Graphene-Dielectric Composite Metamaterials: Evolution from Elliptic to Hyperbolic Wavevector Dispersion and The Transverse Epsilon-Near-Zero Condition

We investigated a multilayer graphene-dielectric composite material, comprising graphene sheets separated by subwavelength-thick dielectric spacer, and found it to exhibit hyperbolic isofrequency wavevector dispersion at far- and mid-infrared frequencies allowing propagation of waves that would be otherwise evanescent in a dielectric. Electrostatic biasing was considered for tunable and controllable transition from hyperbolic to elliptic dispersion. We explored the validity and limitation of the effective medium approximation (EMA) for modeling wave propagation and cutoff of the propagating spatial spectrum due to the Brillouin zone edge. We found that EMA is capable of predicting the transition of the isofrequency dispersion diagram under certain conditions. The graphene-based composite material allows propagation of backward waves under the hyperbolic dispersion regime and of forward waves under the elliptic regime. Transition from hyperbolic to elliptic dispersion regimes is governed by the transverse epsilon-near-zero (TENZ) condition, which implies a flatter and wider propagating spectrum with higher attenuation, when compared to the hyperbolic regime. We also investigate the tunable transparency of the multilayer at that condition in contrast to other materials exhibiting ENZ phenomena.Comment: to be published in Journal of Nanophotonic

Rough Cilicia Archaeological Survey: Report of the 2007 Season

The 2007 season of the Rough Cilicia Archaeological Survey Project was directed by Nicholas Rauh of Purdue University. Dr. Hulya Caner of the Institute for Marine Science Management at Istanbul University supervised the work of our highland pollen trench excavations. Dr. Unal Akkemik of the Department of Forest Botany, School of Forestry, at Istanbul University conducted the dendrochronological research. These scholars were assisted by graduate student, Margaret Bloome, of Arizona University, and undergraduate students Phillip Ramirez (Purdue University), Aaron Fettgather (American University), Alexander Jillions (American University) and Charlotte Rose (Brown University). Due to permit complications the field season lasted one week, August 2-9, 2007. This season the team focused on paleo-environmental research in the Biçkici Highland behind Gazipasha. Our purpose was to obtain data to determine the age of the current cedar forest near the tree line of the Tauros Mts. as well as to obtain pollen data from trench excavations at the same elevation to determine the remote history of the forest. At the highland (yayla) village of Sügözü, the team, supervised by Hulya Caner, excavated an open pit to obtain 50 soil samples of remarkably remote age. Unal Akkemik was able to obtain 15 tree ring samples from old growth cedar, black pine, and juniper trees in the vicinity to demonstrate that the current highland forest cover is relatively young

Integer Programming Formulations and Cutting Plane Algorithms for the Maximum Selective Tree Problem

This paper considers the Maximum Selective Tree Problem (MSelTP) as a generalization of the Maximum Induced Tree problem. Given an undirected graph with a partition of its vertex set into clusters, MSelTP aims to choose the maximum number of vertices such that at most one vertex per cluster is selected and the graph induced by the selected vertices is a tree. To the best of our knowledge, MSelTP has not been studied before although several related optimization problems have been investigated in the literature. We propose two mixed integer programming formulations for MSelTP; one based on connectivity constraints, the other based on cycle elimination constraints. In addition, we develop two exact cutting plane procedures to solve the problem to optimality. On graphs with up to 25 clusters, up to 250 vertices, and varying densities, we conduct computational experiments to compare the results of two solution procedures with solving a compact integer programming formulation of MSelTP. Our experiments indicate that the algorithm CPAXnY outperforms the other procedures overall except for graphs with low density and large cluster size, and that the algorithm CPAX yields better results in terms of the average time of instances optimally solved and the overall average time

A Material Perspective on Consequence of Deformation Heating During Stamping of DP Steels

Recent studies showed that, during stamping of high strength steels at industrially relevant production rates, local temperature in the blank may rise up to 200°C – 300°C due to deformation heating. Moreover, die temperature may also rise up to 100°C – 150°C for progressive stamping dies. Based on the common assumption that the blank softens as the temperature increases, thermal softening creates a margin in Forming Limit Diagram (FLD) and therefore the FLD determined at room temperature can safely be used for those cases. In this article, the validity of this assumption on DP590 steel is questioned by high temperature tensile tests (RT - 300°C) at various strain rates (10-3 s-1 – 1 s-1). The results indicated a decrease both in uniform and total elongation in 200°C – 300°C range together with several other symptoms of Dynamic Strain Aging (DSA) at all strain rates. Concurrent with the DSA, the simulated FLD confirms the lower formability at high temperature and strain rates. Thus, it is concluded FLD determined at RT may not be valid for the investigated steels

Rough Cilicia Archaeological Survey Project: Report of the 2004 Season

The priorities the season 2004 were to complete the envisioned maritime, geoarchaeological, and architectural surveys that had been organized for this particular grant cycle. Owing to the complexity of the 2004 season\u27s program, the various team components worked within a staggered schedule: the maritime and geoarchaeological surveys went first, followed by the architectural survey. The pedestrian survey basically worked to accommodate the needs of the other teams by working in and around them. Despite these limitations, the pedestrian team managed to conduct several days of \u27prospective\u27 survey in the Kaledran Canyon. The results of each of the team\u27s efforts are presented report in the sequence in which they occurred, maritime, geoarchaeological, architectural, and pedestrian

Robot-Assisted Laparoscopic Dismembered Pyeloplasty

OBJECTIVE: Advanced laparoscopic skills limit the implementation of laparoscopic pyeloplasty to centers with extensive experience. The introduction of robotic technology into the field of minimally invasive surgery has facilitated complex surgical dissection and genitourinary reconstruction. We report our experience with robot-assisted laparoscopic pyeloplasty using the da Vinci Robotic Surgical System at 3 New York City medical centers. METHODS: A review of all robot-assisted laparoscopic Anderson-Hynes dismembered pyeloplasty cases in 38 patients (21 females, 17 males) between April 2001 and January 2004 was performed. All patients had symptoms or radiographic evidence of ureteropelvic junction obstruction. Robotic assistance with the da Vinci Robotic Surgical System was used after preparation of the ureteropelvic junction with a standard laparoscopic approach. RESULTS: The average patient age was 39.3 years (range, 15 to 69). The mean operative time and suturing time were 225.6+/-59.3 minutes and 64.2+/-14.6 minutes. The average estimated blood loss was minimal at 77.3+/-55.3 mL. The mean length of hospitalization was 69.6 hours (range, 28 to 310). The average use of intravenous morphine was 26.5 mg (range, 0 to 162). No intraoperative complications occurred, and open conversions were not necessary. A mean follow-up of 12.2 months revealed a success rate of 94.7% with 2/38 patients requiring further treatments. CONCLUSIONS: This combined multi-institutional series reveals that robot-assisted pyeloplasty with the da Vinci Surgical System is safe and reproducible. These intermediate results appear comparable to results with open and laparoscopic pyeloplasty repairs

Rough Cilicia Archaeological Survey Project: Report of the 2002 Season

The Rough Cilicia Archaeological Project conducted archaeological and geoarchaeological research in the Gazipaşa area from July 20 through 1 September 2001. Several goals were met this season. Under the direction of Michael Hoff and Rhys Townsend, detailed plans were completed of monumental structures at the sites of Asar Tepe, Lamos, and Selinus. At Lamos, in particular, the team made a number of finds, including the discovery of an inscribed statue base of large size in a small podium complex on a hill above the so-called stadium

Automation of flexible handling of hot forged Tailored Forming components

Universalgreifer sind flexibel einsetzbar und können sich an verschiedene Situationen und Objekte anpassen. Aktuelle formvariable Universalgreifer bestehen überwiegend aus monolithischen polymeren Werkstoffen, deren maximale Einsatztemperaturen bei 300 °C liegen. Somit kann von der Formflexibilität nicht in Bereich profitiert werden in denen höhere Temperaturen vorherrschen und die zu handhabenden Objekte Umformungsprozesse durchschreiten. Solch ein Bereich ist der Schmiedesektor, bei dem die Objekte Temperaturen von bis zu 1250 °C erreichen. Die vorliegende Diskrepanz zwischen der Formvariabilität der Greifer und den Prozesstemperaturen im Schmiedesektor versuchen wir zu schließen. In dieser Arbeit stellen wir das von uns entwickelte Konzept eines formvariablen hochtemperaturbeständigem Handhabungssystem und deren praktische Umsetzung vor, sowie die noch zu lösenden Herausforderungen.Universal grippers are flexible and can adapt to different situations and objects. The shape variability has limitations, for example, the temperature. For manufacturing such shape variable grippers, elastic polymer materials are used. The material has an upper limit of the operating temperature of 300 °C. In the forging sector, the manufactured object change their geometry during the process and reaches temperature up 1250 °C. Here, we see the potential of the utilization of shape variable grippers. Therefore, we developed a system that overcomes the gap between the temperature limitation of current shape variable grippers and the high temperature in forging environments. This paper presents our gripper and the task to be solved in future works

Elevated arginine levels in liver tumors promote metabolic reprogramming and tumor growth

Arginine auxotropy, due to reduced expression of urea cycle genes, is common in cancer. However, little is known about the levels of arginine in these cancers. Here, we report that arginine levels are elevated in hepatocellular carcinoma (HCC) despite reduced expression of urea cycle enzymes. Liver tumors accumulate high levels specifically of arginine via increased uptake and, more importantly, via suppression of arginine-to-polyamine conversion due to reduced arginase 1 (ARG1) and agmatinase (AGMAT) expression. Furthermore, the high levels of arginine are required for tumor growth. Mechanistically, high levels of arginine promote tumorigenesis via transcriptional regulation of metabolic genes, including upregulation of asparagine synthetase (ASNS). ASNS-derived asparagine further enhances arginine uptake, creating a positive feedback loop to sustain high arginine levels and oncogenic metabolism. Thus, arginine is a novel second messenger-like molecule that reprograms metabolism to promote tumor growth