The growth performance for most Sub-Sahara African countries was relatively stable in the 1970s but became volatile in the 1990s due to unstable policies and civil unrest. These scenarios were the case for Sierra Leone, the country's growth performance of the 1970s spanning to the 1990s was mixed. Given the welfare implication of economic growth, we investigate key determinants to growth in the event of sustained war in Sierra Leone from 1970 to 2010, using the error correction model (ECM). This study reveals that tertiary education, enrolment rate, population growth rate, employment rate and openness to international trade have positive correlation on growth. High budget deficit, high inflation, exchange rate instability and the civil war that erupted in the country are contributing factors for the economy's poor growth performance. This understanding is important for academics and policy makers in shaping the future economic growth.
State-of-the-art invasive brain-machine interfaces (BMIs) have shown significant promise, but rely on external electronics and wired connections between the brain and these external components. This configuration presents health risks and limits practical use. These limitations can be addressed by designing a fully implantable BMI similar to existing FDA-approved implantable devices. Here, a prototype BMI system whose size and power consumption are comparable to those of fully implantable medical devices was designed and implemented, and its performance was tested at the benchtop and bedside.A prototype of a fully implantable BMI system was designed and implemented as a miniaturized embedded system. This benchtop analogue was tested in its ability to acquire signals, train a decoder, perform online decoding, wirelessly control external devices, and operate independently on battery. Furthermore, performance metrics such as power consumption were benchmarked.An analogue of a fully implantable BMI was fabricated with a miniaturized form factor. A patient undergoing epilepsy surgery evaluation with an electrocorticogram (ECoG) grid implanted over the primary motor cortex was recruited to operate the system. Seven online runs were performed with an average binary state decoding accuracy of 87.0% (lag optimized, or 85.0% at fixed latency). The system was powered by a wirelessly rechargeable battery, consumed ∼150 mW, and operated for >60 h on a single battery cycle.The BMI analogue achieved immediate and accurate decoding of ECoG signals underlying hand movements. A wirelessly rechargeable battery and other supporting functions allowed the system to function independently. In addition to the small footprint and acceptable power and heat dissipation, these results suggest that fully implantable BMI systems are feasible.
Excessive reliance on wheelchairs in individuals with tetraplegia or paraplegia due to spinal cord injury (SCI) leads to many medical co-morbidities, such as cardiovascular disease, metabolic derangements, osteoporosis, and pressure ulcers. Treatment of these conditions contributes to the majority of SCI health care costs. Restoring able-body-like ambulation in this patient population can potentially reduce the incidence of these medical co-morbidities, in addition to increasing independence and quality of life. However, no biomedical solution exists that can reverse this loss of neurological function, and hence novel methods are needed. Brain-computer interface (BCI) controlled lower extremity prostheses may constitute one such novel approach. One able-bodied subject and one subject with paraplegia due to SCI underwent electroencephalogram (EEG) recordings while engaged in alternating epochs of idling and walking kinesthetic motor imagery (KMI). These data were analyzed to generate an EEG prediction model for online BCI operation. A commercial robotic gait orthosis (RoGO) system (suspended over a treadmill) was interfaced with the BCI computer to allow for computerized control. The subjects were then tasked to perform five, 5-min-long online sessions where they ambulated using the BCI-RoGO system as prompted by computerized cues. The performance of this system was assessed with cross-correlation analysis, and omission and false alarm rates. The offline accuracy of the EEG prediction model averaged 86.30% across both subjects (chance: 50%). The cross-correlation between instructional cues and the BCI-RoGO walking epochs averaged across all subjects and all sessions was 0.812±0.048 (p-value <10−4). Also, there were on average 0.8 false alarms per session and no omissions. These results provide preliminary evidence that restoring brain-controlled ambulation after SCI is feasible. Future work will test the function of this system in a population of subjects with SCI. If successful, this may justify the future development of BCI-controlled lower extremity prostheses for free overground walking for those with complete motor SCI. Finally, this system can also be applied to incomplete motor SCI, where it could lead to improved neurological outcomes beyond those of standard physiotherapy.
Abstract Different land use and management actions can affect soil aggregates (SAs) and nutrient stocks, which are crucial for sustainable agriculture. The impacts of various chrono‐sequences on the soil aggregate structure, soil organic carbon (SOC) and nutrients associated with aggregate fractions in wolfberry ( Lycium barbarum L .) plantations are still not fully understood. This study examined the composition and stability of SAs, SOC, total nitrogen (TN), available phosphorus (AP) and exchangeable cations (K + , Na + , Ca 2+ and Mg 2+ ) in bulk soil and various aggregate‐size fractions from five wolfberry plantations with varying ages (1, 4, 6, 10 and 13 years) and a corn field (0 years) in the arid region of northwest Ningxia in China. The results indicated that silt–clay (<53 μm) fractions were dominant in the soil, accounting for 51%–66%, under different plantation ages. The proportion of the macro‐aggregates (>250 μm) increased significantly, by 40%–47%, over the 4 years of wolfberry plantation. Likewise, the soil aggregate stability was improved, and total exchangeable bases (TEB) along with numerous cations concentrations (K + , Na + , Ca 2+ and Mg 2+ ) in SAs were significantly reduced as the wolfberry plantings became older. Both concentrations of SOC and TN in the soil aggregates peaked in the 13th year. The silt–clay fractions stored a considerable amount of SOC and nutrients. However, short‐term (under 6 years) cultivation of wolfberry reduced the stocks of SOC, TN and AP in the soil, while long‐term (over 10 years) cultivation increased them, particularly in macro‐aggregates. These findings indicated that long‐term wolfberry farming had several advantages, such as enhancing soil structure, accumulating SOC and nutrients and ameliorating alkaline soils, especially after 10 years, in the arid northwest of China.
In order to discuss the response of soil nutrient content, stoichiometric ratio, and dynamic nutrient balance to the addition of multiple restrictive nutrients, the correlation between available nutrients and total nutrients in soil, as well as the indication of soil total and available stoichiometric characteristics, were studied in a desert grassland subjected to 4 years of nutrient addition treatments. The Ningxia desert grassland was used as the research object to carry out nitrogen (N) and phosphorus (P) addition experiments. The experiment included four treatments:control (CK), N addition[10 g·(m2·a)-1], P addition[10 g·(m2·a)-1], and NP co-addition (10 g·(m2·a)-1 N+10 g·(m2·a)-1 P). The results showed that:① in the fourth year of nutrient addition, soil total nitrogen (TN) content was significantly increased. The N:P ratio was significantly increased by N addition, and soil organic carbon (SOC) content was significantly increased by P addition and NP co-addition. In the third and fourth years of nutrient addition, the soil available N:P ratio (AN:AP) was significantly increased by N addition; N addition and NP co-addition significantly increased the content of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) but significantly reduced the soil available C:N ratio. P addition and NP co-addition significantly increased total phosphorus (TP) and soil available phosphorus (AP), whereas it significantly reduced the soil total and available C:P and N:P ratios. ② The interaction between N addition and P addition had a combined effect on NH4+-N, AP, available C:N, and AN:AP ratio of desert grassland. ③ The soil C:N ratio was relatively stable in desert grassland, soil N:P ratio was mainly limited by soil TP content, and the soil available C:P and AN:AP ratios were mainly limited by soil AP content. ④ There were cumulative effects of N and P additions on soil N, SOC, and inorganic nitrogen. N limitation in desert grassland was alleviated by N addition, whereas it was aggravated by P addition and NP co-addition. The variation coefficients of soil available stoichiometric characteristics were higher than that of soil total stoichiometric characteristics. Soil available stoichiometry was more sensitive to N and P addition than soil total stoichiometry in desert grassland, which could better reflect the effects of N and P addition on soil ecological stoichiometry and as a rapid indicator of soil nutrient status in desert grassland.
This paper discusses credit system from its general plotting, flexible study years, flexible charging system, selective courses, elimination system and education control system
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