Best practices for HPM-assisted performance engineering on modern multicore processors

Many tools and libraries employ hardware performance monitoring (HPM) on modern processors, and using this data for performance assessment and as a starting point for code optimizations is very popular. However, such data is only useful if it is interpreted with care, and if the right metrics are chosen for the right purpose. We demonstrate the sensible use of hardware performance counters in the context of a structured performance engineering approach for applications in computational science. Typical performance patterns and their respective metric signatures are defined, and some of them are illustrated using case studies. Although these generic concepts do not depend on specific tools or environments, we restrict ourselves to modern x86-based multicore processors and use the likwid-perfctr tool under the Linux OS.Comment: 10 pages, 2 figure

Mechanical, Corrosive, and Tribological Degradation of Metal Coatings and Modified Metallic Surfaces

Mechanical, corrosive, and tribological degradation of metal and metal coatings is just one of the challenges faced by numerous industries [...

Unravelling the Role of Nitrogen in Surface Chemistry and Oxidation Evolution of Deep Cryogenic Treated High-Alloyed Ferrous Alloy

The role of nitrogen, introduced by deep cryogenic treatment (DCT), has been investigated and unraveled in relation to induced surface chemistry changes and improved corrosion resistance of high-alloyed ferrous alloy AISI M35. The assumptions and observations of the role of nitrogen were investigated and confirmed by using a multitude of complementary investigation techniques with a strong emphasis on ToF-SIMS. DCT samples display modified thickness, composition and layering structure of the corrosion products and passive film compared to a conventionally heat-treated sample under the same environmental conditions. The changes in the passive film composition of a DCT sample is correlated to the presence of the so-called ghost layer, which has higher concentration of nitrogen. This layer acts as a precursor for the formation of green rust on which magnetite is formed. This specific layer combination acts as an effective protective barrier against material degradation. The dynamics of oxide layer build-up is also changed by DCT, which is elucidated by the detection of different metallic ions and their modified distribution over surface thickness compared to its CHT counterpart. Newly observed passive film induced by DCT successfully overcomes the testing conditions in more extreme environments such as high temperature and vibrations, which additionally confirms the improved corrosion resistance of DCT treated high-alloyed ferrous alloys

Leading Through Educational Distress: An Autoethnography of the Journey of a School Administrator

The purpose of this autoethnography is to provide analysis of personal leadership experiences during times of educational distress in order to extend understanding of the nuances of educational leadership for new and experienced leaders. An autoethnography is a qualitative research method in which the researcher is also the subject of the study. When looking at cultural groups or events, quantitative research methods do not translate to the meanings of humans in social interaction or speak to the significance of human thought and action (Adams, Holman Jones, & Ellis, 2015). In autoethnography, the researcher uses autobiographical stories to analyze and interpret their lived experiences with the purpose of extending sociological understanding. It reflects the interconnectivity of self, others and culture (Hamdan, 2012). This autoethnography utilizes a leadership framework as an analysis of learning and growth of the leader during two specific events of educational distress. The six domains of the leadership frame are: relational, collaborative, systems, visionary, instructional, and servant. A person cannot predict when an educational distressing event will occur. To lead during times of educational distress, it is important to have a strong understanding of your leadership framework and personal beliefs

“Who has a right to say what focus is the legitimate focus?” Tennessee Williams and Julia Margaret Cameron’s Theatrical Portraits of Women

In the production notes preceding The Glass Menagerie, Tennessee Williams said: “Everyone should know nowadays the unimportance of the photographic in art: that truth, life, or reality is an organic thing which the poetic imagination can represent or suggest, in essence, only through transformation, through changing into other forms than those which were merely present in appearance.” In spite of Williams’s emphasis on the limitations of literal representation, some of his most famous female characters were created in a tradition similar to that of portraits of women by the Victorian-era photographer Julia Margaret Cameron. Both Cameron and Williams made portraits of women that encouraged an understanding of and allowance for multiple truths. This thesis explores the parallels between Williams’s theatrical “portraits” and Cameron’s “theatrical” portraits, and demonstrates that both artists empowered women characters with the ability to perform truth that is much larger than (and frequently contradicts) that which is “merely present in appearance.” This discussion examines the visual techniques that Cameron used in her portrait photographs in order to illuminate the ways Williams built similar performances in his scripts, and then tracks women characters from four of Williams’s plays— “Portrait of a Madonna,” A Streetcar Named Desire, Cat on a Hot Tin Roof, and Sweet Bird of Youth—tracing a progression of their power through their dialogue, Williams’s stage directions, and his writings about the characters and plays

Synthesis and characterization of sterically and electronically tuned ligands toward magnetic control of iron and cobalt complexes

2015 Spring.Includes bibliographical references.Presented within this dissertation are the syntheses and characterizations of iron and cobalt complexes featuring ligands designed to tune the magnetic properties. Two key magnetic phenomena are of interest: spin crossover and single-molecule magnetism. Both of these topics are known to be significantly influenced by subtle changes in coordination and inter- and intramolecular interactions. The overarching goal is to understand how the magnetic properties of the metal center can be controlled via electronic and steric modifications. In Chapter 1, I offer a brief introduction into the background and motivation of the works presented in this dissertation in the realm of spin crossover and single-molecule magnetism. The first section of this chapter is focused on spin crossover and how host:guest interactions can be exploited to alter the magnetic behavior of first-row transition metals. Examples of Fe(II) complexes that display anion-dependent spin state behaviors in both the solid-state and in solution are discussed. Functionalized tripodal Schiff-base ligands are placed into context as an extension of previous research into tripodal ligands for use as metal-based anion-receptors and tripodal spin crossover complexes. The second section of Chapter 1 gives a brief introduction into single-molecule magnetism. An examination of mononuclear Co(II) complexes displaying slow magnetic relaxation and application of acetylide-bridged metal centers to enhance magnetic communication are also given. In Chapter 2, I discuss the preparation and characterizations of a Fe(II) complex coordinated by the alcohol functionalized hexadentate tripodal iminopyridine L6-OH with varying anions. Solid-state magnetic susceptibility measurements of [FeL6-OH]X2 (X = OTf-, Br-, I-, or BPh4-) reveal an anion-dependence on the magnetic behavior. Magnetostructural correlations indicate that stronger hydrogen-bonding interactions are achieved with larger anions, which are better able to undergo bifurcated interactions with the hydroxyl groups from two of the arms. Removal of the tether between the ligand arms leads to the formation of [Fe(L2)2](OTf)2, a bis(tridentate) complex that remains high spin at all temperatures. Variable temperature magnetic measurements in d3-methanol reveal that the high spin state of [FeL6-OH]2+ persists regardless of the anion down to 183 K. In Chapter 3, attempts towards synthesizing the heteroarmed tris(imine) [FeL556]2+ and analogous bis(imine)-mono(amine) [FeL556-NH]2+ complexes are discussed. Several routes are attempted to synthesize the tris-iminopyridine species including selective deprotonation of tris(2-aminoethyl)amine*3 HCl, in situ complex formation via metal-templated self-assembly, and use of presynthesized ligands. Analyses of the reaction mixtures by mass spectrometry suggest that mixtures of products are formed regardless of the method. An anion and solvent dependence leads to preferential formation of the low-spin species [FeL5-ONHtBu]2+, while using solvents such as acetonitrile and ethanol lead to increased production of the desired [FeL556]2+. To test if anion-dependent magnetic behavior can be observed with this ligand type, the comparable complex [FeL556-NH]2+ was synthesized and characterized. Variable temperature solution measurements in d3-acetonitirile suggest that host:guest interactions in solution induce a stabilization of the low-spin state for [FeL556-NH]2+ as indicated by a decrease in susceptibility at lower temperatures for the Cl- salt. In Chapter 4, the preparation, structural, and magnetic characterizations for a family of Fe(II) complexes of tripodal ligands based on L5-ONHtBu are presented. The series of ligands aim to tune the ligand field by selectively reducing imines to amines, producing the ligands L5-(NH)x (x = 1 - 3, number of amines). In the solid state, the three Fe(II) complexes formed are high spin, but significant differences in the structural distortion of both the coordination environment of the Fe(II) center as well as the anion-binding pocket of the amides are noted. In solution, the complexes [FeL5-(NH)3]2+ and [FeL5-NH]2+ are high spin between 183 and 308 K in d6-acetone but interestingly, [FeL5-(NH)2]2+ undergoes a spin-state change with decreasing temperature. Variable temperature studies in d6-acetone and anion titrations in d3-acetonitrile at room temperature monitored by Evans' method of [FeL5-(NH)2]2+ show host:guest interactions stabilize the high spin state. These studies suggest a viable method of ligand tuning for spin-state control by host:guest interactions. In Chapter 5, I discuss the structural and magnetic properties of [Co5-ONHtBu]X2 (X = Cl-, Br-, I-, and ClO4-). These hexadentate Co(II) complexes vary only in the charge-balancing anion, but marked differences in their magnetic properties are observed. Investigation of the magnetic anisotropy of the various salts reveal that the chloride salt possesses the most axial anisotropy, which manifests as an exhibition of slow magnetic relaxation under application of an external field. To my knowledge this is the first example of anion-binding influencing the magnetic anisotropy and 'turning on' single-molecule magnet-like behavior. Lastly, Chapter 6 describes the syntheses and magnetic properties of a series of mono-and dinuclear Fe(III) complexes bridged by ethynylmesitylene ligands. Inclusion of steric bulk onto the bridging-aryl ligand is predicted to increase orbital overlap between the singly-occupied molecular orbital of the metal center and the π-system of the aryl linker. The addition of methyl groups to the aryl ring cements the desired equatorial ligand orientation with respect to the π-system. This leads to an increase in ferromagnetic coupling between the metal centers

Concordance of surfaces in 4-manifolds and the Freedman–Quinn invariant

We prove a concordance version of the 4-dimensional light bulb theorem for $\pi_1$-negligible compact orientable surfaces, where there is a framed but not necessarily embedded dual sphere. That is, we show that if $F_0$ and $F_1$ are such surfaces in a 4-manifold $X$ that are homotopic and there exists an immersed framed 2-sphere $G$ in $X$ intersecting $F_0$ geometrically once, then $F_0$ and $F_1$ are concordant if and only if their Freedman-Quinn invariant $\mathop{fq}$ vanishes. The proof of the main result involves computing $\mathop{fq}$ in terms of intersections in the universal covering space and then applying work of Sunukjian in the simply-connected case