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Most of the measures of income inequality are derived from the Lorenz curve, and many authors state that the Gini index is the best single measure of inequality. The present paper reviews some of the theorical properties of the Lorenz curve and provides a nonparametric estimate of the Gini index and the almost sure convergence of this estimate. And to confirm the performance of the estimator, an application on real data was carried out.

We have theoretically obtained an expression for the current density in a terahertz field due to hot-electron injection in carbon nanotubes. The injection modifies the stationary distribution function and leads to a qualitative change in the behavior of the current-voltage characteristics and causes absolute negative conductivity. We compared the current-voltage characteristic behavior at different injection rates and observed a drastic change in the current density and absolute negative conductivity values. We propose that carbon nanotubes with hot-electron injection may be useful for high-frequency applications.

This paper addresses some properties of vector measures (Banach space valued measures) as well as topological results on some spaces of vector measures of bounded variation.

We present theoretical framework investigations of the influence of temperature variation on the electrical conductivity of zigzag carbon nanotubes (CNTs) under the applied homogeneous axial dc field. This study was done semiclassically by solving Boltzmann transport equation to derive the current density of zigzag CNT as a function of homogenous axial dc field and temperature. Plots of the normalized current density versus homogeneous dc field applied along the axis of semiconducting zigzag CNTs as room temperature increases from 293 to 299 K revealed a significant increase in electrical conductivity, whereas in metallic zigzag CNTs, almost constant or a negligible decrease in electrical conductivity is observed. The study predicts semiconducting zigzag CNT as a potential material for temperature sensors since it exhibits a faster response and a substantially higher sensitivity to room temperature changes than the metallic counterpart. The electrical conductivity of metallic zigzag CNTs increases immensely as the temperature is reduced to a very low value which could probably lead to a potential superconductivity property that usually occurs at very low temperatures. These potential temperature sensors and superconductors of nanomaterial have vast applications in current-day science and technology.

The role of institutions in both the inflow and the impact of foreign direct investment is of great im¬portance. The quality of institutions in a country can direct investment towards improving growth. This paper analyzes the individual and combined effect of foreign direct investment and institutions on economic growth in Ghana. The paper used the Auto Regressive Distributed Lag (ARDL) tech¬nique for secondary data obtained from 1995 to 2019. All data series, except for the quality institution index, were drawn from the World Bank Development Indicators. Institutional Quality Index data was obtained from the Heritage Foundation’s Economic Freedom Index website. The results of the ARDL model indicate that foreign direct investment and a quality institutional index together have a significantly positive effect on a country’s economic growth compared to their individual effects in both the short and long run. The study recommends that government policies should be aimed at attracting foreign direct investment while strengthening institutions and regulations to enhance output growth.

We have studied the axial resistivity of chiral single-walled carbon nanotubes (SWCNTs) in the presence of a combined direct current and high frequency alternating fields. We employed semiclassical Boltzmann equations approach and compared our results with a similar study that examined the circumferential resistivity of these unique materials. Our work shows that these materials display similar resistivity for both axial and circumferential directions and this largely depends on temperature, intensities of the applied fields and material parameters such as chiral angle. Based on these low-temperature bidirectional conductivity responses, we propose chiral SWCNTs for design of efficient optoelectronic devices.

The novel effect of direct current generation by carbon nanotubes with hot electron injection which may arise due to an electromagnetic radiation with commensurate frequencies has been theoretically investigated using the semiclassical Boltzmann kinetic equation with relaxation time assumed constant. The nonlinearity of the current voltage characteristics and the chiral effects have been considered. We note that the direct current is a result of the strong nonprabolicity of the energy of the carbon nanotubes for the case where it Bloch oscillates. It is shown that the novel expression for the direct current generation strongly and significantly dependence on the hot electron injection rate, which leads to strong oscillatory behavior and the shift of the regions of absolute negative conductivity from low to higher dimensionless amplitude β values with increasing injection rate. We predict that carbon nanotubes with hot electron injection may be useful for generation of direct current.

Aims: We aimed at auditing hernia surgeries performed at a secondary care center and determine the outcome of surgery based on the grade of operating surgeon. Study Design: A single center retrospective study. Place and Duration of Study: Department of Surgery of Ashanti regional Hospital between October 2015 to September 2018. Methodology: We included 259 patients, age ranging between 1 and 84 years, who underwent external hernia surgeries. Information retrieved included patient demographics, type of hernia, duration of hernia, whether hernia was emergency or elective, method of repair, whether surgery was performed by a surgeon or non-surgeon and early post-operative complications. Data was analyzed using PASW Statistics for Windows, Version 18.0. Chicago: SPSS Inc SPSS. Bivariate analysis was done to ascertain relationship between complications and operating doctor. Results: A total of 259 hernia surgeries were performed over the study period. There were 186 (71.8 %) males and 73 (28.2 %) females, age range of 1 to 84 years. There were 66 (25.5%) children and 193(74.5%) adults. Children in their first decade were the majority (22.4%) age group followed by adults in their 5th decade (17%). Inguinal hernia was the most common (75.7%) type of hernia, 49 (18.9%) children and 147(56.6%) adults. There were 32 (12.4%) emergencies. Small bowel (20) was the most common content found in the hernia sac with 6 of them being gangrenous. Hematoma was the most common early complication. The majority (63.7%) of the cases were performed by the general surgeon and (20.1%) by house officers (interns) under supervision. Complications like haematoma, surgical site infection and acute urinary retention were more likely to occur in the non-surgeon operators. There was no statistically significant relation between the grade of operating surgeon and Haematoma (p = 0.28) and surgical site infection (p= 0.76). Conclusion: Hernias are common in children in the first decade and in adults in the 5th decade. With a well-structured training programme non-surgeon physicians can be trained to perform hernia surgeries with relatively low complication.

We show that Hall-like current can be induced by acoustic phonons in a nondegenerate, semiconductor fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach in the hypersound regime (q is the modulus of the acoustic wavevector and is the electron mean free path). We observed a strong dependence of the Hall-like current on the magnetic field, H, the acoustic wave frequency, , the temperature, T, the overlapping integral, , and the acoustic wavenumber, q. Qualitatively, the Hall-like current exists even if the relaxation time does not depend on the carrier energy but has a strong spatial dispersion, and gives different results compared to that obtained in bulk semiconductors. For and , the Hall-like current is in the absence of an electric field and in the presence of an electric field at 300 K. Similarly, the surface electric field due to the Hall-like current is in the absence of an external electric field. In the presence of an external electric field, and for at 300 K. q and can be used to tune the Hall-like current and of the FSWCNT. This offers the potential for room temperature application as an acoustic switch or transistor, as well as a material for ultrasound current source density imaging (UCSDI) and AE hydrophone device in biomedical engineering.

Acoustoelectric effect (AE) in a non-degenerate Fluorine modified single walled carbon nanotube (FSWCNT) semiconductor is studied theoretically using the Boltzmann’s transport equation. The study is done in the hypersound regime i.e. , where q is the acoustic phonon wavenumber and is the electron mean free path. The results obtained are compared with that of undoped single walled carbon nanotube (SWCNT). The AE current density for FSWCNT is observed to be four orders of magnitude smaller than that of undoped SWCNT with increasing temperature, that is . This is because the electron-phonon interactions in SWCNT are stronger than FSWCNT. Thus, there are more intra-mini-band electrons interacting with the acoustic phonons to generate a higher AE current in SWCNT than in FSWCNT. This has been observed experimentally, where the electrical resistance of FSWCNT is higher than pristine SWCNT i.e. . The study shows the potential for FSWCNT as an ultrasound current source density imaging (UCSDI) and AE hydrophone material. However, FSWCNT offers the potential for room temperature applications of acoustoelectric device but other techniques are needed to reduce the resistance.

Acoustoelectric effect (AE) in a non-degenerate fluorinated single walled carbon nanotube (FSWCNT) semiconductor was carried out using a tractable analytical approach in the hypersound regime , where q is the acoustic wavenumber and is the electron mean-free path. In the presence of an external electric field, a strong nonlinear dependence of the normalized AE current density , on ( is the electron drift velocity and is the speed of sound in the medium) was observed and depends on the acoustic wave frequency, , wavenumber q, temperature T and the electron-phonon interactions parameter, . When , decreases to a resonance minimum and increases again, where the FSWCNT is said to be amplifying the current. Conversely, when , rises to a maximum and starts to decrease, similar to the observed behaviour in negative differential conductivity which is a consequence of Bragg’s reflection at the band edges at T=300K. However, FSWCNT will offer the potential for room temperature application as an acoustic switch or transistor and also as a material for ultrasound current source density imaging (UCSDI) and AE hydrophone devices in biomedical engineering. Moreover, our results prove the feasibility of implementing chip-scale non-reciprocal acoustic devices in an FSWCNT platform through acoustoelectric amplification.

Pterocarpus mildbreadii leaves and stem bark have been exploited in Nigeria, in the area of alternative medicine, due to their numerous biological properties. The upsurge in the search for new chemical agents to replace conventional drugs, prompted this study. The study was carried out for the first time, in the area of isolation and structural elucidation of bioactive compounds, from the ethanolic extracts of the stem bark of Pterocarpus mildbreadii. The ethanol extract of the stem bark was separated using column chromatographic technique. The fractions obtained were screened for antioxidant activity in a DPPH assay. The active fraction was further purified and the structure elucidated by subjecting it to a number of identification instruments, such as FTIR, MS and 1D &2D NMR spectroscopy. The FTIR analysis of isolated bioactive compound gave the following λ max: 3400-2500 cm-1 a broad band characteristic of a carboxylic acid functional group and 1740 cm-1 carbonyl stretch. The mass spectrum game a molecular ion peak at m/z 282 consistent with the molecular formula C18H34O2. The proton NMR showed a doublet of doublet of doublet at 4.9, 5.3 and 5.8 ppm attributed to vinyl protons, two proton multiplets at 1.6,1.3, and 1.2 ppm; and a three proton triplet at 0.9 ppm. The HMBC and 13C NMR showed the presence of a carboxylic carbon at 176 ppm and vinylic carbons at 135 and 143 ppm respectively; the methyl carbon was observed at 14.12 ppm. On the basis of spectral analysis, results obtained suggested compound was cis-vaccenic acid and was confirmed by comparison with literature data. Isolated compound has antioxidant activity, with a maximum percentage scavenging activity of 89.66. The present study lends credence to the use of the plant in traditional medicine and posits pterocarpus mildbreadii as a rich source of secondary metabolites which can find application in the pharmaceutical industries.

Herein, we report on a giant thermoelectric figure of merit of a non-degenerate fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach and the phonon lattice Boltzmann model (LBM). We investigate the influence of the doping concentration, and the overlapping integrals on the ZT. The ZT and the temperature range of operation can be tuned using the doping (impurity) concentration and the overlapping integrals, respectively. The lattice thermal conductivity obtained using the phonon LBM was calculated to be 107.2 W/mK which yielded a ZT greater than 20. Interestingly, the ZT obtained is higher than what has been reported in superlattices, (ZT~1.4) and superlattice nanowire, (ZT~ 4) at 300 K, making FSWCNT a potential candidate for thermoelectric applications.

We perform self-consistent analysis of the Boltzmann transport equation for momentum and energy in the hypersound regime i.e., $$ql \gg 1$$ q l ≫ 1 ($$q$$ q is the acoustic wavenumber and l is the mean free path). We investigate the Landau damping of acoustic phonons ($$LDOAP$$ LDOAP ) in graphene nanoribbons, which leads to acoustoelectric current generation. Under a non-quantized field with drift velocity, we observed an acoustic phonon energy quantization that depends on the energy gap, the width, and the sub-index of the material. An effect similar to Cerenkov emission was observed, where the electron absorbed the confined acoustic phonon energy, causing the generation of acoustoelectric current in the graphene nanoribbon. A qualitative analysis of the dependence of the absorption coefficient and the acoustoelectric current on the phonon frequency is in agreement with experimental reports. We observed a shift in the peaks when the energy gap and the drift velocity were varied. Most importantly, a transparency window appears when the absorption coefficient is zero, making graphene nanoribbons a potential candidate for use as an acoustic wave filter with applications in tunable gate-controlled quantum information devices and phonon spectrometers.

Objectives: The present study aimed to generate intensity-modulated beams with compensators for a conventional telecobalt machine, based on dose distributions generated with a treatment planning system (TPS) performing forward planning, and cannot directly simulate a compensator. Materials and Methods: The following materials were selected for compensator construction: Brass, Copper and Perspex (PMMA). Boluses with varying thicknesses across the surface of a tissue-equivalent phantom were used to achieve beam intensity modulations during treatment planning with the TPS. Beam data measured for specific treatment parameters in a full scatter water phantom with a 0.125 cc cylindrical ionization chamber, with a particular compensator material in the path of beams from the telecobalt machine, and that without the compensator but the heights of water above the detector adjusted to get the same detector readings as before, were used to develop and propose a semi-empirical equation for converting a bolus thickness to compensator material thickness, such that any point within the phantom would receive the planned dose. Once the dimensions of a compensator had been determined, the compensator was constructed using the cubic pile method. The treatment plans generated with the TPS were replicated on the telecobalt machine with a bolus within each beam represented with its corresponding compensator mounted on the accessory holder of the telecobalt machine. Results: Dose distributions measured in the tissue-equivalent phantom with calibrated Gafchromic EBT2 films for compensators constructed based on the proposed approach, were comparable to those of the TPS with deviation less than or equal to ± 3% (mean of 2.29 ± 0.61%) of the measured doses, with resultant confidence limit value of 3.21. Conclusion: The use of the proposed approach for clinical application is recommended, and could facilitate the generation of intensity-modulated beams with limited resources using the missing tissue approach rendering encouraging results.

Accuracy of dose delivered, image quality and some technical parameters of the Fujifilm – Amuletf full field digital mammography X-ray equipment has been undertaken. The study was conducted to review the overall condition of the first full – field digital mammography equipment in Ghana with the aim of optimizing mammography practice. Quality control assessment and Mean glandular dose estimation was performed using the International Atomic Energy Agency Human Health Series 2 and 17 protocol and the European guidelines for quality assurance in breast cancer screening and diagnosis. Quantitative image analysis was performed with ImageJ software using the “Rose Model”. The results from the quality control test performed indicates that the system is functioning well. Signal-to-noise and contrast-to-noise values determined from images shows that the images are of standard quality. With the exception of 9.00 mm breast thickness which recorded a displayed Mean Glandular Dose (MGD) of 7.17 mGy, all other MGD calculated or displayed were well within the acceptable level. The percentage difference between the calculated and console displayed MGD was within the acceptable difference level of 50%. The phantom dose values obtained can be used as baseline data for future studies which can assist in setting optimization activities. The mammography X-ray equipment at the Korle-Bu teaching Hospital, Accra – Ghana is functioning under optimized conditions. It is therefore recommended for further usage. Keywords: Mammography, Mean glandular dose, Image quality, Quality control, Polymethylmethacrylate, Automatic exposure control

Much of the global agricultural by products go waste, especially in developing nations where much of their revenues depend on the exports of raw agricultural products. Such waste streams, if converted to “value added” products could serve as additional source of revenue while simultaneously having a positive impact on the socio-economic well being of the people. We present a preliminary investigation on utilizing chemical activation technique and ball milling to convert agricultural waste streams such as cocoa pod, coconut husk, palm midrib and calabash commonly found in Ghana into ultra-high surface area activated carbon. Such activated carbons are suitable for myriads of applications in environmental remediation, climate management, energy storage and conversion systems (batteries and supercapacitors), and improving crop productivity. We achieved BET surface area as high as ∼ 3000 m2/g.

In medical exposure dose to patients are determine by input parameters including mAs, kVp, pitch factor among other factors. The aim of this study is to provide procedure and protocol of how to assess patients’ dose (organ and effective dose) estimates with preset eff mAs and standard kVp. This is to determine a tradeoff between patient’s dose and the image quality before imaging. In addition to providing appropriate clinical recommendation for clinicians for dose management during CT scan. MVL DICOM application software was used to access image data during abdominal CT scan. Organ and effective dose estimates were estimated as developed by ICRP 103 recommendations. Where on the image data, using MVL platform detail information of the mAs, kVp, CTDIvol and DLP were available for recording. The weighted CTDI (CTDIW) was estimated by multiplying the volume CTDI (CTDIVOL) by the pitch factor. Which was used to estimate organ dose using the normalized organ dose factor and the effective dose was estimated by the product of the region-specific normalizing constant and the dose length product. The mAs is the effective Milliameter per second, which were calculated by dividing the mAs by the pitch factor. The relationship between input and output parameters were modeled as the final component of the modeling process in a form of GUI applications format. This was done to establish the various process and procedures involve in abdominal scan for dose managements. The coding process involve the use of written visual basic code to design an interface and integrated on the MVL application platform for clinical application. The GUI has been recommended for use by various stake holders in CT operations.

The quantities that determine the relative image noise level by either increasing or reducing its value are photon quality (kVp) and photon quantity (mAs). This study is to determine the effect of LET, energy and particle fluence on the renal surface area during abdominal CT scan. The method involve extracting three exposure parameters from image data using MVL DICOM application software including: kVp, mA and scan time. The kVp or the photon peak energy which is applied in the A-P direction during abdominal CT scan was used to estimate linear energy transfer. While the particle fluence and the energy fluence were estimated from the effective mAs and the kVp on the total renal surface respectively. The effective mAs were estimated by dividing the mAs by the average pitch factor of approximately 0.813. In all the examinations, the average protocol setting in terms of exposure time and kilovolts peak were 500s and 120keV respectively. While the average protocol in all the centers recorded a mean effective milliamp second (mAs) of 59.27 mAs and tube current of 94.22A. The influence of these parameters on abdominal scan depends on the scan time, scan scope, the size of the renal surface area (RSA) which has varied values. The effects of effective mean mAs per unit mean renal surface area, described as mean effective particle fluence were 1.32mAs/cm2 and 1.50 mAs/cm2 for male and female respectively. The energy fluence, which is the photon energy per unit renal surface area estimated to have a mean value of 4.02 keVcm-2 and 4.51 keVcm-2 for male and female respectively. In addition, the maximum and minimum variations of all the measured parameters. The LET, which described the lost in photon energy as it traverses across the renal tissues in the A-P direction was estimated, with a mean value of 2.60 keV/µm and 2.67 keV/µm for male and female respectively. The maximum and minimum LET values were 4.49 keV/µm and 1.90 keV/µm for male and 5.26 keV/µm and 1.98 keV/µm for female respectively. The maximum measured values were below the critical LET values estimated to be between 15 to 20 keV/µm. These estimated risk parameters were used to predict the effect on abdominal and kidney tissues using the various modeled equations.

The study provided a simple method of using voxel count method to estimate organ volume together with x-ray attenuation coefficient principle. The aim is to discuss the role of x-ray attenuation coefficient in CT organ volume measurements using voxel count method. The method involve using the principle of linear attenuation coefficient which describes the fraction of a beam of x-rays or gamma rays that is absorbed or scattered per unit thickness of the absorber to enable tissue differentiation and hence the used of volume elements method, where the body is literally divided into 3-dimensional rectangular boxes with known size and thickness. This value basically accounts for the number of atoms within a specified distance of a material and the probability of a photon being scattered or absorbed from the nucleus or an electron of one of these atoms. A graph of linear attenuation coefficients versus radiation energy are used to separate between various body tissues. At a specific energy the difference in attenuation between two tissues is greatest at a specific radiographic contrast in an image. Hence, this variation enable a separation and subsequent measurements of varied tissues. Therefore, it is extremely useful to determine various linear attenuation coefficients of tissues to enable various variations to be determine for clinical application.

The incidence of liver diseases is increasing globally, and many patients in developing countries are resorting to the use of herbal products as treatment. This study was aimed at establishing the safety and effectiveness outcomes for patients with deranged liver panel treated with a Ghanaian finished polyherbal product. The product Heptonica is prepared by CPMR from three medicinal plants: Bidens pilosa, Citrus aurantifolia, and Trema orientalis. Fifty (50) participants with clinical and biochemical signs of liver impairment were purposively recruited and treated for a period of 28 days. Participants received Heptonica at a dose of 30 mL 8 hourly after meals for the treatment period. Clinical and biochemical evaluation (liver panel test, renal function test, haematology, and urinalysis) of subjects for the safety and effectiveness of the product was undertaken at days 0 (baseline), 14, and 28. Compared to the baseline values, Heptonica did not have any untoward effect on renal function, haematological parameters, and urine parameters of subjects. Clinical and liver panel results of the participants also improved compared to the baseline: serum aspartate transaminase (AST) (p

The radius dependence of the electrical conductivity of metallic and semiconducting zigzag carbon nanotubes (CNTs) is theoretically studied. The investigation was done semiclassically by solving the Boltzmann transport equation to derive current density as a function of a homogenous axial dc field and radius of the tube. The analysis was numerically carried out by varying the radius of the materials at a constant temperature. Plots of the normalized current density versus dc field applied along the axis of both materials are presented. We observed that in the case of the metallic zigzag CNTs as the radius increases, the electrical conductivity decreases. On the other hand, in the semiconducting zigzag CNT there was an increase as radius increases. This research shows that thinner metallic zigzag CNTs and thicker semiconducting zigzag CNTs are better conductors of electricity. This investigation therefore offers way of obtaining higher electrical conductivity in both materials without doping. This study therefore shows applications in the development of current conducting nano-devices for scientific systems.

CT images are the most common imaging modality after conventional X-ray imaging. There are used in order to determine organ position, location and size in relation to treatment area for treatment planning and for diagnoses of diseases. The general aims of the study is to design a comprehensive clinical decision support application software for patients' dose optimization. The design of the GUI involve the use of mathematical modeling procedure where the modeled equations reduces the data from empirical measurements to real clinical application process for implementation. The final component of the modeling process is the GUI applications. This was done in two different process and procedures. The first was the coding process where a software was developed with written C++ code and integrated on the data capturing application platform for clinical application. The second was the visual indicators where the shape and size were modeled to represent the variation in age and gender that exist between the various model equations. The GUI are then used by radiographers to predict and plan the choice of input parameters for effective managements of doses to patient undergoing abdominal CT examination. Finally, a GUI and CAD models were designed to adequately reflect the comfortable working process of all the mathematical model equations. Reference effective abdominal and renal dose parameters have been established and developed in a data base for clinical application. In addition, the displayed interface on the DICOM interface enable the prediction of CTDI and DLP parameters with known kVp and mAs parameters before imaging.

The study was done to establish the relationship between measured renal volume and body parameters to estimate standard reference value of renal volume related body parameters (RV-BMI, RV-BSI and RV-BSA) in Ghana for clinical application. The estimates were done based on age and gender variation and compare the established standard reference renal volume with its related body parameters. The weight and BMI measuring machine together with tape measure and glass beaker were the measuring tools used. The procedure involve measurement of body height and weight and using the estimated values to calculate BMI with the BMI calculator. It also involve using DuBois formula to estimate local standard reference values of BSI and BSA in Ghana. The reference standard renal volume was determined using water displacement with the Archimedes' principle to confirm the established values in Ghana. These value were compare with established standard reference renal volume model in Ghana which were estimated using abdominal images on MeVisLab application software platform and determined the relationship between these parameters. The determined Ghanaian standard reference renal volume were: 146.74cm3, 151.76cm3, 142.04cm3 and 148.29cm3 for male and female, with its corresponding right and left kidneys respectively. The estimated mean BMI, BSI and BSA were; 25.19kg/m2 39.81 kg/m2 and 2.02m2 for male and 21.91kg/m2 36.58kg/m2 and 1.69m2 for female respectively. Hence from these set of values, the relationship between renal volume and its related BMI was determined to be 6.04cm3-kg/m2 for male and 6.47cm3-kg/m2 for female. While the male RV related-BSA was also determine to be 74.05cm3-m2 and 84.09cm3-m2 for female. Finally, the renal volume related-BSI was also estimated to be 3.81cm3-kg/m2 for male and 3.88cm3-kg/m2 for female. The standard reference renal volume related BMI, BSI and BSA are recommended to be used for renal assessment for clinical application in Ghana.

The study is to estimate renal and effective dose during abdominal MDCT scan using image data for dose optimization for purposes of radiation protection in Ghana. In addition dose influencing parameters including CTDIVOL DLP and MSAD were recorded and compared with ICRPICRU AAPM EU and IAEA dose optimization recommendations. All the measurements were done during abdominal MDCT examination. The measured parameters were part of image data on the MeVisLab DICOM application software platform. The total photon fluence mAs per area and the photon energy fluence kVp per area on the abdominal and renal surface was also determined. Renal and effective dose were estimated using ICRP publication 103 recommendations. The results of the measured parameters based on the average renal surface area of 29.52cm2 and 30.67cm2 for the right and left kidney respectively shows that The mean dose parameters were 6.33mGy 7.78mGy 936.25mGy cm 5.76mGy 10.99mSv and 14.09mSv for CTDIV CTDIW DLP MSAD RD and E respectively. The average values were lower than the general recommended average critical values but this seems misleading based on the fact that 37 of the individual dose and exposure parameters exceeded the recommended critical values. A tradeoff between patient radiation dose and image quality in abdominal CT has been established. Where at a mean SNR of 6.6 decibels an adequate images were produce to answer all the clinical questions with an average effective dose of 14.09mSv and renal dose of 10.99mSv. Radiation dose during x-ray CT imaging is an important patient safety concern. Reducing radiation dose result in a reduction of the risk to patient however reducing dose also reduces the signal strength and thereby reduces the signal to noise ratio in the resulting CT image hence the image quality is affected. It is recommended that the established reference values be use as clinical advisory mechanism to protect patience and clinicians. It is also recommended that the studies should be carry out periodical to estimates the abdominal effective dose in all the centers.

Although the use of CT in medical diagnosis delivers radiation doses to patients that are higher than those from other radiological procedures, lack of proper optimized protocols could be an additional source of increased dose in developing countries. The aims of this study is to determine the variations of doses to patients undergoing CT scan using four different CT scanners with different CT scanning protocols for the purposes of optimizations and to compare with other available international standard and guidelines. The method involve the use of patients scanning protocol and image data to estimate patient body regional doses with four common CT examinations. These were obtained from four CT units/hospitals in Ghana. A large variation of mean body regional doses among different CT scanners were observed for similar CT examinations. These variations largely originated from different CT scanning protocols used, with different CT scanner type. The measured CTDIVOL with GE Lightspeed VCT 64 scanner for head, hest, abdomen and pelvis were 7.7mGy, 12.5 mGy, 14.4 mGy, and 12.9 mGy, respectively. Similarly, Philip 16 scanner recorded 6.6mGy, 13.1mGy, 14.8mGy, and 14.5mGy respectively. Furthermore, Siemen Emotion 16 scanner recorded 5.9mGy, 14.2mGy, 16.8mGy and 12.0mGy respectively. While, Toshiba Aquilion one scanner had CTDIVOL value which varies as 7.2mGy, 13.4mGy, 15.2mGy and 13.5mGy respectively. In conclusion the values were mostly lower than the values of CTDI and DLP as reported in literature for EC, IAEA, ICRP, ACR and AAPM Guidelines.

The study is based on measurements of renal dimensions to determine standard reference renal volume model and renal volumetric ellipsoid coefficient. Two methods, Voxel count method and rotational renal ellipsoid equation were the two measuring tools used with an integrated MVL application software platform. The procedure involve measurement of linear dimensions together with using the snake technique to draw the region of interest (ROI) for the volumetric measurements. These were done to obtain: renal length, lateral diameter, A-P diameter and the total number of voxels to estimates the renal volume. These parameters were used to calculate renal volume using the rotational renal ellipsoid equation as well as using the Minitab statistical software to model renal volume equation. The reference standard renal volume was also determined using water displacement with the Archimedes' principle. The average renal shape index and its dispersion (i.e. covariance matrix) was approximately 1±0.02. The male average measured values for right and left kidneys were as follows: renal length, 103.35cm and 105.13cm, lateral diameter, 60.79 and 60.40 and A-P diameter, 44.12 and 44.95 and renal volume; 146.74cm3 and 151.76cm3 respectively. Furthermore, the female average measured values for right and left kidneys were as follows: renal length, 101.43 and 102.98, lateral diameter, 59.20 and 59.02 and A-P diameter, 43.09 and 44.82, renal volume 142.04cm3 and 148.29cm3 respectively. The average estimated renal volumetric ellipsoid coefficient (VeC) was 0.53. However, various variations for both male and female, with their corresponding right and left kidneys were, 0.5283, 0.5297, 0.5280 and 0.5304 respectively. The reference renal dimensions including the standard renal volume and renal volumetric ellipsoid coefficient are recommended for clinical application in Ghana.

The study is based on estimate of CTDI and DLP values for patients' dose optimization procedures. Technical parameters were obtained for three groups of randomly selected patients undergoing abdominal CT examinations of 320 patients of age 20-80 years. The measured values were obtained on image data and the standard reference values of various machines were obtained from service manual as part of QC/QA and the recommended values from ICRP publication 103. The mean CTDI and DLP parameters were; 6.33mGy and 936.25mGy respectively. Furthermore, the mean recorded values of CTDIVOL values were well within ICRP recommendation when the protocol was completed in one scan. On the other hand, in the case of multiscan the total CTDIVol was higher than the ICRP recommendations. While the mean DLP values were higher than the recommended value of 780 mGy-cm by ICRP publication 103. Finally, approximately 37% of the total varied CTDI and DLP values were higher than the recommended dose by ICRP publication 103.

Acoustoelectric current ( j ac ) in Free-Standing Graphene (FSG) having degenerate energy dispersion at low temperatures T ⪡ T BG ( T BG is the Block-Gruneisen temperature) was studied theoretically. We considered electron interaction with in-plain acoustic phonons in the hypersound regime (sound vibration in the range 10 9 − 10 12 Hz ). The obtained expression for j ac was numerically analyzed for various temperatures ( T ) and frequencies ( ω q ) and graphically presented. The non-linear dependence of j ac on ω q varied with temperature. This qualitatively agreed with an experimentally obtained result which deals with temperature dependent acoustoelectric current in graphene [21] .

Amplification of acoustic waves in Armchair Graphene Nanoribbon (AGNR) in the presence of an external electric and magnetic fields was studied using the Boltzmann's kinetic equation. The general expression for the amplification (Γ⊥/Γ0) was obtained in the region ql⪢1 for the energy dispersion e(p→) near the Fermi point. For various parameters of the quantized wave vector (β), the graphs of Γ⊥/Γ0 against the electric field (Ex→), the acoustic wave-number (q→), the energy gap (Eg) and the dimensionless factor (Ωτ0) were numerically analyzed. The results showed a linear relation for Γ⊥/Γ0 with Ex→ but non-linear for q→ and Ωτ0. The observed amplification can lead to SASER in Armchair Graphene Nanoribbon (AGNR).

Hot electrons injection in carbon nanotubes (CNTs ) where in addition to applied dc field ($\mathbf{E}$), there exist simultaneously a quasi-static ac electric field (i.e. when the frequency $\omega$ of ac field is much less than the scattering frequency $v$ ($\omega\ll v$ or $\omega\tau\ll 1$, $v =\tau^{-1}$, where $\tau$ is relaxation time) is considered. The investigation is done theoritically by solving semiclassical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field ($\mathbf{E}$) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided $\omega\tau\ll 1$ (i.e. quasi- static case). With strong enough axial injection of the hot electrons , there is a switch from NDC to positive differential conductivity (PDC) about $\mathbf{E} \geq 75 kV/cm$ and $\mathbf{E} \geq 140 kV/cm$ for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

Studies have shown that there is high radiation exposure to medical staff during computed tomography fluoroscopy (CTF)-guided procedures. This study aims to investigate staff dose reduction techniques considering the CTF gantry positioning in the room and room dimensions in addition to the conventional use of thyroid collars, aprons and eye goggles. A Toshiba Aquilion One 640 slice CT scanner and CTF room were modelled using SimpleGeo. Standing and supine adult mesh phantoms were used to represent the staff and patient. The models were spatially put together on one platform using VOXEL2MCNP. Based on this, MCNPX input files were generated for the studies. CTF gantry and staff positions, and CTF room size were varied for different scenarios. Effective, eye lens and thyroid dose to staff were estimated for each scenario. Additional means of possible dose reduction with respect to positioning of the CTF device and room layout are discussed.

Herein, we present a tunable axial power factor ( P z z) in a nondegenerate fluorine-doped single-walled carbon nanotube (FSWCNT) using a tractable analytical approach. We derived the expressions for the electrical conductivity ( σ), thermopower ( α), and power factor ( P) as a function of temperature. Additionally, we investigated the influence of doping concentration ( n o), constant electric field ( E o), and overlapping integrals ( Δ s and Δ z) on their behavior. The intensity of the axial power factor ( P z z) and the operational temperature range can be tuned using the constant electric field, doping (carrier), and overlapping integrals, respectively. Applying the temperature field to the FSWCNT induces high-frequency carrier dynamics that critically depend on the magnitude of the temperature gradient. There exist two dynamic regimes that depend on the temperature gradient and carrier’s initial position. The carrier drifts through the FSWCNT and is allowed to perform drifting periodic orbits (in THz frequencies), resulting in the resonant enhancement of P z z. Alternatively, inducing Bloch-like oscillations (in THz frequencies) cause ultra-high negative differential velocity without domain formation using an adequate temperature field. Moreover, we compare the P z z of the FSWCNT to that of the superlattice (SL) ( P z z S L), which shows that the P z z of the FSWCNT is 8 orders of magnitude greater than that of the SL. It is worth noting that the large P z z obtained and the ability to tune the FSWCNT to operate at high temperatures make the FSWCNT a potential candidate for thermoelectric applications.

Using the Boltzmann transport equation within the semi-classical approximation with constant relaxation time, we theoretically studied the dynamics of electrons in chiral single wall nanotubes (SWNTs) subjected to a temperature gradient (∇T) in the presence of a combined direct current and high frequency alternating fields. We obtained an expression for the resistivity (ρ c ) of the SWNTs which varies with temperature and depends among others on material’s chiral angle (θ h), dc field strength (Eo) and ac field amplitude (Es). Our results show that chiral SWNTs exhibit metallic behavior with resistivity increasing approximately linearly with temperature over a wide temperature range well above 100 K. Based on the low chiral resistivity obtained for the SWNTs at room temperatures, we propose these materials as good candidates for possible optoelectronic applications.

We studied theoretically the absorption of acoustic phonons in the hypersound regime in Fluorine modified Carbon Nanotube (F-CNT) $\Gamma_q^{F-CNT}$ and compared it to that of undoped Single Walled Nanotube (SWNT) $\Gamma_q^{SWNT}$. Per the numerical analysis, the F-CNT showed less absorption to that of SWNT thus $\vert\Gamma_q^{F-CNT}\vert < \vert\Gamma_q^{SWNT}\vert $. This is due to the fact that Fluorine is highly electronegative and weakens the walls of the SWNT. Thus, the $\pi$-electrons associated with to the Fluorine which causes less free charge carriers to interact with the phonons and hence changing the metallic properties of the SWNT to semiconductor by the doping process. From the graphs obtained, the ratio of hypersound absorption in SWNT to F-CNT at $T = 45K$ is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 29$ whilst at $T = 55K$, is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 9$ and at $T = 65K$, is $\frac{\Gamma_{(SWNT)}}{\Gamma_{(F-CNT)}}\approx 2$. Clearly, the ratio decreases as the temperature increases.

We report on a theoretical investigation of a direct current generation in carbon nanotubes (CNTs) that are stimulated axially by terahertz (THz) field. We consider the kinetic approach based on the semiclassical Boltzmann’s transport equation with constant relaxation time approximation, together with the energy spectrum of an electron in the tight-binding approximation. Our results indicate that for strong THz-fields, there is simultaneous generation of DC current in the axial and circumferential directions of the CNTs, even at room temperature. We found that a THz-field can induce a negative conductivity in the CNTs that leads to the THz field induced DC current. For varying amplitude of the THz-field, the current density decreases rapidly and modulates around zero with interval of negative conductivity. The interval decreases with increasing the amplitude of the THz-field. We show that the THz-field can cause fast switching from a zero DC current to a finite DC current due to the quasi-ballistic transport, and that electron scattering is a necessary condition for switching.

We investigate theoretically the high frequency complex conductivity in carbon nanotubes that are stimulated axially by a strong inhomogeneous electric field of the form E(t)=E0+E1cos(ωt). Using the kinetic approach based on Boltzmann’s transport equation with constant relaxation time approximation and the energy spectrum of the electron in the tight-binding approximation, together with Bhatnagar-Gross-Krook collision integral, we predict high-frequency nonlinear effects along the axial and the circumferential directions of the carbon nanotubes that may be useful for the generation of high frequency radiation in the carbon nanotubes.

We study temperature effect on anomalous viscosity of Graphene Hall fluid within quantum many-vortex hydrodynamics. The commonly observed filling fractions, $��$ in the range $0 < ��< 2$ is considered. An expression for anomalous viscosity dependent on a geometric parameter-Hall expansion coefficient, is obtained at finite temperatures. It arises from strained induced pseudo-magnetic field in addition to an anomalous term in vortex velocity, which is responsible for re-normalization of vortex-vortex interactions. We observed that both terms greatly modify the anomalous viscosity as well as an enhancement of weakly observed v fractions. Finite values of the expansion coefficient produce a constant and an infinite viscosity at varying temperatures. The infinities are identified as energy gaps and suggest temperatures at which new stable quantum hall filling fractions could be seen. This phenomenon is used to estimate energy gaps of already measured fractional quantum Hall states in Graphene., 7 pages, 3 fihures