Two and one-dimensional honeycomb structures of silicon and germanium

Based on first-principles calculations of structure optimization, phonon modes and finite temperature molecular dynamics, we predict that silicon and germanium have stable, two-dimensional, low-buckled, honeycomb structures. Similar to graphene, they are ambipolar and their charge carriers can behave like a massless Dirac fermions due to their pi- and pi*-bands which are crossed linearly at the Fermi level. In addition to these fundamental properties, bare and hydrogen passivated nanoribbons of Si and Ge show remarkable electronic and magnetic properties, which are size and orientation dependent. These properties offer interesting alternatives for the engineering of diverse nanodevices.Comment: 4 pages, 3 figures and 1 table. (published in Physical Review Letters

Two and one-dimensional honeycomb structures of silicon and germanium

Based on first-principles calculations of structure optimization, phonon modes and finite temperature molecular dynamics, we predict that silicon and germanium have stable, two-dimensional, low-buckled, honeycomb structures. Similar to graphene, they are ambipolar and their charge carriers can behave like a massless Dirac fermions due to their pi- and pi*-bands which are crossed linearly at the Fermi level. In addition to these fundamental properties, bare and hydrogen passivated nanoribbons of Si and Ge show remarkable electronic and magnetic properties, which are size and orientation dependent. These properties offer interesting alternatives for the engineering of diverse nanodevices.Comment: 4 pages, 3 figures and 1 table. (published in Physical Review Letters

Time Dependence of Joint Entropy of Oscillating Quantum Systems

The time dependent entropy (or Leipnik's entropy) of harmonic and damped harmonic oscillator systems is studied by using time dependent wave function obtained by the Feynman path integral method. The Leipnik entropy and its envelope change as a function of time, angular frequency and damping factor. Our results for simple harmonic oscillator are in agreement with the literature. However, the joint entropy of damped harmonic oscillator shows remarkable discontinuity with time for certain values of damping factor. The envelope of the joint entropy curve increases with time monotonically. These results show the general properties of the envelope of the joint entropy curve for quantum systems

JOINT ENTROPY OF THE HARMONIC OSCILLATOR WITH TIME-DEPENDENT MASS AND/OR FREQUENCY

Time-dependent joint entropy is obtained for harmonic oscillator with the time-dependent mass and frequency case. It is calculated by using time-dependent wave function obtained via Feynman path integral method. Variation of time dependence is investigated for various cases

Modification of electronic structure, magnetic structure, and topological phase of bismuthene by point defects

Akturk, Ethem/0000-0002-1615-7841; Demirci, Salih/0000-0002-1272-9603WOS: 000418655400016This paper reveals how the electronic structure, magnetic structure, and topological phase of two-dimensional (2D), single-layer structures of bismuth are modified by point defects. We first showed that a free-standing, single-layer, hexagonal structure of bismuth, named h-bismuthene, exhibits nontrivial band topology. We then investigated interactions between single foreign adatoms and bismuthene structures, which comprise stability, bonding, electronic structure, and magnetic structures. Localized states in diverse locations of the band gap and resonant states in band continua of bismuthene are induced upon the adsorption of different adatoms, which modify electronic and magnetic properties. Specific adatoms result in reconstruction around the adsorption site. Single vacancies and divacancies can form readily in bismuthene structures and remain stable at high temperatures. Through rebondings, Stone-Whales-type defects are constructed by divacancies, which transform into a large hole at high temperature. Like adsorbed adatoms, vacancies induce also localized gap states, which can be eliminated through rebondings in divacancies. We also showed that not only the optical and magnetic properties, but also the topological features of pristine h-bismuthene can be modified by point defects. The modification of the topological features depends on the energies of localized states and also on the strength of coupling between point defects.TUBA, Turkish Academy of Sciences (Turkey); Research Fund of Adnan Menderes University (Turkey) [MF-16004]The computational resources are provided by TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure). S.C. acknowledge financial support from TUBA, Turkish Academy of Sciences (Turkey). This research was supported by Research Fund of Adnan Menderes University (Turkey), Project No. MF-16004. We thank Dominik Gresch for helpful discussions on operating Z2-PACK

Proprotein convertase subtilisin/kexin type 9 (PCSK9), soluble lectin-like oxidized LDL receptor 1 (sLOX-1) and ankle brachial index in patients with differentiated thyroid cancer.

The cardiovascular effects of short-term overt hypothyroidism are not well known. We investigated proprotein convertase subtilisin/kexin type 9 (PCSK9), soluble lectin-like oxidized LDL receptor 1 (sLOX-1) and the ankle brachial index (ABI) in thyroid cancer patients with short-term overt hypothyroidism due to thyroid hormone withdrawal (THW). Twenty-one patients requiring radioactive iodine (RAI) ablation or scanning and 36 healthy control subjects were enrolled. Patients were evaluated in the subclinical thyrotoxic phase when they were on suppressive levothyroxine therapy and in the overt hypothyroid phase due to THW for four weeks. PCSK9, sLOX-1, lipids and ABI were measured in the patient and control groups. Total cholesterol, LDL cholesterol, triglycerides and Apo B levels were increased in short overt hypothyroidism compared with the control group (p<0.001). PCSK9 levels increased before THW and after THW in the patients compared to control group (p<0.001, p=0.004, respectively). sLOX-1 levels were not different between patients with short term overt hypothyroidism and control group (p=0.27). ABI was found to be significantly decreased in patients with thyroid cancer before and after THW compared to control group (p=0.04, p=0.002 respectively). PCSK9 levels were correlated negatively with ABI (r=-0.38, p=0.004). In conclusion; our study demonstrated that patients with differentiated thyroid cancer both before and after THW which is a short term overt hypothyroid phase, had increased PCSK9 levels and decreased ABI. Short term overt hypothyroidism also leads to increased HDL, LDL, total cholesterol, Apo A and Apo B levels

Proprotein convertase subtilisin/kexin type 9 (PCSK9), soluble lectin-like oxidized LDL receptor 1 (sLOX-1) and ankle brachial index in patients with differentiated thyroid cancer

The cardiovascular effects of short-term overt hypothyroidism are not well known. We investigated proprotein convertase subtilisin/kexin type 9 (PCSK9), soluble lectin-like oxidized LDL receptor 1 (sLOX-1) and the ankle brachial index (ABI) in thyroid cancer patients with short-term overt hypothyroidism due to thyroid hormone withdrawal (THW). Twenty-one patients requiring radioactive iodine (RAT) ablation or scanning and 36 healthy control subjects were enrolled. Patients were evaluated in the subclinical thyrotoxic phase when they were on suppressive levothyroxine therapy and in the overt hypothyroid phase due to THW for four weeks. PCSK9, sLOX-1, lipids and ABI were measured in the patient and control groups. Total cholesterol, LDL cholesterol, triglycerides and Apo B levels were increased in short overt hypothyroidism compared with the control group (p<0.001). PCSK9 levels increased before THW and after THW in the patients compared to control group (p<0.001, p=0.004, respectively). sLOX-1 levels were not different between patients with short term overt hypothyroidism and control group (p=0.27). ABI was found to be significantly decreased in patients with thyroid cancer before and after THW compared to control group (p=0.04, p=0.002 respectively). PCSK9 levels were correlated negatively with ABI (r=-0.38, p=0.004). In conclusion; our study demonstrated that patients with differentiated thyroid cancer both before and after THW which is a short term overt hypothyroid phase, had increased PCSK9 levels and decreased ABI. Short term overt hypothyroidism also leads to increased HDL, LDL, total cholesterol, Apo A and Apo B levels

Serum Total Sialic Acid Level is Elevated in Hypothyroid Patients as an Atherosclerotic Risk Factor

BackgroundSerum total sialic acid (TSA) concentration is regarded as an indicator of the risks of atherosclerosis and cardiovascular diseases. The association between SA levels and atherosclerosis risk factors has not been assessed in patients with thyroid diseases. MethodsSixty newly diagnosed treatment-naive hypothyroid patients, 35 with subclinical and 25 with overt hypothyroidism, and 30 euthyroid individuals were analyzed. SA was measured in fasting blood samples, as were routine biochemical parameters, some atherosclerosis markers and carotid artery intima media thickness (CIMT). ResultsMean SA (38.1 12.0 vs. 46.0 +/- 15.8; P = 0.019) and CIMT (0.57 +/- 0.06 vs. 0.62 +/- 0.12; P = 0.013) were found to be higher in the patient group compared with the control group. Mean sialic acid was higher in overt hypothyroidism patients compared with subclinical hypothyroidism patients and the control group. No difference was found between the subclinical hypothyroidism group and the control group. Sialic acid level and CIMT had a positive correlation in both the entire population and the hypothyroidism group. The linear regression model established for mean CIMT level in the entire population showed that risk factors of LDL (B +/- SE = 0.454 +/- 0.206; P = 0.030), uric acid (B +/- SE = 1.902 +/- 0.686; P = 0.007), hs-CRP (B +/- SE = 1.003 +/- 0.380; P =0.010), and SA (B +/- SE = 2.419 +/- 0.450; P < 0.001) were independent predictors of CIMT level. ConclusionSialic acid level is elevated in hypothyroid patients. However, this elevation is not related to thyroid hormone levels and autoantibodies. Correlations between SA and atherosclerosis indicators, such as CIMT, LDL, hs-CRP, and uric acid, in hypothyroid individuals suggest that SA may be an indicator of atherogenesis in these patients

Guided intraoperative scintigraphic tumor targeting of metastatic cervical lymph nodes in patients with differentiated thyroid cancer: a single-center report

Objective: Our aim was to present our experiences related to performing neck surgery using the guided intraoperative scintigraphic tumor targeting (GOSTT) procedure for patients who had locally recurrent or persistent differentiated thyroid cancer (DTC) and who had undergone previous thyroid surgery. Subjects and methods: We retrospectively evaluated 11 patients who had locally recurrent or persistent DTC, who had undergone previous surgery, and for whom reoperation was planned for metastatic cervical lymph nodes (LNs). We performed the neck surgery using the GOSTT procedure on all patients and at a single academic institution. Results: The 11 patients had a total of 26 LNs, as marked with a radiotracer, and those LNs' mean size was 14.7 +/- 8.2 mm (range: 5-34 mm). Histopathological examinations revealed DTC metastasis in all 26 of the preoperatively marked LNs. Of the 11 patients, only one needed a reoperation in the neck; she had another successful surgery (also using the GOSTT procedure). In the evaluation of the patients' final status, all were disease-free in their necks. There also were no GOSTT-associated postoperative complications. Conclusion: The GOSTT procedure is a useful, successful, inexpensive, and comfortable procedure for marking and mapping metastatic LNs, especially in DTC patients who have undergone previous surgery