Filter options

Publication Date
From
to
Subjects
Journals
Article Types
Countries / Territories
Open Access June 02, 2025

Residual Sets and the Density of Binary Goldbach Representations

Abstract A residual-set framework is introduced for analyzing additive prime conjectures, with particular emphasis on the Strong Goldbach Conjecture (SGC). For each even integer En4, the residual set [...] Read more.
A residual-set framework is introduced for analyzing additive prime conjectures, with particular emphasis on the Strong Goldbach Conjecture (SGC). For each even integer En4, the residual set (En)={Enp p<En,p} is defined, and the universal residual set E=En(En) is constructed. It is shown that E contains infinitely many primes. A nontrivial constructive lower bound is derived, establishing that the number of Goldbach partitions satisfies G(E)2 for all E8, and that the cumulative partition count satisfies ENG(E)N2log4N. An optimized deterministic algorithm is implemented to verify the SGC for even integers up to 16,000 digits. Each computed partition En=p+q is validated using elliptic curve primality testing, and no exceptions are observed. Runtime variability observed in the empirical tests corresponds with known fluctuations in prime density and modular residue distribution. A recursive construction is formulated for generating Goldbach partitions, using residual descent and leveraging properties of the residual sets. The method extends naturally to Lemoine's Conjecture, asserting that every odd integer n7 can be expressed as n=p+2q, where p,q. A corresponding residual formulation is developed, and it is proven that at least two valid partitions exist for all n9. Comparative analysis with the Hardy-Littlewood and Chen estimates is provided to contextualize the cumulative growth rate. The residual-set methodology offers a deterministic, scalable, and structurally grounded approach to additive problems in prime number theory, supported by both theoretical results and large-scale computational evidence.
Figures
PreviousNext
Article
Open Access February 14, 2025

A multi-loci time-series descriptive study on noise levels in a pediatric emergency care department

Abstract Objective: To investigate the status of the acoustic environment of a typical Chinese pediatric emergency care department in a time series and identify the relationship between noise levels and factors such as crowd density and movement. Methods: A descriptive study was designed based on a multi-loci time-series method. We measured three loci under three variable settings: the [...] Read more.
Objective: To investigate the status of the acoustic environment of a typical Chinese pediatric emergency care department in a time series and identify the relationship between noise levels and factors such as crowd density and movement. Methods: A descriptive study was designed based on a multi-loci time-series method. We measured three loci under three variable settings: the decibel value, observation volume, and emergency care volume. Results: The noise levels of the three loci were significantly higher than the internationally recommended levels, exceeding rate reached more than 86.3%. The 24-hour mean map of the three loci showed similar fluctuation patterns, all of which had two peaks at approximately 10:00 AM and 16:00 PM. Conclusions: The daytime and nighttime noise levels were well-fitted by cubic functions with different coefficients. It is suggested that crowd density and movement may play important roles in noise mean fluctuations, which can be optimized to ensure a satisfactory environment in a pediatric emergency care department.
Figures
PreviousNext
Article
Open Access September 26, 2023

Charged Stellar Model with Generalized Chaplygin Equation of State Consistent with Observational Data

Abstract In this paper, we found a new model for a compact star with charged anisotropic matter distribution considering the generalized Chaplygin equation of state. The Einstein-Maxwell field equations have been solved with a particular form of metric potential and electric field intensity. The plots show that physical variables such as radial pressure, energy density, charge density, anisotropy, radial [...] Read more.
In this paper, we found a new model for a compact star with charged anisotropic matter distribution considering the generalized Chaplygin equation of state. The Einstein-Maxwell field equations have been solved with a particular form of metric potential and electric field intensity. The plots show that physical variables such as radial pressure, energy density, charge density, anisotropy, radial speed sound, and the mass are fully well defined and are regular in the star's interior. We obtained models consistent with stellar objects such as GJ 832, LHS 43, SAO 81292, GJ 380, GJ 412, and SAO 62377.
Figures
PreviousNext
Article
Open Access September 26, 2023

Drug-Receptor Interaction of Peptidic HIV-1 Protease: Intermolecular Interaction-III

Abstract Recently, we have studied drug-receptor interaction of the peptidic HIV-1 protease inhibitors based on polar and hydrophobic interactions. We have also studied pharmacokinetics of these inhibitors based on Lipinski’s rule of five and its extended form. After that there was a need to study intermolecular interactions. From literatures, drug-receptor interaction involves hydrogen bonds between [...] Read more.
Recently, we have studied drug-receptor interaction of the peptidic HIV-1 protease inhibitors based on polar and hydrophobic interactions. We have also studied pharmacokinetics of these inhibitors based on Lipinski’s rule of five and its extended form. After that there was a need to study intermolecular interactions. From literatures, drug-receptor interaction involves hydrogen bonds between acceptor and donor sites of drug and its receptor. These donor acceptor sites must be more than four to be dominant. As single intermolecular H-bond is relatively weak and unlikely to support this type of interaction. It is also clear from literature that this interaction contribute to the alignment of reacting species in proper three-dimensional space in such a position that strong and effective polar or hydrophobic or both interaction occurs to form drug-receptor adduct or enzyme inhibitor complex as appropriate. The strength of H-bonds formed between drug and receptor was judged by bond lengths, bond angles and bond orders. As well as, its nature (strong, moderate or weak) and its number, too. Along with H-bonding, we have also studied Van der Walls i.e. non-bonding type interaction. These non-bonding interactions were studied using charge transfer from donor to acceptor and this results transfer of electron flux from donor molecule (drug/receptor) towards acceptor (receptor/ drug). Thus, lowering of energy of the system under investigation will occur. For this resulted interaction energy was also studied that very clearly explain feasibility of interactions. As we know that all above phenomena are molecular properties and do not cover involvement of orbitals. To cover this we have also studied drug-receptor interaction involving molecular orbital. It was HOMO of one reacting molecule (B) that donates electron pair, electron cloud or electron density to LUMO of another reacting molecule (A) that accepts or accommodates this electron pair, electron cloud or electron density. The quantity of the electron flux from HOMO to LUMO was judged by the value of ∆ELH. A lower value of this will support strong and effective drug-receptor interaction. Results of orbital based study have also been found to supports the results as abstracted from interaction energy.
Figures
PreviousNext
Article
Open Access February 09, 2023

Two-Mode Sub harmonic Generator Coupled to Thermal Reservoir

Abstract In this article, our investigation to study squeezing and statistical properties of the light by a two mode sub harmonic generator coupled to thermal reservoir via a single port-mirror. The equation of motion answers are then used to calculate the mean photon number, photon number variance, and quadrature variance for two mode cavity light. However, we have found that the degree of squeezing is [...] Read more.
In this article, our investigation to study squeezing and statistical properties of the light by a two mode sub harmonic generator coupled to thermal reservoir via a single port-mirror. The equation of motion answers are then used to calculate the mean photon number, photon number variance, and quadrature variance for two mode cavity light. However, we have found that the degree of squeezing is indeed affected by the present of thermal light. The mean photon number of the system under consideration increases with increasing n-.
Figures
PreviousNext
Review Article
Open Access November 24, 2022

Relativistic Radial Density Theory (RRDT)

Abstract Starting with Planck scale it is developed the Relativistic Radial Density Theory (RRDT). In this theory, the Planck and gravitational parameters can be described as the functions of the radial mass (energy) density value. This density is maximal at the minimal radius and minimal at the maximal radius. This conclusion is based on the fact that the ratio of Planck mass and Planck length (radius) is constant. These radiuses can be described as the function of the energy conservation constant κ. Using RRDT, it is possible to develop the connections between Planck’s and gravitational parameters as function of the maximal and minimal radial mass (energy) density values. In that sense, the gravitational length, time, energy and temperature can be presented as the function of the Planck length, time, energy and temperature, respectively. This opens possibility to merge of Quantum Field Theory (QFT) and the General Theory of Relativity (GTR) at the quantum scale in gravitational field. The existence of the maximal radial mass (energy) density value at the minimal radius in gravitational field means that no singularity in that field. Further, the existence of the minimal radial mass (energy) density value at the maximal radius in gravitational field means that no infinity in that field. It follows the postulation: the most minimal radius in a gravitational field belongs to the minimal mass (energy). Since the Planck mass is not the minimal mass in space-time, the Planck length/radius is not the minimal length/radius in the space-time. If the calculated minimal (or maximal) radius is the bigger than the related official radius it means that there exists a dark matter in this object. In that sense, the black holes are presenting the state of the matter at the minimal radius where we have the maximal radial mass (energy) density value. Further, the maximal possible radius of the matter is presenting the state with the minimal radial mass (energy) density value. Thus, the maximal and minimal radial mass (energy) density values are constants and conserved items. Now the question is: do motion of the Universe follows the RRDT [...] Read more.
Starting with Planck scale it is developed the Relativistic Radial Density Theory (RRDT). In this theory, the Planck and gravitational parameters can be described as the functions of the radial mass (energy) density value. This density is maximal at the minimal radius and minimal at the maximal radius. This conclusion is based on the fact that the ratio of Planck mass and Planck length (radius) is constant. These radiuses can be described as the function of the energy conservation constant κ. Using RRDT, it is possible to develop the connections between Planck’s and gravitational parameters as function of the maximal and minimal radial mass (energy) density values. In that sense, the gravitational length, time, energy and temperature can be presented as the function of the Planck length, time, energy and temperature, respectively. This opens possibility to merge of Quantum Field Theory (QFT) and the General Theory of Relativity (GTR) at the quantum scale in gravitational field. The existence of the maximal radial mass (energy) density value at the minimal radius in gravitational field means that no singularity in that field. Further, the existence of the minimal radial mass (energy) density value at the maximal radius in gravitational field means that no infinity in that field. It follows the postulation: the most minimal radius in a gravitational field belongs to the minimal mass (energy). Since the Planck mass is not the minimal mass in space-time, the Planck length/radius is not the minimal length/radius in the space-time. If the calculated minimal (or maximal) radius is the bigger than the related official radius it means that there exists a dark matter in this object. In that sense, the black holes are presenting the state of the matter at the minimal radius where we have the maximal radial mass (energy) density value. Further, the maximal possible radius of the matter is presenting the state with the minimal radial mass (energy) density value. Thus, the maximal and minimal radial mass (energy) density values are constants and conserved items. Now the question is: do motion of the Universe follows the RRDT?
Article
Open Access September 20, 2022

High Radio Frequencies interaction of Composite Materials Using Rectangular Waveguide

Abstract The main goal of this paper is studying the composite material behavior under microwave which they used in antennas reflectors. For that, a transmission line method based on X- band WR90 rectangular waveguide is used. The Bi-anisotropic electrical properties are defined as tensors in finite element model. The fibers of the single layer composite are oriented in different directions. The [...] Read more.
The main goal of this paper is studying the composite material behavior under microwave which they used in antennas reflectors. For that, a transmission line method based on X- band WR90 rectangular waveguide is used. The Bi-anisotropic electrical properties are defined as tensors in finite element model. The fibers of the single layer composite are oriented in different directions. The S-parameters (S11 and S12) are calculated using COMSOL Multiyphysics, the S-parameters and currents density behavior show that they very affected by the orientations of the fibers which mean must be considered in any design of RF equipments, more the fibers are parallel with the electrical field more the reflection coefficient get higher.
Figures
Figure 1 (c)
Figure 1 (d)
Figure 5 (b)
Figure 5 (c)
Figure 6 (b)
Figure 6 (c)
PreviousNext
PDF Html Xml
Review Article
Open Access August 21, 2021

Global Analysis of Potential COVID 19 Transmission and Enabling Factors

Abstract Background: Coronavirus disease has caused global turmoil especially causing huge impact on human life all over the world. Current reports states more than 3 million people have lost life and more than 160 million people are known to be suspected with the SARS-CoV-2. Transmission and disease incidence rates are indicators to assess the seriousness of COVID-19 pandemic and studies to understand the factors that aid in this direction are very vital to curb the disease. Methods: The study intends to discover the relationship by performing statistical analysis using correlation and multiple linear regression analysis between the variable’s population density, temperature, relative humidity, and active time of virus and find out the parameters that predict the cases reported per million population in 83 countries. Results: Analysis indicates active time of virus in days is very positively associated with the COVID -19 cases in all the countries r = .604, p < .01. Active time of virus shows strong negative correlation with temperature r = -.930, p [...] Read more.
Background: Coronavirus disease has caused global turmoil especially causing huge impact on human life all over the world. Current reports states more than 3 million people have lost life and more than 160 million people are known to be suspected with the SARS-CoV-2. Transmission and disease incidence rates are indicators to assess the seriousness of COVID-19 pandemic and studies to understand the factors that aid in this direction are very vital to curb the disease. Methods: The study intends to discover the relationship by performing statistical analysis using correlation and multiple linear regression analysis between the variable’s population density, temperature, relative humidity, and active time of virus and find out the parameters that predict the cases reported per million population in 83 countries. Results: Analysis indicates active time of virus in days is very positively associated with the COVID -19 cases in all the countries r = .604, p < .01. Active time of virus shows strong negative correlation with temperature r = -.930, p < .01 revealing that rise in temperature will reduce the virus activity in the population. Together, these variables will account for 36.2% variance in the cases per million population with no significant prediction estimated from any factor. Conclusion: The study outcomes clearly state that population density alone is insufficient to estimate the extent of influence on COVID -19 cases as the number of persons living per sq. km of land is a dynamic quantity tend to fluctuate over time and space due to migration of population. In conjunction to the previous studies reported on the environmental and climatic factors influencing the cases reported, population dynamics does not show much significance on the disease spread and incidence. Contribution: The rise in confirmed cases and the high incidence rate reported in countries can be attributed to the active time of virus life expectancy as there is a positive correlation observed between the COVID-19 cases reported and the virus active time in the examined countries. Also, environment and climatic factors play a role in modulating the infection and transmission rate with less significant influence of population density on the COVID-19.
Figures
PreviousNext
Article
Open Access May 20, 2021

Bioconcentration Factor of Polychlorinated Biphenyls and Its Correlation with UV- and IR-Spectroscopic data: A DFT based Study

Abstract Polychlorinated biphenyls (PCBs) are important class of persist organic pollutants that were used as a component of paints especially in printings, as plastificator of plastics and insulating materials in transformers and capacitors, heat transfer fluids, additives in hydraulic fluids in vacuum and turbine pumps. There is always a need to establish reliable procedures for predicting the [...] Read more.
Polychlorinated biphenyls (PCBs) are important class of persist organic pollutants that were used as a component of paints especially in printings, as plastificator of plastics and insulating materials in transformers and capacitors, heat transfer fluids, additives in hydraulic fluids in vacuum and turbine pumps. There is always a need to establish reliable procedures for predicting the bioconcentration potential of chemicals from the knowledge of their molecular structure, or from readily measurable properties of the substance. Hence, correlation and prediction of biococentration factors (BCFs) based on λmax and vibration frequencies of various bonds viz υ(C-H) and υ(C=C) of biphenyl and its fifty-seven derivatives have been made. For the study, the molecular modeling and geometry optimization of the PCBs have been performed on workspace program of CAChe Pro 5.04 software of Fujitsu using DFT method. UV-visible spectra for each compound were created by electron transition between molecular orbitals as electromagnetic radiation in the visible and ultraviolet (UV-visible) region is absorbed by the molecule. The energies of excited electronic states were computed quantum mechanically. IR spectra of transitions for each compound were created by coordinated motions of the atoms as electromagnetic radiation in the infrared region is absorbed by the molecule. The force necessary to distort the molecule was computed quantum mechanically from its equilibrium geometry and thus frequency of vibrational transitions was predicted. Project Leader Program associated with CAChe has been used for multiple linear regression (MLR) analysis using above spectroscopic data as independent variables and BCFs of PCBs as dependent variables. The reliability of correlation and predicting ability of the MLR equations (models) are judged by R2, R2adj, se, q2L10O and F values. This study reflected clearly that UV and IR spectroscopic data can be used to predict BCFs of a large number of related compounds within limited time without any difficulty.
Figures
PreviousNext
Editorial Article
Open Access June 13, 2021

Properties of Particleboard Made from Recycled Polystyrene and Cocos Nucifera Stem Particles

Abstract The study investigates the use of Recycled Polystyrene (RP) in the production of particleboard. Boards of 6mm thickness with dimension of 350 mm x 350 mm were produced from mixture of Cocos nucifera stem particles and RP. The boards were made at varying mixing ratio of 1:1, 2:1, and 3:1 and board densities of 1000 kg/m3 1100 kg/m3 and 1200 kg/m3. Thickness swelling (TS), Water Absorption (WA), [...] Read more.
The study investigates the use of Recycled Polystyrene (RP) in the production of particleboard. Boards of 6mm thickness with dimension of 350 mm x 350 mm were produced from mixture of Cocos nucifera stem particles and RP. The boards were made at varying mixing ratio of 1:1, 2:1, and 3:1 and board densities of 1000 kg/m3 1100 kg/m3 and 1200 kg/m3. Thickness swelling (TS), Water Absorption (WA), Modulus of Rupture, and Modulus of Elasticity of the boards were evaluated in accordance to ASTM D-1037 standard. Data obtained were subjected to analysis of variance (ANOVA) at 5% probability level. TS and WA decreases as the mixing ratio increases from 1:1 to 3:1 and board density increases from 1000 kg/m3 to 1200 kg/m3. Also, MOR and MOE of boards increase as the board density was increased from 1000 kg/m3 to 1200 kg/m3. However, MOR and MOE of boards initially increase as mixing ratio increases from 1:1 to 2:1 and later decreases with further increase in mixing ratio. The strongest and most dimensionally stable board was produced at board 1200 kg/m3 and mixing ratio 2:1. This study proves that RP is a good substitute for formaldehyde based resin commonly used in particle boards industries.
Figures
PreviousNext
Article
Open Access December 08, 2022

Evaluation of Simulated Petroleum Hydrocarbon on the Physicochemical Properties of Soil

Abstract Petroleum hydrocarbon contamination of soils has become a global concern, which is often caused by anthropogenic activities, posing serious threat to all living beings. The study for evaluation of the variability of crude oil on the physicochemical characteristics of sandy loam soil was conducted at demonstration farm, Rivers state university, Port-Harcourt, Nigeria. The Bonny light crude oil was [...] Read more.
Petroleum hydrocarbon contamination of soils has become a global concern, which is often caused by anthropogenic activities, posing serious threat to all living beings. The study for evaluation of the variability of crude oil on the physicochemical characteristics of sandy loam soil was conducted at demonstration farm, Rivers state university, Port-Harcourt, Nigeria. The Bonny light crude oil was obtained from an oil and gas production company. Uncontaminated soil was mixed with crude oil. Standard procedures were adopted for the laboratory analysis, the parameters analyzed include bulk density, total porosity, pH, available phosphorus (P), Total hydrocarbon content (THC), organic carbon, organic matter, exchangeable cation (Mg, K, Na, Ca), effective cation exchange capacity (ECEC), total exchangeable acidity (TEA), and base saturation were monitored for a period of 21 days. 10 kg of sandy loam soils were mixed with 100, 300, 500, and 700ml of crude oil while no crude oil serves as the control using plastic reactors. The reactor with 700ml of crude oil recorded the highest THC of 1734.33 mg/kg, followed by 500ml with a THC of 1601mg/kg while the control with no contamination recorded the least THC of 534.33mg/kg. However, the values of all concentrations did not meet 5000 mg/kg of Department of Petroleum Resources (2018) intervention value but exceeded the target value of 50 mg/kg. Other parameters followed same trend except porosity which decreased with increase in crude oil volume. There were significant differences at P< 0.05 except for pH, available P, and base saturation. Therefore, this study calls for the utilization of its findings for adoption of remediation on crude oil contaminated soils.
Figures
Figure 2 (c)
Figure 2 (d)
Figure 2 (e)
Figure 2 (f)
Figure 3 (b)
Figure 3 (c)
Figure 3 (d)
Figure 3 (e)
Figure 3 (f)
Figure 3 (g)
Figure 3 (h)
Figure 3 (i)
PreviousNext
PDF Html Xml
Article
Open Access July 22, 2022

DFT-Based Prediction of Anti-Leishmanial Activity of Carboxylates and Their Antimony(III) Complexes Against Five Leishmanial Strains

Abstract Carboxylates and their antimony(III) complexes experimentally scanned earlier for anti-leishmanial activity (IC50) against five leishmanial strains viz., L. major, L. major (Pak), L. tropica, L. mex mex, and L. donovani. These activities have been theoretically predicted by DFT method along with quantitative structure-activity relationship (QSAR) study. Molecular modeling and geometry optimization of the all the eight compounds have been performed on workspace program of CAChe Pro software of Fujitsu by opting B88-PW91 (Becke '88; Perdew & Wang '91) GGA (generalized-gradient approximation) energy functional with DZVP (double-zeta valence polarized ) basis set in DFT (Density Functional Theory). For QSAR, multiple linear regression (MLR) analysis has been performed on Project Leader Program associated with CAChe. The reliability of correlation between experimental activities and predicted activities are r2 = 0.826, r2CV = 0.426 (L. major); r2 = 0.905, r2CV = 0.507 (L. major (Pak)); r2 = 0.980, r2CV = 0.932 (L. tropica); r2 = 0.781, r2CV = 0.580 (L. mex mex) and r2 = 0.634, r2CV = 0.376 (L. donovani [...] Read more.
Carboxylates and their antimony(III) complexes experimentally scanned earlier for anti-leishmanial activity (IC50) against five leishmanial strains viz., L. major, L. major (Pak), L. tropica, L. mex mex, and L. donovani. These activities have been theoretically predicted by DFT method along with quantitative structure-activity relationship (QSAR) study. Molecular modeling and geometry optimization of the all the eight compounds have been performed on workspace program of CAChe Pro software of Fujitsu by opting B88-PW91 (Becke '88; Perdew & Wang '91) GGA (generalized-gradient approximation) energy functional with DZVP (double-zeta valence polarized ) basis set in DFT (Density Functional Theory). For QSAR, multiple linear regression (MLR) analysis has been performed on Project Leader Program associated with CAChe. The reliability of correlation between experimental activities and predicted activities are r2 = 0.826, r2CV = 0.426 (L. major); r2 = 0.905, r2CV = 0.507 (L. major (Pak)); r2 = 0.980, r2CV = 0.932 (L. tropica); r2 = 0.781, r2CV = 0.580 (L. mex mex) and r2 = 0.634, r2CV = 0.376 (L. donovani), and a comparison of the experimental values and the values obtained by theoretical calculations has been presented pictorially that shows close resemblance.
Figures
PreviousNext
Article
Open Access March 25, 2022

Floristic Composition and Structure in the Undergrowth of Agroforests in Neems in the Far North Region (Cameroon)

Abstract This study took place in the Far North region of Cameroon. The general objective was to assess the floristic diversity of the undergrowth of Agrosystems in Azadirachta indica. The data were collected in 100 m long by 20 m wide transects surveyed in plantations of different ages. In total, 5 transects were carried out, ie a total area of 1 ha per site. The sampling bands were established using the compass, decameter, GPS and wires. The experimental set-up used was a 5-repetition split plot. A total of 7689 individuals divided into 9 families, 13 genera and 16 species have been identified. Guiera senegalensis and Piliostigma thonningii are the most common in terms of relative abundance. The analysis of the Family Importance Index (VIF) shows overall that the Combretaceae, and Mimosaceae are the most important in ecological terms. While those of the species show that Guiera senegalensis, Combretum micranthum and Acacia nilotica [...] Read more.
This study took place in the Far North region of Cameroon. The general objective was to assess the floristic diversity of the undergrowth of Agrosystems in Azadirachta indica. The data were collected in 100 m long by 20 m wide transects surveyed in plantations of different ages. In total, 5 transects were carried out, ie a total area of 1 ha per site. The sampling bands were established using the compass, decameter, GPS and wires. The experimental set-up used was a 5-repetition split plot. A total of 7689 individuals divided into 9 families, 13 genera and 16 species have been identified. Guiera senegalensis and Piliostigma thonningii are the most common in terms of relative abundance. The analysis of the Family Importance Index (VIF) shows overall that the Combretaceae, and Mimosaceae are the most important in ecological terms. While those of the species show that Guiera senegalensis, Combretum micranthum and Acacia nilotica finally for the genera, it is Acacia, Guiera and Combretum which contains the most important ecological indices. The overall density of species within the plots varies between 129 and 105 ind / ha. The basal area varies from 2.02 to 3.88 m² / ha. The Importance Value Index (IVI) is of the order of 300 in the different plots. The floristic diversity of the undergrowth of Agrosystems (average ISH> 2) shows homogeneity and an even distribution between the different plots. Plots with similarity indices of less than 50% do not meet floristic affinity while similarity indices are high in plots with floristic affinities greater than or equal to 50%. The diameter structure showed a predominance of young individuals. This information drawn from the conclusion of the present study shows that they constitute an important argumentation of the advantages so that the services of agricultural development should be interested in the conservation and valuation of such an agroforestry system for the protection of the environment against the climate change mitigation and sustainable development of local communities.
Figures
Figure 3 (c)
Figure 3 (d)
PreviousNext
PDF Html Xml
Article
Open Access February 24, 2022

Effects of Carbon Nanotube Structure, Purity, and Alignment on the Heat Conduction Properties of Carbon Films and Fibers

Abstract The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the [...] Read more.
The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the parallel thermal conductance technique was employed to determine the thermal conductivity. The effects of carbon nanotube structure, purity, and alignment on the thermal conductivity of carbon films and fibers were investigated to understand the characteristics of thermal transport in the nanostructured material. The importance of bulk density and cross-sectional area was determined experimentally. The results indicated that the prepared carbon nanotube films and fibers are very efficient at conducting heat. The structure, purity, and alignment of carbon nanotubes play a fundamentally important role in determining the heat conduction properties of carbon films and fibers. Single-walled carbon nanotube films and fibers generally have high thermal conductivity. The presence of non-carbonaceous impurities degrades the thermal performance due to the low degree of bundle contact. The thermal conductivity may present power law dependence with temperature. The specific thermal conductivity decreases with increasing bulk density. At room temperature, a maximum specific thermal conductivity is obtained but Umklapp scattering occurs. The specific thermal conductivity of carbon nanotube fibers is significantly higher than that of carbon nanotube films due to the increased degree of bundle alignment.
Figures
PreviousNext
Article
Open Access September 25, 2021

Root Distribution of Four Tree Species Planted in Living Hedges according to Two Types of Soil and Three Agroforestry Technologies in the Sudano-Sahelian Zone of Cameroon

Abstract In the agroforestry systems of sub-Saharan Africa, the vertical and horizontal distribution of tree root biomass according to the soil profile is still poorly documented. The objective of this study is to verify the root distribution of four species of trees established in living hedges, namely, Commiphora kerstingii,Erythrina sigmoidea,Ficus thonningii and Jatropha curcas according to two types of soil (light soil and heavy soil) and three agroforestry technologies (fallows, wooded parks and plantations). The hedges were mostly monospecific in order to facilitate the identification of the roots. The experimental set-up is an entirely random factorial design with two factors. The evaluation of the distribution of tree roots was carried out using the profile method. To determine the different textural classes, a particle size analysis was undertaken in the laboratory. The results obtained show that the number of roots decreases rapidly after 30 cm of depth. The highest root densities are observed in the first 30 cm. Soil type has a slight effect (p <0.05) on rooting density in the last 30 cm of depth for all root classes, higher densities were obtained in light soil compared to heavy soil. Commiphora kerstingii [...] Read more.
In the agroforestry systems of sub-Saharan Africa, the vertical and horizontal distribution of tree root biomass according to the soil profile is still poorly documented. The objective of this study is to verify the root distribution of four species of trees established in living hedges, namely, Commiphora kerstingii,Erythrina sigmoidea,Ficus thonningii and Jatropha curcas according to two types of soil (light soil and heavy soil) and three agroforestry technologies (fallows, wooded parks and plantations). The hedges were mostly monospecific in order to facilitate the identification of the roots. The experimental set-up is an entirely random factorial design with two factors. The evaluation of the distribution of tree roots was carried out using the profile method. To determine the different textural classes, a particle size analysis was undertaken in the laboratory. The results obtained show that the number of roots decreases rapidly after 30 cm of depth. The highest root densities are observed in the first 30 cm. Soil type has a slight effect (p <0.05) on rooting density in the last 30 cm of depth for all root classes, higher densities were obtained in light soil compared to heavy soil. Commiphora kerstingiistands out significantly by obtaining a higher number of roots than the other species for all classes. Among the technologies, the plantations showed the lowest root density at 0-5 cm and the highest at 55-60 cm. The root density was higher in the fallows. The results show that the root system is mainly concentrated near the stump.
Figures
PreviousNext
Article
Open Access September 16, 2021

Biodiversity Management under Cashew Agro-ecosystems in Central Africa: A case study from Cameroon

Abstract This study aimed to assess the floristic composition, vegetation structure and species associations of Cashew agro-ecosystems in the North region of Cameroon. The data were collected in 100 m x 20 m transect methods. An analysis of the data collected in the field was conducted around the diversity and richness of the flora, but also the structure of Cashew agro-ecosystems. For the analyzes of vegetation structure, tree density, basal area and biovolume were calculated. The inventory included trees with a dbh greater than or equal to 5 cm on an area of ​​1 ha per plot. The experimental device installed is a complete random Fisher block with five repetitions. A total of 7849 individuals in 17 families, 20 genera and 38 species were recorded. Species Important value of vegetation cover indicated that Diospyros mespiliformis, Anogeissus leiocarpus, Annona senegalensis and Terminalia laxiflora are the most represented. Combretaceae are the most ecologically important families. Additionally, the grouping of species into four subdivisions showed that the Shannon diversity index varies from 2.18 ± 0.09 - 3.47 ± 0.17 bits, Pielou index vary from 0.98 ± 0.01 - 0.99 ± 0.01, Simpson's index ranges from 0.70 ± 0.18 - 0.93 ± 0.11, density ranges from 102 ± 1.92 - 128 ± 6.36 indiv/ha, basal area ranges from 2.02 ± 0.31 - 12.68 ± 2.01 m²/ha, biovolume ranges from 11.58 ± 1.29 - 68.03 ± 13.21 m3/ha. The Sörensen similarity index is very high with floristic affinities greater than or equal to 90%. The diameters and heights structure show a predominance of young individuals for the diameter and height classes on all plots. The most represented species associations are legumes (Arachis hypogeae: 40.54%) and native fruit trees (Vitellaria paradoxa [...] Read more.
This study aimed to assess the floristic composition, vegetation structure and species associations of Cashew agro-ecosystems in the North region of Cameroon. The data were collected in 100 m x 20 m transect methods. An analysis of the data collected in the field was conducted around the diversity and richness of the flora, but also the structure of Cashew agro-ecosystems. For the analyzes of vegetation structure, tree density, basal area and biovolume were calculated. The inventory included trees with a dbh greater than or equal to 5 cm on an area of ​​1 ha per plot. The experimental device installed is a complete random Fisher block with five repetitions. A total of 7849 individuals in 17 families, 20 genera and 38 species were recorded. Species Important value of vegetation cover indicated that Diospyros mespiliformis, Anogeissus leiocarpus, Annona senegalensis and Terminalia laxiflora are the most represented. Combretaceae are the most ecologically important families. Additionally, the grouping of species into four subdivisions showed that the Shannon diversity index varies from 2.18 ± 0.09 - 3.47 ± 0.17 bits, Pielou index vary from 0.98 ± 0.01 - 0.99 ± 0.01, Simpson's index ranges from 0.70 ± 0.18 - 0.93 ± 0.11, density ranges from 102 ± 1.92 - 128 ± 6.36 indiv/ha, basal area ranges from 2.02 ± 0.31 - 12.68 ± 2.01 m²/ha, biovolume ranges from 11.58 ± 1.29 - 68.03 ± 13.21 m3/ha. The Sörensen similarity index is very high with floristic affinities greater than or equal to 90%. The diameters and heights structure show a predominance of young individuals for the diameter and height classes on all plots. The most represented species associations are legumes (Arachis hypogeae: 40.54%) and native fruit trees (Vitellaria paradoxa: 15%). These results show the contribution of Cashew agro-ecosystems in biodiversity conservation.
Figures
PreviousNext
Article

Query parameters

Keyword:  Density

View options

Citations of

Views of

Downloads of