bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of solution ionic strength on the stabilities of M20 loop conformations in apo E. coli dihydrofolate reductase
Authors: Babu C. Satheesan , Lim Carmay
Published: May 2021

Interactions among ions and their specific interactions with macromolecular solutes are known to play a central role in biomolecular stability. However, similar effects in the conformational stability of protein loops that play functional roles, such as binding ligands, proteins, and DNA/RNA molecules, remain relatively unexplored. A well-characterized enzyme that has such a functional loop is Escherichia coli dihydrofolate reductase (ecDHFR), whose so-called M20 loop has been observed in three ordered conformations in crystal structures. To explore how solution ionic strengths may affect the M20 loop conformation, we proposed a reaction coordinate that could quantitatively describe the loop conformation and used it to classify the loop conformations in representative ecDHFR x-ray structures crystallized in varying ionic strengths. The Protein Data Bank survey indicates that at ionic strengths (I) below the intracellular ion concentration-derived ionic strength in E. coli (I ≤ 0.237M), the ecDHFR M20 loop tends to adopt open/closed conformations, and rarely an occluded loop state, but when I is >0.237M, the loop tends to adopt closed/occluded conformations. Distance-dependent electrostatic potentials around the most mobile M20 loop region from molecular dynamics simulations of ecDHFR in equilibrated CaCl2 solutions of varying ionic strengths show that high ionic strengths (I = 0.75/1.5M) can preferentially stabilize the loop in closed/occluded conformations. These results nicely correlate with conformations derived from ecDHFR structures crystallized in varying ionic strengths. Altogether, our results suggest caution in linking M20 loop conformations derived from crystal structures solved at ionic strengths beyond that tolerated by E. coli to the ecDHFR function.
Subluminal electrostatic noise in isotropic space plasmas. General formulas and nonrelativistic thermal limit
Authors: Schlickeiser R. , Martinović M. M. , Yoon P. H.
Published: May 2021

The properties of the collective subluminal electrostatic fluctuations in isotropic plasmas are investigated using the covariant kinetic theory of linear fluctuations based on the correct momentum–velocity relation. The covariant theory correctly accounts for the differences in subluminal and superluminal fluctuations in contrast to the non-covariant theory. The general formalism developed here is valid in unmagnetized plasmas and in magnetized plasmas for wavevectors of electrostatic waves parallel to the direction of the uniform magnetic field. Of particular interest are potential differences between the covariant and the non-covariant approach and the consequences of these differences in modifying observational predictions. For thermal particle distributions of protons and electrons with nonrelativistic equal temperatures, the covariant and non-covariant theories yield exactly the same dispersion function and relation for weakly damped electrostatic waves. Also, the quasi-equilibrium wavenumber spectrum of collective thermal electrostatic noise agrees in both theories apart from the important wavenumber restriction |k|>kc=ωp,e/c. While the non-covariant analysis also yields eigenmode fluctuations at small wavenumbers with superluminal phase speeds, the correct covariant analysis indicates that subluminal electrostatic fluctuations are only generated at wavenumbers |k|>kc by spontaneous emission of the plasma particles. As a consequence, the nonrelativistic thermal electrostatic noise wavenumber spectrum is limited to the wavenumber range ωp,e≤|k|≤kmax. Within a linear fluctuation theory, superluminal electrostatic noise cannot be generated.
Analysis of increase in forward transconductance to determine the critical point of polarization at ferroelectric 1T1C memory
Authors: Chang Kai-Chun , Chen Po-Hsun , Chang Ting-Chang , Yeh Chien-Hung , Lin Yun-Hsuan , Chang Yen-Cheng , Chen Wen-Chung , Tan Yung-Fang , Wu Chung-Wei , Sze Simon
Published: May 2021

This paper studies a composite device composed of ferroelectric random access memory (FeRAM) and metal-oxide-semiconductor field effect transistor. The relationship between the hysteresis characteristics and VG is reported, and the on/off ratios under different writing voltages are presented. The gm–VG curve of the forward and reverse sweeping shows that under forward sweep a very clear instability appears while voltage increases. The reasons for this can be explained according to the voltage divider rule, the ID formula, and gm formula of transistors, which show that there is polarization of the ferroelectric material. Accordingly, a method is proposed to determine the critical point of the ferroelectric capacitor polarization in this 1T1C structure, which is advantageous because it identifies the appropriate reading voltage necessary for an effective program state of the 1T1C device. This method was shown in three 1T1C and three FeRAMs devices with different ferroelectric areas. Finally, this method was verified by the P–V loop of FeRAMs.
Experimental investigation on optimal plasma generation in inductively coupled plasma
Authors: Hong Young-Hun , Kim Ju-Ho , Kim Tae-Woo , Lee Ho-Won , Lee Moo-Young , Chung Chin-Wook
Published: May 2021

Total energy loss per ion–electron pair lost (εT) is investigated to optimize the plasma generation at various RF powers and gas pressures in an argon inductively coupled plasma (ICP). The ion densities and electron temperatures are measured to obtain εT at the plasma–sheath edge. At a fixed RF power, the obtained εT has a minimum at a certain electron temperature, and at this condition, an optimal plasma generation is achieved according to a global model. Since the electron temperature is a function of the gas pressure, at that certain gas pressure the energy loss in the plasma is minimized and plasma is generated most efficiently. Interestingly, the electron temperature at which εT becomes the minimum decreases as the RF power increases. This is explained by multistep ionization and the electron density dependence of the density of the excited states. Measured εT is compared with the calculated result from the global model that includes multistep ionization, and these are consistent with each other.
Understanding intermolecular interactions of large systems in ground state and excited state by using density functional based tight binding methods
Authors: Xu Yuan , Friedman Ran , Wu Wei , Su Peifeng
Published: May 2021

A novel energy decomposition analysis scheme, named DFTB-EDA, is proposed based on the density functional based tight-binding method (DFTB/TD-DFTB), which is a semi-empirical quantum mechanical method based on Kohn–Sham-DFT for large-scale calculations. In DFTB-EDA, the total interaction energy is divided into three terms: frozen density, polarization, and dispersion. Owing to the small cost of DFTB/TD-DFTB, DFTB-EDA is capable of analyzing intermolecular interactions in large molecular systems containing several thousand atoms with high computational efficiency. It can be used not only for ground states but also for excited states. Test calculations, involving the S66 and L7 databases, several large molecules, and non-covalent bonding complexes in their lowest excited states, demonstrate the efficiency, usefulness, and capabilities of DFTB-EDA. Finally, the limits of DFTB-EDA are pointed out.
Quantum transport in a one-dimensional flux rhombic lattice
Authors: Muraev P.S. , Kolovsky A.R.
Published: May 2021

We analyse stationary current of the bosonic particles in a flux rhombic lattice connecting two particle reservoirs. For vanishing interparticle interactions the current is shown to monotonically decrease as the flux is increased and become strictly zero for the Peierls phase equal to π. Nonzero interactions modify this dependence and for moderate interaction strength the current is found to be independent of the flux value.
Iterative quantum phase estimation on an IBM quantum processor
Authors: Zhuravlev N.A. , Beterov I.I.
Published: May 2021

An elementary algorithm of quantum phase estimation based on the modified Kitaev algorithm is implemented on two qubits of an IBM quantum processor. This algorithm includes adiabatic preparation of the initial state, controlled phase shift with allowance for the results of previous measurements of qubit states, and single measurement of the qubit quantum state in order to obtain each significant bit of the measured phase. Classical error correction is applied to determine the correct sequence of bits, which makes it possible to eliminate the influence of limited accuracy of two-qubit gates.
CXCR4/CXCL12-mediated entrapment of axons at the injury site compromises optic nerve regeneration
Authors: Hilla Alexander M. , Baehr Annemarie , Leibinger Marco , Andreadaki Anastasia , Fischer Dietmar
Published: May 2021

Significance

Retinal ganglion cell (RGC) axons in the optic nerve convey visual information from the eye to the brain. Injury causes permanent functional loss as axons cannot regenerate. This failure is generally attributed to an insufficient intrinsic regenerative capacity, the extrinsic inhibitory environment, and RGC death. Here, we show that a chemoattractive CXCL12/CXCR4-dependent mechanism entraps growth-stimulated axons at the lesion site, thereby limiting axon extension in the nerve. Accordingly, specific depletion of either CXCR4 or CXCL12 in growth-stimulated RGCs releases entrapped axons and markedly enhances nerve regeneration at long distances. Thus, active CXCL12/CXCR4-mediated attraction to the injury site represents a mechanism preventing central nervous system (CNS) axon regeneration. Moreover, treatments targeting CXCL12/CXCR4 signaling may be promising approaches to improve CNS repair.
DNAM-1 regulates Foxp3 expression in regulatory T cells by interfering with TIGIT under inflammatory conditions
Authors: Sato Kazuki , Yamashita-Kanemaru Yumi , Abe Fumie , Murata Rikito , Nakamura-Shinya Yuho , Kanemaru Kazumasa , Muratani Masafumi , Veillette André , Goto Motohito , Ito Mamoru , Shibuya Akira , Shibuya Kazuko
Published: May 2021

Significance

Immune tolerance is essential to prevent autoimmune responses, but it often needs to be limited for proper immune response. Regulatory T (Treg) cells play a crucial role in immune tolerance; however, their immune-suppressive function is restricted under inflammatory conditions. Here, we show that the activated immune receptor DNAM-1 limits Treg cell function regardless of DNAM-1–mediated intracellular signaling. We found that DNAM-1 competes with T cell immunoreceptor with Ig and ITIM domains (TIGIT) in binding to a common ligand. DNAM-1 deficiency enhances TIGIT signaling, thus resulting in the Treg cell function’s maintenance under inflammatory conditions. These results suggest that the DNAM-1 and TIGIT balance orchestrate Treg cell function for optimal immune reaction.
Chromatin remodeler
Arid1a
regulates subplate neuron identity and wiring of cortical connectivity
Authors: Doyle Daniel Z. , Lam Mandy M. , Qalieh Adel , Qalieh Yaman , Sorel Alice , Funk Owen H. , Kwan Kenneth Y.
Published: May 2021

Significance

The cognitive, perceptive, and motor capabilities of the mammalian cerebral cortex depend on assembly of circuit connectivity during development. Subplate neurons, strategically located at the junction of gray and white matter, orchestrate the wiring of cortical circuits. Using a genetic approach to study gene necessity and sufficiency in subplate neurons, we uncover an essential role for chromatin remodeler
Arid1a
in subplate neuron gene expression and axon guidance functions. Cortical deletion of
Arid1a
disrupts subplate-dependent formation of corpus callosum, targeting of thalamocortical axons, and development of sensory maps. Together, our study identifies
Arid1a
as a central regulator of subplate-dependent axon pathfinding, establishes subplate function as essential to callosum development, and highlights noncell-autonomous mechanisms in neural circuit formation and disorders thereof.
Norwegian teacher students’ conceptions of grammar
Authors: Nygård Mari , Brøseth Heidi
Published: May 2021

This paper explores the conceptions of grammar of first-year teacher students (N = 235) in Norway. A conventional content analysis is used to analyse the answers from the first part of a survey exploring the teacher students’ views of grammar through the following questions: Q1. How would you define the term grammar? Q2. Do you think grammar is an important part of Norwegian as a school subject? Q3. Do you feel confident in grammar? The second part of the survey is a grammar knowledge test. The results show that most students define grammar as writing correctly. Many answers also refer to language structure. Among the less frequent definitions are: theoretical knowledge of language structure, precise communication, text, and constituent analysis. Nearly all students report that they consider grammar important. Moreover, most consider their own grammar competence to be relatively good. However, there is a discrepancy between this self-evaluation and the results from the knowledge test, which are quite poor. Our study contributes to the body of research on teacher students’ conception of grammar, which, in a Norwegian context, has been unexplored. We discuss our findings in the light of national and international literature, and we propose plausible contributing factors. We also reflect upon possible consequences for teacher education.
Per1/Per2–Igf2 axis–mediated circadian regulation of myogenic differentiation
Authors: Katoku-Kikyo Nobuko , Paatela Ellen , Houtz Daniel L. , Lee Britney , Munson Dane , Wang Xuerui , Hussein Mohammed , Bhatia Jasmeet , Lim Seunghyun , Yuan Ce , Asakura Yoko , Asakura Atsushi , Kikyo Nobuaki
Published: May 2021

Circadian rhythms regulate cell proliferation and differentiation, but circadian control of tissue regeneration remains elusive at the molecular level. Here, we show that proper myoblast differentiation and muscle regeneration are regulated by the circadian master regulators Per1 and Per2. Depletion of Per1 or Per2 suppressed myoblast differentiation in vitro and muscle regeneration in vivo, demonstrating their nonredundant functions. Both Per1 and Per2 were required for the activation of Igf2, an autocrine promoter of myoblast differentiation, accompanied by Per-dependent recruitment of RNA polymerase II, dynamic histone modifications at the Igf2 promoter and enhancer, and the promoter–enhancer interaction. This circadian epigenetic priming created a preferred time window for initiating myoblast differentiation. Consistently, muscle regeneration was faster if initiated at night, when Per1, Per2, and Igf2 were highly expressed compared with morning. This study reveals the circadian timing as a significant factor for effective muscle cell differentiation and regeneration.
Digital and analog functionality in monolayer AlOx-based memristors with various oxidizer sources
Authors: Zhan Xuepeng , Zhao Guoqing , Yu Xiaolin , Chen Bo , Chen Jiezhi
Published: May 2021

Memristors with the outstanding advantages are beneficial for neuromorphic computing and next-generation storage. Realizing various resistive switching behaviors in monolayer memristors is essential for understanding the device physics and fabricating fully memristive devices. In this paper, a simple and feasible method was proposed to achieve the digital and analog resistive switching in Cu/AlOx/Ag memristors by using ozone and water precursors in atomic layer deposition. According to the characterization results of surface topography, Raman spectrum and electrical measurement, the transition between the abrupt and gradual resistive switching was ascribed to the migration and diffusion of active electrode metal ions in the sparser, rougher and more amorphous AlOx dielectric films. The key features of biological synapses including long-term potentiation/depression, paired-pulse facilitation and learning-experience behaviors were emulated in the analog monolayer memristors. This study makes an important step towards the development of the sophisticated, multi-functional, and large-scale integrated neuromorphic devices and systems.
Shielded high dose rate ocular brachytherapy using Yb-169
Authors: Dupere Justine M , Munro John J , Medich David C
Published: May 2021

Purpose. We propose an approach for treating ocular melanoma using a new type of brachytherapy treatment device. This device couples Yb-169, a middle-energy high dose rate (HDR) brachytherapy source, with a gold shielded ring applicator to better conform radiation exposures to the tumor. In this study, we computationally test the dosimetric output of our proposed shielded ring applicator design using MCNP6 and validate it against an I-125 COMS plaque. Methods. The proposed Yb-169 ring applicator consists of an assembly of discrete sources delivered into an applicator with a conical collimated opening; this opening is tangent to the outside of the source tube. Using MCNP6, we simulated the dosimetric output of a ring of Yb-169 pellets placed within the collimator at various conical diameters and angles to demonstrate the dosimetric distribution for various prescription dose depths and target sizes using static intensity modulation. Results. Using various angles of collimation, the prescription dose was delivered to target apex depths of 3.5–8.0 mm into the eye covering target sizes ranging from 10 to 15 mm in diameter. This proposed device reduced the maximum absorbed dose to critical structures relative to I-125 by 5.2% to the posterior lens, 9.3% to the iris, 13.8% to the optic nerve, and 1.3% to the sclera. Conclusions. This proposed eye plaque design provides a more conformal dose distribution to the ocular tumor while minimizes dose to healthy ocular structures. In addition, the use of a middle-energy HDR brachytherapy source allows the use of a remote afterloader to expose the tumor after the plaque is sutured in place. This system is inherently safer and eliminates dose to the surgeon’s hands.
1-bit reconfigurable transmitarray with low loss and wide bandwidth
Authors: Gao Wen Hua , Chen Mao , Cheng Qiang , Shao Rui Wen , Liang Jing Cheng , Gao Yuan , Cui Tie Jun
Published: May 2021

We present a novel X-band 1-bit reconfigurable transmitarray with excellent polarization conversion. The basic element consists of two layers of metal patterns connected by a metal through-hole and feed structures. The top layer is used to realize a 1-bit phase response by controlling the states of two PIN diodes; the bottom layer is composed of a rectangular patch with a U-slot to realize conversion from linear polarization to cross polarization. The agreement between simulation and measurement results indicates that when the diode states are switched in turn, this unit achieves the phase difference of cross-polarized transmitted waves within 180° ± 15° and high transmittance in a broad band. The scattering patterns demonstrate that beam splitting or multi-beam generation can be achieved by controlling the different coding sequences of each column unit. The element offers low transmission loss, wide bandwidth of 1-bit phase control, and small thickness for easy integration. Thereby, it has numerous potential applications in radar and wireless communications.
Underestimates of methane from intensively raised animals could undermine goals of sustainable development
Authors: Hayek Matthew N , Miller Scot M
Published: May 2021

Greenhouse gas emissions from meat and dairy production are often highly uncertain; these emissions are typically estimated using inventory-based, ‘bottom-up’ models, which contain uncertainties that are difficult to quantify. Modeled emissions estimates can be corroborated using atmospheric measurements—taken above and downwind of animal production regions—to produce ‘top-down’ emissions estimates. Top-down and bottom-up estimates of animal methane show good agreement when considering global emissions. However, in the US, where animal production is predominantly highly intensified with confined feeding operations, animal methane emissions may be 39%–90% higher than bottom-up models predict (expressed as mean differences across studies). Animal emissions may grow in the future as meat and dairy demand increases in developing countries. We examine East and Southeast Asia as a test case, where emissions from increased meat and dairy production are expected to be offset by improved efficiency from intensive methods. We adjust the share of direct emissions projected to come from intensive systems by the intensities derived from US top-down estimates. We find that region-wide emissions from meat and milk production could reach 1.52 (1.41–1.62) GtCO2eq by 2050, an amount 21% (13%–29%) higher than previously predicted. Therefore, intensification may not be as effective in mitigating emissions in developing countries as is commonly assumed.
An Overview of Energy Efficiency and Management; a Case Study of Rural Electrification Agency Building
Authors: Asogwa J C , Fulani F B , Okafor I F
Published: May 2021

Sustainable energy management essentially plays a critical role in the socio-economic activities of man and in the overall productive processes of a nation; consequently, efficient energy utilization and robust management are key parameters that drive energy sustainability. Energy efficiency in this context can be viewed as a function of technological advancement, owing to the fact that what are regarded as efficient products in the seventies and thereafter have in the contemporary time been replaced by the modern efficient ones. In the industries, obsolete equipment is giving way to more efficient and automated ones. Architects too have improved considerably in the design of energy efficient buildings, while in the transport sector, energy efficient automobiles that are eco-friendly are gradually emerging. The work had in general terms discussed energy efficiency and management programmes, and for emphasis, analyzes the results which were obtained during the Walk-through and Diagnostic Energy Audit carried out in the offices of Rural Electrification Agency Building located in FCT. The audit work as presented in this study serves as a measure for exposing all the areas of energy wastages and feasible conservation opportunities in the building complex. Energy Audit Devices deployed in the power sources of the building with behavioral and bioclimatic information as collated produced a reliable data that were used in this study and thus gave broad knowledge of energy efficiency and management measures for achieving sustainability in our national economy.
Biogas Production and Storage from Pig Dung Co-Digested With Pineapple Peel
Authors: Ofomatah A C , Ugwu K E , Ani J U
Published: May 2021

Biomethanation potentials of pig dung co-digested with pineapple peels were investigated. Various blends of pig dung with pineapple peels were charged respectively into 50 kg prototype digesters labeled A to C. Digesters D and E were charged with only pineapple peels and pig dung respectively. Proximate and physico-chemical analyses were determined on the slurry using conventional methods. The wastes were subjected to anaerobic digestion for 35 days at mesophilic temperature range of 25 to 37°C. Relative humidity, ambient temperature, pH, slurry temperature and volume of gas were monitored and recorded on daily basis. Biogas yield increased progressively with higher pig dung blend. Onset of gas flammability was observed on the 5th day for blends of pig dung and pineapple peels, as well as for pineapple peels alone while for pig dung alone, it was observed on the 6th day. This was as a result of lower nitrogen contents of pineapple peels blends compared with that of pig dungs alone, a factor which favours early onset of flammability. Biogas generated from the mixture ranged from 65- 71% CH4, 28 -34% CO2, and traces of hydrogen sulphide and carbon (II) oxide. The biogas was subsequently stored in a gas cylinder using modified pressure system. This study is aimed at converting wastes such as pig dung and pineapple peels to useful energy and storing the gas produced in cylinders for easy accessibility.
Multi-Power Source and Cloud-Backup Enabled Security Framework for Surveillance in Nigeria
Authors: Adebisi J A , Abdulsalam K A , Adams I. O.
Published: May 2021

In Nigeria, power is one of the major problems and this deters the reliability and effectiveness of a video surveillance system as the case may be. Also, as criminal organizations tend to destroy every physical storage after an operation, providing a suitable backup to the cloud is a viable solution to serve as a failsafe plan in case of hardware eventualities. This work focuses on the design and construction of a real-time power and data backup surveillance system for security of lives and properties. Construction of a sufficient power bank backup system was developed in real time with average power outage duration in Nigeria considered. Lithium ion batteries with a cascade connection was used to provide alternate power to the system in a situation of power outage. An Arduino microcontroller controlling relay modules was used to ensure optimum battery life and efficiency and an IP camera was used for surveillance as well as cloud storage. This research was implemented and evaluated to measure the efficiency of the system. The results show that the entire system has the capacity to switch between the direct power source and the alternative power source, it could last for 100- 156hours after full charge in absence of power supply. The data backup was stored to a secured cloud and could only be accessed by authorized users when such is required.
Assessment of wind energy potential of Bauchi in North-East, Nigeria
Authors: Igwebuike M N , Ezeugwu C I
Published: May 2021

Twenty year (1995-2014) monthly mean wind speed and monthly mean wind direction data of Bauchi location were obtained from the Nigeria Meteorological Agency (NIMET) Lagos for the purpose of this study. The data was measured at 3 m height. In order to evaluate wind characteristics, statistical models such as Weibull and Rayleigh distribution were employed in the assessment of wind energy potential. It was observed that Weibull distribution suited the wind speed data more than Rayleigh. Wind rose plot of the monthly wind direction was plotted to determine the best possible direction to mount wind turbine in Bauchi station. Wind characteristics obtained at 3 m height were extrapolated for higher altitudes.
Inspection of Residential Electrical Installations in Bayelsa State: A Review
Authors: Yabefa E. T. , Ainah P. K.
Published: May 2021

The importance of initial verification and the need for periodic inspection and testing of the electrical installation of residential buildings cannot be overemphasized. Fire outbreak in residential buildings is very frequent in Bayelsa State and mostly attributed to electrical fault. The initial verification and periodic inspection and testing are unavoidable electrical procedures for the continuous safe use of any electrical installation. In this paper, a safe working procedure for periodic inspection is presented. The use of the schedule of circuit details, and the electrical danger notification (EDN) form is also presented. The periodic inspection and testing of the electrical installation in residential premises would definitely minimise the frequently witnessed electrical fire in residential buildings in Bayelsa State, and consequently guaranty the safety of both the building and the occupants of the property.
Adoption of appropriate technology for building construction in the tropics; a case of Nigeria
Authors: Nwalusi Dickson M. , Okeke Francis O.
Published: May 2021

Construction technology from the West has played a vital role in building construction in the Tropics. Due to the level of organization, capital and personnel, some cities within Africa can absorb the latest technology faster and better than other cities; thus, their construction development projects using the western borrowed and learned technology has been verbatim and most times, excessively done. This trend, which cuts across many regions of tropical Nigeria leads to the neglect of folk wisdom. Local construction wisdom is usually substituted for new technology without the geography of the area being considered. In 1996, the economic crisis caused the construction business to come to a halt. The cost of oversea technology significantly increased due to the baht flotation policy. Several manufacturers and contractors went bankrupt at that time, including owners of small property in remote parts. While it seems that construction problems from the past are being alleviated, some signs of financial crisis are still evident in recent times. To prevent such future reoccurrence, the study focuses on appropriate construction technology to create social resilience and promote sustainable development. Utilizing literature review research methodology, the concept of appropriate technology is examined, highlighting the appropriate construction technology for the industry in Nigeria’s tropical environment. Photographs of existing building of historic and contemporary architecture were collected and used as a basis for analysis of building construction technology. Benefits and hindrance of appropriate technology are discussed and the research concludes that the only way to achieve economic, social and environmental justice and sustainability is by the adoption of this appropriate technology.
Centralized Electricity Grid and the Rural Economy of Nigeria
Authors: Uzoma C , Atama C , Okpara K , Igwe I , Nnaji M , Adagba C , Onyekaozuru E
Published: May 2021

Electricity is necessary for economic development and no doubt, the best way to ensure adequate supply is through the grid. Nigeria operates a centralized grid system and little is known about how the centralized grid system impacts on the rural economy. This paper examines the impact of the centralized electricity grid on rural electrification and rural economy of Nigeria. Questionnaires were employed to generate data, from 894 respondents in three senatorial districts, in Imo State. Data analysis was conducted using descriptive and inferential (X2 -Chi square) statistics. Result shows that the electricity situation in rural areas is abysmal. Consequently, rural living standard is very low, due to lack of income opportunities. It is concluded that given Nigeria’s large geographical size, the centralized grid rural electrification is fundamentally inadequate. A decentralized electricity structure with emphasis on mini-grids and a priority on localized generation is recommended.
Development of Carbon Fibre Reinforced Natural Rubber Composite for Vibration Isolation
Authors: Eyo-Honesty R. E. , Egbe  , Evudiovo P.
Published: May 2021

This study is based on readily available materials within the locality. The extraction of carbon fibre from periwinkle shell is to reduce the high cost of processing carbon fibre from petroleum pitch and to serve as reinforcement to the natural rubber resin. The fibre was activated using potassium hydroxide (KOH) followed by characterization through XRF, tensile test, hardness and impact test. On forming the composite, the reinforced material was calculated on percentages: 10%, 20% and 30% and added differently to 220grams of natural rubber resin. The samples were then prepared for various tests analysis based on ISO and ASTM standard,(ISO 527 for tensile test, ISO 179 for impact test and ASTM D2240 for hardness test) to determine the composite strength in comparison with the natural rubber for vibration isolation. The basis for this comparison is because natural rubber is widely used as a vibration isolator. The result shows an increased in tensile strength of the composite to 0.20 mega Pascal as against 0.09 mega Pascal of natural rubber resin, good strain rate for improved isolator life and high resistance to thermal expansion
A Grid Tied Short-Through Proof Solar PV Inverter
Authors: Agu M U , Ejiogu E C , Nnadi D B N , Eya C U
Published: May 2021

In this paper, a new grid tied short-through proof solar photovoltaic (PV) inverter that is short-through proof is presented. Detailed presentation of this new solar inverter is preceded by a brief explanation of the generalized solar PV inverter, its types and some representative grid tied solar inverters (mainly micro-inverters) that are currently trending in the solar PV power conversion industry. The merits of each of these briefly explained solar inverter types and power circuits are emphasized. The new grid tied galvanic isolated solar inverter power circuit is then explained in detailed, analyzed and the steady state time varying circuit voltages and currents given. In addition to being short through proof, the new grid tied solar inverter is scalable from solar PV micro-inverter to solar PV central inverter in output power capability unlike the conventional grid-connected single phase inverters.
Spent bio-slurry from “Adani” rice husk mixed with graded levels of cow dung in bio-gasification: Heavy metals identification and potentials
Authors: Ofomatah AC , Uzodinma EO , Ojike O
Published: May 2021

Heavy metals identification and potentials of spent bio-slurry from “Adani” powdered rice husk (PRH) mixed with graded levels of cow dung (CD) in bio-gasification process was investigated. The waste complements include; 90:10, 80:20, 70:30, 60:40 and 50:50 PRH: CD, respectively. The PRH and CD separately served as control. Bio-wastes validity for the anaerobic digestion (AD) process based on physico-chemical properties and calorific values were determined using standard laboratory methods. All the wastes were gasified at ambient conditions using biogas plants of similar volume (48 L) for 30 days. The spent bio-slurry was evaluated for heavy metals (Ni, Cr, Cu, Zn, Mn, Pb, Fe and Ag) and macro elements (Ca, Mg and K) using atomic absorption spectrophotometer. Nutrient contents of undigested wastes showed reliability for the bio-gasification and the waste systems yielded total gas volumes of123, 127, 125, 141, 127, 246 and 291 liters for 90:10; 80:20; 70:30; 60:40 and 50:50 PRH: CD, PRH and CD, respectively. Onset of flammable gas ignition by digester systems were recorded as 15, 15, 11, 9, 6, 8 and 4 days, for the composite and single wastes, respectively. Concentrations of the heavy metals in the spent bio-slurry composite (90:10, 80:20, 70:30, 60:40 and 50:50 PRH: CD) ranged from 4.28- 21.37(Ni); 0.00-4.86 (Cr); 0.00-2.37 (Ag); 0.00-2.70(Cu); 0.00-10.42(Pb); 0.00- 9.46(Mn), 61.14-1,589.65(Fe)and 1.80-17.32 (Zn) ppm/g of sample, respectively. Concentrations for Ca range from 111.12-333.36; K: 9.67-35.45; Mg: 127.14-238.52 ppm/g of sample. Overall results showed that partially decayed ‘Adani’ powdered rice husk could generate biogas energy in single and co-digested forms for cooking and lighting, among other benefits. Secondly, the co-digested spent slurries contained low amounts of the heavy trace metals identified and have great potentials for application to organic farming and horticultural practices.
The Challenges of Estimated Billing on Electricity Consumers in Nigeria: A Review
Authors: Soyemi A O , Samuel I A , Ayobami A A Olajube , Akinmeji A
Published: May 2021

Despite Government efforts, over 4.6 million Nigerians are on the estimated billing system. Nigeria has one of the highest aggregate technical, commercial and collection losses at 43.65%, which has been attributed to low investments in distribution networks exacerbated by the slow progress of metering of customers which has posed a protracted liquidity challenge to the industry. There is a need to reduce these losses; hence this paper examined the Nigerian electricity billing system through meta-analysis of literature, with a focus on estimated billing, the metering situation, and its challenges in Nigeria. Finally, solutions such as the implementation of a cost reflective tariff scheme are proffered through recommendations to distribution companies and the Federal Government of Nigeria.
Energy Efficiency and Conservation
Authors: Olughu O U
Published: May 2021

Energy efficiency and energy conservation (EEAEC) is the forerunner to an ideal energy solution for sustainable development. Both EE and EC join forces to achieve and maintain optimum energy procurement and utilization in any household or organization. They help also to minimize energy costs, wastes as well as environmental ill-effects without affecting quality of work done in production process. Energy efficiency (EE) means saving energy while keeping the same level of service. It is the ability to capitalize on new technologies and equipment to do same work with less energy. On the other hand energy conservation (EC) is achieved when you adopt better ways of doing things using the same amount of available energy to perform more useful work. EC reduces the need for non-renewable sources of energy. The spin-offs can result in increased environmental quality, national and personal security together with higher cost saving which places EC at the top of the sustainable energy portfolio hierarchy in ranking. This paper therefore should be seen as stimulus to ginger us to adopt every acclaimed energy thrift procedures uniquely in our daily activities, anthropogenic lifestyles and processes in industries. The paper has tried to examine and demonstrate the technical differences between EE and EC, thus enabling us to develop an energy audit checklist relevant for home, commercial and industrial applications.
Solar electricity generation using a photovoltaic-thermoelectric system operating in Nigeria climate
Authors: Maduabuchi C , Eke M
Published: May 2021

This paper presents the performance evaluation of a hybrid photovoltaic-thermoelectric (PV-TE) system operating under practical conditions in Nigeria climate. The thermoelectric generator (TEG) is directly attached to the back plate of the PV cell and is used to regulate the cell temperature while increasing its overall efficiency. A three-dimensional finite element model is developed in ANSYS 2020 R1 commercial software and is utilised in studying the temperature and electric distribution of the hybrid system operating under practical conditions. Temperature dependent material properties are also considered. The simulation is carried out for 24 h to encompass both day and night operation of the hybrid system. Results indicate that power output obtained from the hybrid PV-TE set up is higher than that harvested from the stand-alone PV system. Furthermore, the TEG acts as a heat sink by converting the waste infrared radiation from the PV to electricity. Hence, the incorporation of TEGs to PV systems is highly encouraged since this will result in better system performance at relatively low cost. The results obtained from this study will provide a reference for the design of hybrid photovoltaic-thermoelectric systems operating in Nigeria.
Electricity and Biofuel Production from Biomass in Nigeria: Prospects, Challenges and Way Forward
Authors: Ezealigo U S , Otoijamun I , Onwualu A P
Published: May 2021

Nigeria currently produces less energy required for uninterrupted electricity supply. This situation has led to an energy crisis that is adversely affecting every sector of the economy. An exploration of energy contributions from different sources could help address the energy crisis in Nigeria. This paper aims at promoting the commercial availability of electricity from biomass in Nigeria. The biomass potentials identified include conventional crops, agricultural residues, tertiary residues; forest residues; energy crops; grasses and aquatic weeds including algae. Conversion of biomass to bioenergy can be achieved through anaerobic digestion, gasification, pyrolysis or esterification. Although the prospects are bright, challenges facing bioenergy in Nigeria, include inadequate information on feedstock; uncomprehensive research and development capacity; poor policy formulation and implementation; poor regulatory framework, poor investment climate and poor access to technology. An integrated approach is recommended to include the establishment of Nigerian Biofuel Corporation under a Public-Private Partnership (PPP) arrangement and a Nigerian Network on Bioenergy.
Assessing the Technical Offshore Wind Energy Potential in Lagos, Nigeria
Authors: Attah A R , Abubakar J , Badejo J
Published: May 2021

Looking at the current state of things globally and the greenhouse effect renewable energy sources are no longer a matter of choice. The population of Lagos coupled with the perpetually erratic power supply makes renewable energy the new and sure way to go especially as an alternative supply of electricity. The nation as a whole has a peak generation of 5300MW on average which is only about 30% of its actual needs. The use of renewable energy in Nigeria is growing but so is the population this study seeks to ascertain the possibility of using offshore wind energy as an alternative power supply in Lagos Nigeria. The onshore wind energy resource has been fairly explored but its counterpart offshore wind energy has not been explored. This study focuses on the technical assessment of offshore wind resources on the Gulf of Guinea around the Lagos Nigeria region. Having analysed wind data from existing literature and analysed offshore wind farm construction the paper presents a technical layout of the number of turbines per the specified area and the potential output using Aerodyn SCD 8.0/168 as a case study. The results show that the annual energy demand of about 96.36TWh in Lagos can be met with the annual generation of about 191.2TWh for a wind farm at the shore and 200TWh for waters with depth less than 50m.
Addressing Household Cooking Fuel Options in Nigeria
Authors: Nnaji M , Eze A A , Uzoma C C , Nnaji C E
Published: May 2021

Households constitute the most significant sector in energy consumption in Nigeria. A plethora of energy source endowments exists to fulfill this demand. However, addressing the cooking fuels need arises due to issues relating to the economy, health and the environment. This necessitates empirical evidence to effect national efficient choice making and policy to entrench modern energy services. Mixed methods of analysis were employed to assess the economics of household cooking fuel choice, and policy option that would enhance productivity and inform future policy for rapid economic growth and environmental sustainability in Nigeria. Given the study findings from survey, the best alternative household energy for cooking in Nigeria is liquefied petroleum gas (LPG). Unimproved solid fuel use contributing 69.1% and 68.6% clearly dominates the household energy cooking choice over the five year period 2013 and 2018 despite its deleterious effects on the health, productivity and environmental sustainability of the economy. Government support and policy should be used to address the existing energy trilemma of productivity growth, access and security, and environmental sustainability to the economy by effectively utilizing the natural gas (LPG) endowments of Nigeria that was little used of as household cooking fuel choice in the ratio of 2.3% and 14.0% over the same period.
Deployment of energy technologies for sustainable rural agricultural development in Nigeria
Authors: Onah B. N. , Okafor I. F. , Oyigbo D. N. , Nnate K. N.
Published: May 2021

Renewable energy technology deployment is very critical for sustainable rural agricultural development. This study analyses renewable energy technologies for sustainable rural agricultural development in Nigeria. The National Centre for Energy Research and Development, University of Nigeria, Nsukka, has developed viable renewable energy technology devices which include solar powered dryers, solar chicken brooders, solar incubators and solar PV system and biogas production system. This study analyzed the applications of these renewable energy devices and challenges to their deployment for sustainable rural agricultural development. Rural adults mostly involved agricultural practices lack knowledge of modern technologies that could lead to boosting rural agriculture. Thus, exposing them to knowledge of renewable energy technologies, achieving sustainable rural agricultural development is possible.
Performance analysis of the synthetic storm technique rain attenuation prediction model on Nigerian climate
Authors: Tyokighir SS , Mom JM , Igwue GA
Published: May 2021

This study analyzes the performance of the synthetic storm technique (SST) over the Nigerian climate. The location of interest was 9.91°N, 8.88°. Two months rain rate time-series data measured by a rain gauge located inside the University of Jos, Nigeria was utilized for the purpose of this work. The analysis is based on the time-series seasonal variation of rain statistics. Comparison was made between the SST model and measured values at 12.519 GHz for signal downlink from NIGCOMSAT-1R satellite. From results obtained, we observe peak predicted rain attenuation by SST model was 4.06dB with a minimum of 0dB for the month of June while the peak rain attenuation for July was 6.92dB. It can be observed that the SST predicts closely with measured rainfall values. However, disparities exist between the calculated attenuation and the measured values for a few rainfall events. The SST model performance was satisfactory for the period under observation.
Design and Construction of a Semi-batch Pyrolysis Reactor for the Production of Biofuel
Authors: Fombu A H , Ochonogor A E
Published: May 2021

Due to the fast depletion of crude oil wells, increase in greenhouse gas (GHG) emission, energy security challenges, etc. the world through its researchers is in search of sustainable energy sources. Renewable energy sources (RES) have been found to be among the best solutions to the world’s energy insecurity and other challenges, but due to Africa’s poor sustainable energy policies, the positive effect of renewable energy has not been felt in the continent though it has the necessary resources. Biofuel being one of the RES, during its production turns waste into wealth. Pyrolysis is an important method for the production of biofuel, but because of limitations facing the renewable energy technologies (RETs) in Africa (especially the sub-Saharan Africa), constructing a pyrolysis reactor that carries out this process is a challenge to many. A semi-batch reactor was designed (using SOLIDWORKS software) and constructed taking into consideration the process’ kinetics, temperature range (up to 1000 °C) and feedstock (quality and quantity). The system after being constructed was used to produce bio-oil from cashew nut shell, and polystyrene combined with cashew nut shell. They gave pyrolysis liquids of 61.3 % and 64.58 % respectively. This system was designed for laboratory usage; it can be used in homes if scaled to suit home usage.
Condensation inside smooth and inclined smooth tubes at low mass fluxes: A quick review
Authors: Ewim D.R.E. , Okafor I. F.
Published: May 2021

The focus of this research article is to provide a state of the art review on smooth and inclined tubes condensation with particular emphasis on low mass fluxes. The most relevant experimental investigations are explained with a view to identifying the gaps in the literature. Overall, it could be deduced that at low mass fluxes, there needs to be a fundamental understanding between the relationship between difference in temperature and inclination on transfer of heat and pressure drops to enable designers optimize heat exchangers.