Anacardium occidentale)cultivation has taken place in Guinea-Bissau, leading to the replacement of traditional slash-and-burn agriculture by a cash crop. As a result, the country is currently one of the world’s largest producers of raw cashew nuts and the cashew sector has acquired enormous importance in Guinea-Bissau’s economy. Changes induced by the cashew boom at social and environmental levels are yet to be analyzed and understood. The present study provides an account of the process of cashew expansion in Guinea-Bissau, reviews the current situation and discusses its future prospects. The cashew tree was introduced into the country by the Portuguese in the XIXth century, but only effectively expanded in the mid-1980s. It is largely cultivated by small farmers around villages and also plays a role in land ownership, since land tenure practices are linked to the planting of trees. The effects of this cashew boom on habitat fragmentation, fire regimes and biodiversity are still to be assessed. On the other hand, the spread of pests and diseases is becoming a problem. Strong dependence on a single cash crop also renders the country vulnerable to market fluctuations, entailing risks to local producers and the national economy. In the medium term, losses of export earnings can occur, which may impact the living standards and food security of Bissau-Guineans both in urban and rural areas

Selective augmentation of striatal functional connectivity following NMDA receptor antagonism: implications for psychosis

The psychotomimetic effect of the N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine is thought to arise from a functional modulation of the brain's fronto-striato-thalamic (FST) circuits. Animal models suggest a pronounced effect on ventral ‘limbic' FST systems, although recent work in patients with psychosis and high-risk individuals suggests specific alterations of dorsal ‘associative' FST circuits. Here, we used functional magnetic resonance imaging to investigate the effects of a subanesthetic dose of ketamine on measures of functional connectivity as indexed by the temporal coherence of spontaneous neural activity in both dorsal and ventral FST circuits, as well as their symptom correlates. We adopted a placebo-controlled, double-blind, randomized, repeated-measures design in which 19 healthy participants received either an intravenous saline infusion or a racemic mixture of ketamine (100 ng/ml) separated by at least 1 week. Compared with placebo, ketamine increased functional connectivity between the dorsal caudate and both the thalamus and midbrain bilaterally. Ketamine additionally increased functional connectivity of the ventral striatum/nucleus accumbens and ventromedial prefrontal cortex. Both connectivity increases significantly correlated with the psychosis-like and dissociative symptoms under ketamine. Importantly, dorsal caudate connectivity with the ventrolateral thalamus and subthalamic nucleus showed inverse correlation with ketamine-induced symptomatology, pointing to a possible resilience role to disturbances in FST circuits. Although consistent with the role of FST in mediating psychosis, these findings contrast with previous research in clinical samples by suggesting that acute NMDAR antagonism may lead to psychosis-like experiences via a mechanism that is distinct from that implicated in frank psychotic illness

Polarity-dependent forming in ion bombarded amorphous silicon memory devices

Polarity-dependent forming in ion bombarded metal-semiconductor-metal (MSM) memory devices of hydrogenated amorphous silicon is reported. It is shown that prior to ion bombardment, current transport in the MSM devices is asymmetric and is controlled by the Schottky barriers at two MS junctions. Upon bombardment, however, there is a bulk component to the current and the I -V characteristics of the devices become symmetric at low bias voltages. The forming voltage in the bombarded devices shows polarity dependence. For positive bias applied on the top contact, we find that devices form at the same electric field independent of the thickness of the amorphous silicon while for negative voltage on the top contact, the electric field needed for forming increases with the thickness. A model involving the difference in energy deposition and heat sinking for the two polarities is proposed

Polarity-Dependent Forming in Ion Bombarded Amorphous Silicon Memory Devices

Polarity-dependent forming in ion bombarded metal-semiconductor-metal (MSM) memory devices of hydrogenated amorphous silicon is reported. It is shown that prior to ion bombardment, current transport in the MSM devices is asymmetric and is controlled by the Schottky barriers at two MS junctions. Upon bombardment, however, there is a bulk component to the current and the I-V characteristics of the devices become symmetric at low bias voltages. The forming voltage in the bombarded devices shows polarity dependence. For positive bias applied on the top contact, we find that devices form at the same electric field independent of the thickness of the amorphous silicon while for negative voltage on the top contact, the electric field needed for forming increases with the thickness. A model involving the difference in energy deposition and heat sinking for the two polarities is proposed</p

Quantitative CE analysis of punicalagin in <i>Combretum aculeatum</i> extracts traditionally used in Senegal for the treatment of tuberculosis

Mycobacterium tuberculosis is the causative agent of tuberculosis, an infectious bacterial disease, which most commonly affects the lungs. In the search for novel active compounds or medicines against tuberculosis, an ethnopharmacological survey combined with a host‐pathogen assay has recently highlighted the potency of an aqueous extract of Combretum aculeatum. C. aculeatum is used in traditional medicine and has demonstrated a significant in vitro antimycobacterial activity. Punicalagin, an ellagitannin, was isolated and found to be related to the biological activity of the extract. An analytical method for the evaluation of punicalagin in C. aculeatum was developed by capillary electrophoresis. After method optimization, the quantification of punicalagin was achieved for the evaluation of various plant extracts to determine the content of punicalagin related to the extraction modes and conditions, origin of the plant material, and harvesting period. The developed method demonstrated that the leaves presented the highest punicalagin content compared to the seeds and stems. A decoction of 30 min in boiling water was found to be the best extraction mode of C. aculeatum