Absorption of Acoustic Phonons in Fluorinated Carbon Nanotubes with Non-Parabolic, Double Periodic Band

We studied theoretically the absorption of acoustic phonons in the hypersound regime in Fluorine modified carbon nanotube (F-CNT) Γ q F − CNT and compared it to that of undoped single walled carbon nanotube (SWCNT) Γ q SWCNT . Per the numerical analysis, the F-CNT showed less absorption to that of SWCNT, thus ∣ Γ q F − CNT ∣ < ∣ Γ q SWCNT ∣ . This is due to the fact that Fluorine is highly electronegative and weakens the walls of the SWCNT. Thus, the π -electrons associated with the Fluorine causes less free charge carriers to interact with the phonons and hence changing the metallic properties of the SWCNT to semiconductor by the doping process. From the graphs obtained, the ratio of hypersound absorption in SWCNT to F-CNT at T = 45 K is Γ SWCNT Γ F − CNT ≈ 29 while at T = 55 K , is Γ SWCNT Γ F − CNT ≈ 9 and at T = 65 K , is Γ SWCNT Γ F − CNT ≈ 2 . Clearly, the ratio decreases as the temperature increases

Amplification of terahertz radiation in carbon nanotubes

We investigate theoretically the feasibility of amplification of terahertz radiation in aligned achiral carbon nanotubes, a zigzag (12,0) and an armchair (10,10) in comparison with a superlattice using a combination of a constant direct current (dc) and a high-frequency alternate current (ac) electric fields. The electric current density expression is derived using the semiclassical Boltzmann transport equation with a constant relaxation time. The electric field is applied along the nanotube axis. Analysis of the current density versus electric field characteristics reveals a negative differential conductivity behavior at high frequency, as well as photon assisted peaks. The photon assisted peaks are about an order of magnitude higher in the carbon nanotubes compared to the superlattice. These strong phenomena in carbon nanotubes can be used to obtain domainless amplification of terahertz radiation at room temperature

Rectification due to harmonic mixing of two coherent electromagnetic waves with commensurate frequencies in carbon nanotubes

We report on a theoretical investigation of carbon nanotubes subjected to a pure alternating electric field consisting of two phase-shifted harmonic fields of frequencies ω1 = Ω and ω2 = 2Ω (harmonic mixing) without any direct current bias. We employed a tight-binding approximation for the description of the energy bands of the carbon nanotubes and the Boltzmann transport equation with constant relaxation time approximation. The results are compared to that of a superlattice under similar conditions. The results indicate a direct current generation by the carbon nanotubes due to the harmonic mixing. The described effect is in essence, due to the nonlinearity associated with the non-parabolicity of the electron energy band, which is greater in the carbon nanotubes than the superlattices. The strong effect observed in the carbon nanotubes is attributed to the stark components and the specific dispersion law inherent in hexagonal crystalline structure of the carbon nanotubes

Ultrasonographic Assessment of Liver Size and its Association to Selected Morphometric Parameters of Domestic Dogs in Accra, Ghana

Introduction: The global unpopularity of linear ultrasonographic measurement, due to its inherent subjectivity, contrasts with the safety, portability, low cost, and real-time capabilities of this imaging modality. The increased availability of ultrasounds in veterinary practice in Ghana presents an opportunity to provide ultrasonographic liver size reference ranges to aid the diagnosis of hepatopathies in domestic dogs. Therefore, this study sought to establish ultrasonographic liver size reference ranges of dogs in Accra, Ghana. It also aimed to to investigate the correlation between liver size and selected morphometric parameters in these domestic dogs. Materials and methods: A total of 60 dogs from different domestic breeds, sexes (27 males and 33 females), age ranges (2.82 ± 2.12 years), weights (28.83 ±9.98kg), and body conformation were sampled. Purposive sampling of dogs was performed based on presenting history, clinical signs, physical exam, and blood analysis. Blood samples were collected for serum biochemistry to distinguish between those classified as healthy and those presenting with clinical illness. Additionally, all dogs were subjected to linear ultrasonographic liver size measurements in longitudinal and transverse planes. Results: The findings indicated a strong positive correlation of mean longitudinal sonographic liver measurement with body height, body girth (the widest point of the chest and the rib cage), the distance between the last rib and the tuber coxa, and the distance between the xiphoid and the tuber ischium. Equations were derived from the mean longitudinal sonographic measurement and these body parameters for deep and non-deep-chested breeds. This study helped to establish equations that can be used to estimate the longitudinal liver measurement. Conclusion: This information can be used in clinical settings to help veterinarians (even with basic knowledge of hepatic ultrasonography) to have a fair idea of hepatopathies relating to size