Comparison of the formulations for a hub-and-spoke network design problem under congestion

In this paper, we study the hub location problem with a power-law congestion cost and propose an exact solution approach. We formulate this problem in a conic quadratic form and use a strengthening method which rests on valid inequalities of perspective cuts in mixed integer nonlinear programming. In a numerical study, we compare two well known types of mathematical modeling in the hub-location problems which are solved with different branch and cut strategies. The strength and weakness of the formulations are summarized based on an extensive numerical study over the CAB data set

Electric Switching of the Charge-Density-Wave and Normal Metallic Phases in Tantalum Disulfide Thin-Film Devices

We report on switching among three charge-density-wave phases - commensurate, nearly commensurate, incommensurate - and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced by application of an in-plane electric field. The electric switching among all phases has been achieved over a wide temperature range, from 77 K to 400 K. The low-frequency electronic noise spectroscopy has been used as an effective tool for monitoring the transitions, particularly the switching from the incommensurate charge-density-wave phase to the normal metal phase. The noise spectral density exhibits sharp increases at the phase transition points, which correspond to the step-like changes in resistivity. Assignment of the phases is consistent with low-field resistivity measurements over the temperature range from 77 K to 600 K. Analysis of the experimental data and calculations of heat dissipation suggest that Joule heating plays a dominant role in the electric-field induced transitions in the tested 1T-TaS2 devices on Si/SiO2 substrates. The possibility of electrical switching among four different phases of 1T-TaS2 is a promising step toward nanoscale device applications. The results also demonstrate the potential of noise spectroscopy for investigating and identifying phase transitions in materials.Comment: 32 pages, 7 figure

Spin - Phonon Coupling in Nickel Oxide Determined from Ultraviolet Raman Spectroscopy

Nickel oxide (NiO) has been studied extensively for various applications ranging from electrochemistry to solar cells [1,2]. In recent years, NiO attracted much attention as an antiferromagnetic (AF) insulator material for spintronic devices [3-10]. Understanding the spin - phonon coupling in NiO is a key to its functionalization, and enabling AF spintronics' promise of ultra-high-speed and low-power dissipation [11,12]. However, despite its status as an exemplary AF insulator and a benchmark material for the study of correlated electron systems, little is known about the spin - phonon interaction, and the associated energy dissipation channel, in NiO. In addition, there is a long-standing controversy over the large discrepancies between the experimental and theoretical values for the electron, phonon, and magnon energies in NiO [13-23]. This gap in knowledge is explained by NiO optical selection rules, high Neel temperature and dominance of the magnon band in the visible Raman spectrum, which precludes a conventional approach for investigating such interaction. Here we show that by using ultraviolet (UV) Raman spectroscopy one can extract the spin - phonon coupling coefficients in NiO. We established that unlike in other materials, the spins of Ni atoms interact more strongly with the longitudinal optical (LO) phonons than with the transverse optical (TO) phonons, and produce opposite effects on the phonon energies. The peculiarities of the spin - phonon coupling are consistent with the trends given by density functional theory calculations. The obtained results shed light on the nature of the spin - phonon coupling in AF insulators and may help in developing innovative spintronic devices.Comment: 16 pages; 2 figure

Prevalence and risk factors of complication of endotracheal extubation in teaching hospitals affiliated with Jahrom University of medical science

Endotracheal intubation is to maintain a safe open airway to prevent pulmonary aspiration by administrating general anesthesia. Endotracheal tube, as a foreign body, can stimulate the patients’ airway during the emergence from general anesthesia and cause various reactions and complications immediately or within a multi-day delay.The present study intended to determine the prevalence and associated risk factors of the complications of endotracheal extubation (removal of endotracheal tube / ETT) within 24 hrs. since the surgery. To this end, a descriptive research was conducted on 200 adult candidates for elective and emergency surgery of endotracheal intubation by administrating general anesthesia. Data about the intended associated risk factors and complications were respectively collected in operating room (OR) and within 24 hrs. since surgery and were recorded in the questionnaire. The results indicated that the prevalent complications were sore throat (%21), cough (%12.5) and hoarseness (%15.5). There was not any case of dysphagia and bloody sputum (blood-streaked expectorant). Also, there was a significant relationship between sore throat and the type of surgery (P˂0.001). On the other hand, there was not any statistically significant relationship between sore throat and other associated risk factors (sex, age, weight, type of surgery and size of endotracheal tube). Likewise, not any significant relationship was observed between cough, hoarseness and the intended risk factors. To conclude, the present study found that the type of surgery has a significant effect on the incidence of sore throat within 24 hrs. since the surgical operation; thus, raising awareness of these risk factors and taking proper actions, particularly during intubation, can reduce the incidence of complications, in particular sore throat, and improve patients’ satisfaction.Keywords: General Anesthesia; Intubation; Complication

Comparison of complications of spinal and general anesthasia in percutaneous kidney stone removal

While the complications of spinal anesthesia are much less than general anesthesia, percutaneous nephrolithotomy (PCNL) is still performed under general anesthesia in most centers. Therefore, in this study spinal anesthesia is compared with general anesthesia in patients undergoing PCNL. This research was a double-blind clinical trial study which was conducted on 130 patients with inclusion criteria. Patients were nonrandomly assigned into two general anesthesia (n=65) and spinal anesthesia (n=65) groups and underwent PCNL surgery.In group A, patients were given intravenously midazolam (2 mg), fentanyl (100 μg), atracurium (0.5 mg/kg), propofol (2 mg/kg) and morphine (10 mg) and then were incubated. In group B, Marcaine 0.5% (15 mg) was injected into the L3-L4 or L4-L5 lumbar spinal space in a sitting position. Patient’s blood pressure was measured and recorded at various times and in recovery as well as in the surgery room. Intra-operative bleeding, pain in the surgery area, nausea and vomiting, shortness of breath and sore throat were recorded for the two groups in the ward and during hospitalization.Changes of blood pressure were the same in both groups. In the general anesthesia group, intra-operative bleeding, pain at the site of the surgery, nausea and vomiting, shortness of breath and sore throat and duration of hospitalization were significantly higher. Changes in other tests were equal in both groups. Spinal anesthesia might be a safer method than general anesthesia for PCNL surgery.Keywords: Complication, Spinal Anesthesia, General Anesthesia, Kidney Stone Removal, Percutaneou

Phonon and Thermal Properties of Quasi-Two-Dimensional FePS3 and MnPS3 Antiferromagnetic Semiconductor Materials

We report results of investigation of the phonon and thermal properties of the exfoliated films of layered single crystals of antiferromagnetic FePS3 and MnPS3 semiconductors. The Raman spectroscopy was conducted using three different excitation lasers with the wavelengths of 325 nm (UV), 488 nm (blue), and 633 nm (red). The resonant UV-Raman spectroscopy reveals new spectral features, which are not detectable via visible Raman light scattering. The thermal conductivity of FePS3 and MnPS3 thin films was measured by two different techniques: the steady-state Raman optothermal and transient time-resolved magneto-optical Kerr effect. The Raman optothermal measurements provided the orientation-average thermal conductivity of FePS3 to be 1.35 W/mK at room temperature. The transient measurements revealed that the through-plane and in-plane thermal conductivity of FePS3 is 0.85 W/mK and 2.7 W/mK, respectively. The films of MnPS3 have higher thermal conductivity of 1.1 W/mK through-plane and 6.3 W/mK in-plane. The data obtained by both techniques reveal strong thermal anisotropy of the films and the dominant contribution of phonons to heat conduction. Our results are important for the proposed applications of the antiferromagnetic semiconductor thin films in spintronic devices.Comment: 43 pages, 8 figure

Specifics of the Elemental Excitations in "True One-Dimensional" MoI3_3 van der Waals Nanowires

We report on the temperature evolution of the polarization-dependent Raman spectrum of exfoliated MoI$_3$, a van der Waals material with a "true one-dimensional" crystal structure that can be exfoliated to individual atomic chains. The temperature evolution of several Raman features reveals anomalous behavior suggesting a phase transition of a magnetic origin. Theoretical considerations indicate that MoI$_3$ is an easy-plane antiferromagnet with alternating spins along the dimerized chains and with inter-chain helical spin ordering. The calculated frequencies of the phonons and magnons are consistent with the interpretation of the experimental Raman data. The obtained results shed light on the specifics of the phononic and magnonic states in MoI$_3$ and provide a strong motivation for future study of this unique material with potential for spintronic device applications.Comment: 28 page