Brownian dynamics of Dirac fermions in twisted bilayer graphene

Brownian dynamics of Dirac fermions in twisted bilayer graphene is investigated within the framework of semiclassical relativistic Langevin equations. We find that under the influence of orthogonal, commensurate ac drives in the periodic ratchet potential of a substrate, the charge carriers in the system exhibit pronounced random dynamics, tuned by the twist angle, making twisted bilayer graphene distinguishable from monolayer graphene. It is shown that as threshold twist angle matches the optimal angle, deterministic running states appear in the limit of weak thermal noise where the diffusion rate is enhanced significantly compared to bare thermal diffusion. Analysis of the real space trajectories and diffusion coefficient illustrates the significant role of thermal noise in the random motion of Dirac fermions. In addition, we find that the Brownian particle shows remarkable ratchet effect as a net current

Bloch dynamics in inversion symmetry broken monolayer phosphorene

We investigate Bloch oscillations of wave packets in monolayer phosphorene with broken inversion symmetry. We find that the real space trajectories, Berry and group velocities of Bloch electron undergo Bloch oscillations in the system. The strong dependence of Bloch dynamics on the crystal momentum is illustrated. It is shown that the spin-orbit interaction crucially affects the dynamics of the Bloch electron. We also demonstrate the dynamics in external electric and magnetic field within the framework of Newton's equations of motion, leading to the geometric visualization of such an oscillatory motion. In the presence of both applied in-plane electric and transverse magnetic fields, the system undergoes a dynamical transition from confined to de-confined state and vice versa, tuned by the relative strength of the fields

Spectrum and Franck-Condon factors of interacting suspended single-wall carbon nanotubes

A low energy theory of suspended carbon nanotube quantum dots in weak tunnelling coupling with metallic leads is presented. The focus is put on the dependence of the spectrum and the Franck-Condon factors on the geometry of the junction including several vibronic modes. The relative size and the relative position of the dot and its associated vibrons strongly influence the electromechanical properties of the system. A detailed analysis of the complete parameters space reveals different regimes: in the short vibron regime the tunnelling of an electron into the nanotube generates a plasmon-vibron excitation while in the long vibron regime polaron excitations dominate the scenario. The small, position dependent Franck-Condon couplings of the small vibron regime convert into uniform, large couplings in the long vibron regime. Selection rules for the excitations of the different plasmon-vibron modes via electronic tunnelling events are also derived.Comment: 23 pages, 8 figures, new version according to the published on

Dynamical symmetry breaking in vibration-assisted transport through nanostructures

A theoretical model of a single molecule coupled to many vibronic modes is presented. At low energies, transport is dominated by electron-vibron processes where transfer of an electron through the dot is accompanied by the excitation/emission of quanta (vibrons). Because the frequency of the $n$th mode is taken as an $n$th multiple of the frequency of the fundamental mode, several energetically degenerate or quasi-degenerate vibronic configurations can contribute to transport. We investigate the consequences of strong electron-vibron coupling in a fully \emph{symmetric} set-up. Several striking features are predicted. In particular, a gate-asymmetry and pronounced negative differential conductance features are observed. We attribute these features to the presence of slow channels originating from the interplay of Franck-Condon suppression of transport channels and spin/orbital degeneracies.Comment: 10 pages, 11 figures, published versio

The descriptive study of anxiety levels among diabetics: insulin users versus non-insulin users

Background: Anxiety is an emotion characterized by an unpleasant state of turmoil often accompanied by nervous behaviours such as pacing back and forth, somatic complaints and rumination. Diabetes is the most metabolically active disease which can influence the psychological state. This study evaluates the anxiety levels among diabetics (Insulin users versus non-insulin users) along with its relation to certain demographic factors like age, sex, education, type of medication and medication compliance.Methods: Hamilton anxiety rating scale (HAM-A) was used to test the anxiety levels in 187 diabetic patients visiting the diabetic clinic and research centre, Nishtar Hospital, Multan and other diabetic clinics in the area. 97 (51.87%) patients of the total sample are males and 90 (48.12%) patients are females.Results: In this study, 170 (91%) had type 2 diabetes while 17 (9%) suffered from Type 1 Diabetes. 66.66% of the patients in the sample were insulin users while 34.34% were non-insulin users. The overall mean anxiety level in insulin users is 24.55 and in non-insulin users is 23.92.Conclusions: Our study showed a high prevalence of anxiety levels in insulin users as compared to non-insulin users. Certain symptoms like anxious mood, tension, fears, depressed mood, cardiovascular and gastrointestinal symptoms appeared with mild anxiety levels while other symptoms like insomnia, somatic symptoms, autonomic symptoms, respiratory and genitourinary symptoms appeared with high severity levels. The presence of risk factors for anxiety among patients of diabetes predicts a causal relationship and deserves attention from clinicians

Role of contrast enhanced computed tomography in assessing cervical lymph node metastases in oral cavity squamous cell carcinoma

Objective: To evaluate the diagnostic accuracy of contrast-enhanced computed tomography scan in detecting cervical nodal metastasis in oral cavity squamous cell carcinoma.Methods: The retrospective cross-sectional study was conducted at Aga Khan University Hospital, Karachi, Pakistan. and comprised records from January 1, 2015, to October 31, 2016, of patients diagnosed with oral cavity squamous cell carcinoma and who underwent surgical resection of primary tumour along with neck dissection after having a contrast-enhanced computed tomography scan of head and neck. Diagnostic accuracy of the scans was calculated using final histopathology as the gold standard. All scans were reviewed by a consultant radiologist. Data was analysed using SPSS 23.Results: Of the 100 patients whose records were reviewed, 70(70%) were female, 55(55%) had buccal and 32(32%) had tongue cancer.. The scans had sensitivity 83%, specificity 61.7%, positive predictive value 70.9%, negative predictive value 76.3% and overall diagnostic accuracy 73%.Conclusions: Computed tomography scan was found to be a useful tool for preoperative staging of oral cavity squamous cell carcinoma. However, due to low specificity and negative predictive value, elective neck dissection should still be done in a negative scan for cervical lymph node metastases

The descriptive study of imposter syndrome in medical students

Background: Imposter syndrome is characterized by chronic feelings of self-doubt and fear of being discovered as an intellectual fraud. Despite evidence of abilities, those suffering from imposter syndrome are unable to internalize a sense of accomplishment, competence, or skill. Overall, they believe themselves to be less intelligent and competent than others perceive them to be. IS has several potential implications for medical education. The current study was designed to find out the frequency of imposter syndrome among medical students college so that certain measures must be taken to improve the teaching and learning methodologies as well as the curriculum.Methods: A cross-sectional, psycho-social analysis was conducted from March to July, 2018 at Nishtar Medical College, Multan after taking informed consent from the students. Clance Imposter Phenomenon Sclae (CIPS) was used to assess the prevalence and degree of severity of Imposter syndrome among medical chosen on basis of random sampling. The data collected was entered and analysed on SPSS v.20.Results: Two hundred (200) students were selected for the study and were asked to return the completed 20 items questionnaire. One hundred and eighty-nine (189) students returned the questionnaires, so the response rate was 94.5%. Out of 189 students, 121(64.36%) were males and 68(35.97%) were females. According to Clance imposter phenomenon scoring, of the total 189 students the severity of imposter syndrome is as follows: mild, 5(2.64%), moderate,72(38.09%), severe,103(54.49%) and very severe, 09(4.76%). Moreover, third year students were found to have high prevalence and degree of severity of imposter syndrome.Conclusions: Imposter phenomenon exists in a significant percentage of medical students and appears to peak in the third year of medical school. Both genders are at equal risk of having imposter syndrome. It is associated with various psychological illnesses. Further discussion regarding medical education paradigms in light of high levels of imposter phenomenon is needed

Insomnia among medical students: a cross-sectional study

Background: Insomnia, the most common sleep disorder, is the perception or complaint of inadequate or poor-quality sleep because of one or more of the following conditions: difficulty in falling asleep, frequent waking up during the night with difficulty for returning to sleep, waking up too early in the morning, or unrefreshing sleep. It is the most common sleep related complaint reported in the primary care setting. Medical students are specially at risk of developing insomnia and its consequences. This study evaluates the prevalence and severity of insomnia in medical students in relation to certain socio-demographic factors like age, sex and class of education.Methods: A questionnaire based study was done on 135 medical students of Nishtar Medical University, Multan chosen on basis of random sampling to test the prevalence of insomnia using Athens Insomnia Scale (AIS). Out of these students 75 were males and 60 were females. Students were interviewed to obtain information about age, sex and academic year of education.Results: According to Athens insomniac scale scoring, 55 (40.74%) students were found insomniac while 80 (59.25%) were non-insomniac. Out of 55 insomniac students, 23 (41.81%) were males while 32 (58.18%) were females. Likewise, out of 80 non-insomniac students, 52 (65%) were males while 28 (35%) were females. The prevalence of insomnia in medical students was found to be increased with the increasing age. It was found that the females have more insomnia prevalence as well as more severe signs and symptoms of insomnia. Moreover, final year students tend to show more prevalence and severity of insomnia than their juniors.Conclusions: According to this study, 2 out of every 5 students were insomniac. Demographic comparison showed that the prevalence and severity of insomnia was more in females and final year students. Also, it was increasing side by side with increasing age

Immunization status of students of Nishtar medical university against hepatitis B

Background: Hepatitis B virus (HBV) infection causes significant morbidity and mortality worldwide. Occupational exposure of health care workers and medical students increase their risk of acquiring HBV infection, and many authorities recommend vaccination. However, significant proportions of health care workers do not receive HBV immunization, and remain at increased risk to HBV infection. The present study was conducted on medical students to evaluate their knowledge regarding HBV and to know their vaccination status.Methods: This cross sectional, randomized, observational study was done at Nishtar medical university, Multan from November 2017 to July 2018. A pre-structured and tested questionnaire was given to 150 medical students from first year to final year. Out of these students 75 were males and 75 were females. The students were also interviewed about age, gender, year of study, screening before vaccination, history of vaccination, completion of all 3 doses and reasons for not getting vaccinated.Results: Out of 150 participants, 117 (78%) were vaccinated against HBV. In the vaccinated group, 90 (77%) completed all the three doses of their vaccination schedule and remaining 27 (23%) students were incompletely vaccinated. Rate of vaccine uptake was higher in females; 63 (84%) than in males: 53 (71%). Reasons of not being vaccinated were lack of knowledge about consequences (15.5%), casual behaviour (36%), not knowing from where to get vaccine (12%), fear of injection (10%), busy in studies (10%) and financial problems (8%). Prior screening was done in 74 (63%) students before the vaccination.Conclusions: Despite the availability and accessibility of a cost-effective hepatitis B vaccine since mid80's, the vaccination coverage among medical students is low. Health education needs to be improved in all medical students. The orientation and awareness programmes should be held to create awareness regarding HBV infection

Influence of the electrodeposition potential on the crystallographic structure and effective magnetic easy axis of cobalt nanowires

Cobalt nanowires (NWs) have been synthesized by electrodeposition inside the pores of anodized aluminium oxide templates, at different values of applied deposition potential. The as-deposited NWs are parallel to one another and exhibit a high geometrical aspect ratio. The crystal structure of these NWs shows a strong dependence on the applied deposition potential during synthesis. X-ray diffraction indicates the predominance of hexagonal-closed-packed (HCP) phase with (002) texture at low applied deposition potentials, whereas a reorientation of the c-axis of the HCP structure is observed for high electrodeposition potentials. Moreover, for a given electrodeposition time, the length of the NWs also increases with the applied potential. As a result of these structural changes, a switch in the magnetic easy axis, from parallel to perpendicular to the NWs axis, occurs depending on the applied potential. A simplified model is used to account for this reorientation of the effective magnetic anisotropy direction, which takes into account the interplay between shape anisotropy, magnetocrystalline anisotropy and interwire dipolar interactions