On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

The objectives of this work are to examine the causes of the breakdown in the photovoltaic power systems, to propose strategies to solve them, and to evaluate the field lifetime of some elements of the PV systems. The data analyzed were obtained from maintenance records and measurements over a period of 9 years (from 2007 to 2015) for the backup PV systems and 2 years (from 2016 to 2018) for photovoltaic water pumping (PVWPS) systems. It appears from this analysis that 29% of the batteries went bad (leading to curative intervention); this contributed to about 64.9% of the total breakdown registered. Using the failure modes, effects and criticality analysis (FMECA) method for PVWPS, criticality is 252, 402, and 504 for inverters, PV module, and motor pump, respectively. This demonstrates that motor pumps are more sensitive than other elements in the PVWPS. This study also permitted not only to evaluate the quantity of preventive and corrective maintenance impacts on solar PV systems but also to propose maintenance strategies to rapid diagnosis of PV systems

Dysfunctional TRPM8 signalling in the vascular response to environmental cold in ageing.

Ageing is associated with increased vulnerability to environmental cold exposure. Previously, we identified the role of the cold-sensitive transient receptor potential (TRP) A1, M8 receptors as vascular cold sensors in mouse skin. We hypothesised that this dynamic cold-sensor system may become dysfunctional in ageing. We show that behavioural and vascular responses to skin local environmental cooling are impaired with even moderate ageing, with reduced TRPM8 gene/protein expression especially. Pharmacological blockade of the residual TRPA1/TRPM8 component substantially diminished the response in aged, compared with young mice. This implies the reliance of the already reduced cold-induced vascular response in ageing mice on remaining TRP receptor activity. Moreover, sympathetic-induced vasoconstriction was reduced with downregulation of the α2c adrenoceptor expression in ageing. The cold-induced vascular response is important for sensing cold and retaining body heat and health. These findings reveal that cold sensors, essential for this neurovascular pathway, decline as ageing onsets

The antimicrobial cathelicidin CRAMP augments platelet activation during psoriasis in mice

Platelet-associated complications including thrombosis, thrombocytopenia, and haemorrhage are commonly observed during various inflammatory diseases such as psoriasis. Although several mechanisms that may contribute to the dysfunction of platelets during inflammatory diseases have been reported, knowledge on the primary molecules/mechanisms that underpin platelet-associated complications in such conditions is not fully established. Here, we report the significance of the mouse antimicrobial cathelicidin, mouse cathelicidin-related antimicrobial peptide (mCRAMP) (an orthologue of LL37 in humans), on the modulation of platelet reactivity during psoriasis using Imiquimod-induced psoriasis in mice as an inflammatory disease model for psoriasis vulgaris in humans. The activation of platelets during psoriasis is increased as evidenced by the elevated levels of fibrinogen binding and P-selectin exposure on the surface of platelets, and the level of soluble P-selectin in the plasma of psoriatic mice. The skin and plasma of psoriatic mice displayed increased levels of mCRAMP. Moreover, the plasma of psoriatic mice augmented the activation of platelets obtained from healthy mice. The effect of mCRAMP is partially mediated through formyl peptide receptor 2/3 (Fpr2/3, the orthologue to human FPR2/ALX) in platelets as a significant reduction in their activation was observed when FPR2/ALX-selective inhibitors such as WRW4 or Fpr2/3-deficient mouse platelets were used in these assays. Since the level of antimicrobial cathelicidin is increased in numerous inflammatory diseases such as psoriasis, atherosclerosis, and inflammatory bowel disease, the results of this study point towards a critical role for antimicrobial cathelicidin and FPR2/ALX in the development of platelet-related complications in such diseases

The endogenous antimicrobial cathelicidin LL37 induces platelet activation and augments thrombus formation

Platelet-associated complications including thrombosis, thrombocytopenia and haemorrhage are commonly observed during various inflammatory diseases such as psoriasis, sepsis and inflammatory bowel disease. Despite the reported evidence on numerous mechanisms/molecules that may contribute to the dysfunction of platelets, the primary mechanisms that underpin platelet-associated complications during inflammatory diseases are not fully established. Here, we report the discovery of formyl peptide receptor 2, FPR2/ALX in platelets, and its primary role in the development of platelet-associated complications via ligation with its ligand, LL37. LL37 acts as a powerful endogenous antimicrobial peptide but it also regulates innate immune responses. We demonstrate the impact of LL37 in the modulation of platelet reactivity, haemostasis, and thrombosis. LL37 activates a range of platelet functions, enhances thrombus formation, and shortens the tail bleeding time in mice. By utilising a pharmacological inhibitor and Fpr2/3 (an orthologue of human FPR2/ALX)-deficient mice, the functional dependence of LL37 on FPR2/ALX was determined. Since the level of LL37 is increased in numerous inflammatory diseases, these results point towards a critical role for LL37 and FPR2/ALX in the development of platelet-related complications in such diseases. Hence, a better understanding of the clinical relevance of LL37 and FPR2/ALX in diverse pathophysiological settings will pave the way for the development of improved therapeutic strategies for a range of thromboinflammatory diseases

Evidence That a TRPA1-Mediated Murine Model of Temporomandibular Joint Pain Involves NLRP3 Inflammasome Activation

From MDPI via Jisc Publications RouterHistory: accepted 2021-10-14, pub-electronic 2021-10-23Publication status: PublishedFunder: Versus Arthritis; Grant(s): 21541This study investigates the role of transient receptor potential ankyrin 1 (TRPA1) in murine temporomandibular joint (TMJ) inflammatory hyperalgesia and the influence of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. Two distinct murine models of TMJ pain and inflammation (zymosan and CFA) were established. Spontaneous pain-like behaviours were observed as unilateral front paw cheek wipes. Ipsilateral cheek blood flow was used as a measure of ongoing inflammation, which, to our knowledge, is a novel approach to assessing real-time inflammation in the TMJ. Joint tissue and trigeminal ganglia were collected for ex vivo investigation. Both zymosan and CFA induced a time-dependent increase in hyperalgesia and inflammation biomarkers. Zymosan induced a significant effect after 4 h, correlating with a significantly increased IL-1β protein expression. CFA (50 µg) induced a more sustained response. The TRPA1 receptor antagonist A967079 significantly inhibited hyper-nociception. The NLRP3 inhibitor MCC950 similarly inhibited hyper-nociception, also attenuating inflammatory markers. In the trigeminal ganglia, CFA-induced CGRP expression showed trends of inhibition by A967079, whilst lba1 immunofluorescence was significantly inhibited by A967079 and MCC950, where the effect of TRPA1 inhibition lasted up to 14 days. Our results show that stimulation of TRPA1 is key to the TMJ pain. However, the inflammasome inhibitor exhibited similar properties in attenuating these pain-like behaviours, in addition to some inflammatory markers. This indicates that in addition to the therapeutic targeting of TRPA1, NLRP3 inhibition may provide a novel therapeutic strategy for TMJ inflammation and pain

Psoriatic skin inflammation induces a pre-diabetic phenotype via the endocrine actions of skin secretome

Objective: Psoriasis is a chronic inflammatory skin disease that is thought to affect ∼2% of the global population. Psoriasis has been associated with ∼30% increased risk of developing type 2 diabetes (T2D), with numerous studies reporting that psoriasis is an independent risk-factor for T2D, separate from underlying obesity. Separately, studies of skin-specific transgenic mice have reported altered whole-body glucose homeostasis in these models. These studies imply a direct role for skin inflammation and dysfunction in mediating the onset of T2D in psoriasis patients, potentially via the endocrine effects of the skin secretome on key metabolic tissues. We used a combination of in vivo and ex vivo mouse models and ex vivo human imiquimod (IMQ) models to investigate the effects of psoriasis-mediated changes in the skin secretome on whole-body metabolic function. Methods: To induce psoriatic skin inflammation, mice were topically administered 75 mg of 5% IMQ cream (or Vaseline control) to a shaved dorsal region for 4 consecutive days. On day 5, mice were fasted for glucose and insulin tolerance testing, or sacrificed in the fed state with blood and tissues collected for analysis. To determine effects of the skin secretome, mouse skin was collected at day 5 from IMQ mice and cultured for 24 h. Conditioned media (CM) was collected and used 1:1 with fresh media to treat mouse explant subcutaneous adipose tissue (sAT) and isolated pancreatic islets. For human CM experiments, human skin was exposed to 5% IMQ cream for 20 min, ex vivo, to induce a psoriatic phenotype, then cultured for 24 h. CM was collected, combined 1:1 with fresh media and used to treat human sAT ex vivo. Markers of tissue inflammation and metabolic function were determined by qPCR. Beta cell function in isolated islets was measured by dynamic insulin secretion. Beta-cell proliferation was determined by measurement of Ki67 immunofluorescence histochemistry and BrDU uptake, whilst islet apoptosis was assessed by caspase 3/7 activity. All data is expressed as mean ± SEM. Results: Topical treatment with IMQ induced a psoriatic-like phenotype in mouse skin, evidenced by thickening, erythema and inflammation of the skin. Topical IMQ treatment induced inflammation and signs of metabolic dysfunction in sub-cutaneous and epidydimal adipose tissue, liver, skeletal muscle and gut tissue. However, consistent with islet compensation and a pre-diabetic phenotype, IMQ mice displayed improved glucose tolerance, increased insulin and c-peptide response to glucose, and increased beta cell proliferation. Treatment of sAT with psoriatic mouse or human skin-CM replicated the in vivo phenotype, leading to increased inflammation and metabolic dysfunction in mouse and human sAT. Treatment of pancreatic islets with psoriatic mouse skin-CM induced increases in beta-proliferation and apoptosis, thus partially replicating the in vivo phenotype. Conclusions: Psoriasis-like skin inflammation induces a pre-diabetic phenotype, characterised by tissue inflammation and markers of metabolic dysfunction, together with islet compensation in mice. The in vivo phenotype is partially replicated by exposure of sAT and pancreatic islets to psoriatic-skin conditioned media. These results support the hypothesis that psoriatic skin inflammation, potentially via the endocrine actions of the skin secretome, may constitute a novel pathophysiological pathway mediating the development of T2D

Traditional beliefs in modern society : the case of the Kapsiki blacksmiths of Mogode, Northern Cameroon

This is an essay on the dynamics of the evolution of the Kapsiki blacksmiths group of Mogode. Among the Kapsiki, blacksmiths perform many trades and crafts calling for specialization as funeral, music, divination, magic and medicine, pottery, leatherwork, forging iron and casting brass crucial for people's life. But their position in the society is characterized by a big paradox between them and the others. They are perceived as a low stratum treated and considered by being dirty, dangerous and impure. The main concern of this essay is the investigation into this paradoxical position of the blacksmiths(rehe)and the power circulation among the Kapsiki

Status of renewable energy in Cameroon

Globally, the continuous increase of energy consumption coupled with the depletion of the limited fossil fuel sources and their negative impacts on the environment, has shifted focus towards renewables for a sustainable development. For the last fifteen years, the world has enjoyed renewables generation capacity increases in a double-digit Terawatt-hours range. Although renewables consumption is fast developing in Asia Pacific, Europe and North America, significant coordination efforts are required among stakeholders in sub-Saharan Africans countries such as Cameroon. In 2018, the total final energy consumption in Cameroon was 7.41 Mtoe, 74.22% of which was from biomass, 18.48% from fossil fuels and 7.30% from electricity. Furthermore, 6977 GWh of electricity was produced, 78.29% of which from the major electricity operator (ENEO S.A. Cameroon) and 21.71% from independent producers (GLOBELEQ, ALTAAQA Sinohydro China and AGGREKO). More than three quarter of electricity produced were consumed by industry (57.04%) and residential (20.74%) sectors. The country's installed electricity generation capacity rose to 1402 MW, 56.15% of which was from hydropower, 43.84% from fossil fuels (17.55% from natural gas and 26.29% from oil) and 0.01% from solar photovoltaic. The promotion of renewable energy is an important part of Cameroon's plan to increase energy security and provide job opportunities to the country. Yet, the lack of proactive and long-term renewable energy policy and laws, in addition to less attention paid to renewable energy training and research, financing mechanisms, and unaffordable costs of renewable energy technologies to the poor population are amongst present issues hindering the development of renewable energy in the country. Hence, this paper aims to highlight the present status of renewable energy exploitation and development in Cameroon

Technical and Economic Potentialities of the Development of Electric Wind Pumping Systems in the North Region of Cameroon

International audienceIn the present work, the potential of wind electric pumping systems (WEPS) utilization has been investigated for eight localities of the North Region of Cameroon, using long-term satellite-derived data and measured data at 10 m height above ground level (agl). Statistical indexes of accuracy performed the comparison between measured and satellite-derived data. The results suggested that satellite-derived data can accurately represent measured data. Furthermore, satellite-derived data can be suitable to assess the wind resource when measured ground level data are missing. The two-parameter Weibull Probability distribution function (PDF) and parabolic law were utilized, respectively to model wind speeds characteristics and wind turbines power curve. Four wind turbines (WT), represented by WT1, WT2, WT3 and WT4, with a rated capacity of 20 kW and a 30 m tower, were considered to simulate the power output and energy produced. The results showed that annual power densities at 10 m agl, for Bashéo, Beka, Figuil, Garoua, Pitoa, Poli, Rey-Bouba and Touboro were, respectively, 29.74, 17.45, 33.64, 17.94, 22.28, 11.99, 16.46 and 15.98 W/m2, while corresponding energy densities were 0.71, 0.42, 0.81, 0.43, 0.53, 0.29, 0.40 and 0.38 kWh/m2/day, in that order. Annual average frequencies for wind speeds greater or equal to WT’s cut-in wind speeds for each of the eight sites were determined. The greatest probability of observing higher wind speeds is for the site of Figuil, .This site showed the best combination of capacity factors (CF), costs of energy (COE), costs of water (COW) and flow rate capacity, At the opposite, the greatest probability of observing lower speeds is for the site of Poli that displayed the worst values of CF, COE, COW and flow rate capacity independently of the WT used. As a result, choosing WT for low wind speeds sites, would require to combine location wind resource and WT characteristics such as cut-in and rated wind speeds in order to take full advantage of costs of energy and water produced