Measurement of Untruncated Nuclear Spin Interactions via Zero- to Ultra-Low-Field Nuclear Magnetic Resonance

Zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultra-low-field NMR measurements of residual dipolar couplings in acetonitrile-2-$^{13}$C aligned in stretched polyvinyl acetate gels. This represents the first investigation of dipolar couplings as a perturbation on the indirect spin-spin $J$-coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultra-low-field NMR and has potential applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.Comment: 6 pages, 3 figure

The Galois Complexity of Graph Drawing: Why Numerical Solutions are Ubiquitous for Force-Directed, Spectral, and Circle Packing Drawings

Many well-known graph drawing techniques, including force directed drawings, spectral graph layouts, multidimensional scaling, and circle packings, have algebraic formulations. However, practical methods for producing such drawings ubiquitously use iterative numerical approximations rather than constructing and then solving algebraic expressions representing their exact solutions. To explain this phenomenon, we use Galois theory to show that many variants of these problems have solutions that cannot be expressed by nested radicals or nested roots of low-degree polynomials. Hence, such solutions cannot be computed exactly even in extended computational models that include such operations.Comment: Graph Drawing 201

Innovative Technique of Vascular Repair in Intra-Operative IVC Rupture During Lumbar Microdiscectomy: A Case Report

Background: Major vascular injury during a spinal surgery is a rare but most dreaded complication. Case Presentation: A 39 years old female undergoing microscopic lumbar discectomy suddenly developed severe hypotension on table. The procedure was abandoned and the patient turned supine. It was diagnosed to be a major vessel tear and the patient was taken up for immediate successful vascular repair. To best of our knowledge such a repair procedure has not been described in literature. Conclusions: Majority of such vascular injuries are dealt with primary repair of the defect by a vascular surgeon; however in our case the rent was big and placed on the undersurface making it very difficult for the vascular surgeon to approach or repair it primarily

Esthetics with prosthetics in case of maxillary canine transposition: A clinical report

Transposition is a dental anomaly manifested by a positional interchange of two permanent teeth. The maxillary permanent canine usually transposes with the first premolar and occasionally with the lateral incisor. These are mainly genetically governed and are treated orthodontically if complete segment of tooth is present; in case of missing teeth, participation of cosmetic dentist is must. The present case report describes a situation where left canine to lateral incisor complete transposition was present along with a missing left central incisor. Esthetic rehabilitation of the “smile zone” was the major concern. Scrupulous treatment planning to esthetically contour transposed teeth according to their normal positions, i.e., transposed left canine to lateral incisor and transposed left lateral incisor to canine with replacement of missing tooth, was a challenge. Keywords: Canine transposition, composite veneers, smile designNigerian Journal of Clinical Practice •Jan-Mar 2012 • Vol 15 • Issue

Predictive process parameter selection for Selective Laser Melting Manufacturing: applications to high thermal conductivity alloys

There is growing interest in Laser Powder Bed Fusion (L-PBF) or Selective Laser Melting (SLM) manufacturing of high conductivity metals such as copper and refractory metals. SLM manufacturing of high thermal conductivity metals is particularly difficult. In case of refractory metals, the difficulty is amplified because of their high melting point and brittle behaviour. Rapid process development strategies are essential to identify suitable process parameters for achieving minimum porosities in these alloys, yet current strategies suffer from several limitations. We propose a simple approach for rapid process development using normalized process maps. Using plots of normalized energy density vs. normalized hatch spacing, we identify a wide processability window. This is further refined using analytical heat transfer models to predict melt pool size. Final optimization of the parameters is achieved by experiments based on statistical Design of Experiments concepts. In this article we demonstrate the use of our proposed approach for development of process parameters (hatch spacing, layer thickness, exposure time and point distance) for SLM manufacturing of molybdenum and aluminium. Relative densities of 97.4% and 99.7% are achieved using 200 W pulsed laser and 400 W continuous laser respectively, for molybdenum and aluminium, demonstrating the effectiveness of our approach for SLM processing of high conductivity materials

Recognizing Facial Expression using PCA and Genetic Algorithm

This paper presents an efficient method of recognition of facial expressions in a video. The works proposes highly efficient facial expression recognition system using PCA optimized by Genetic Algorithm .Reduced computational time and comparable efficiency in terms of its ability to recognize correctly are the benchmarks of this work. Video sequences contain more information than still images hence are in the research subject now-a-days and have much more activities during the expression actions. We use PCA, a statistical method to reduce the dimensionality and are used to extract features with the help of covariance analysis to generate Eigen –components of the images. The Eigen-components as a feature input is optimized by Genetic algorithm to reduce the computation cost

Laser Powder-Bed Fusion as an Alloy Development Tool: Parameter Selection for In-Situ Alloying Using Elemental Powders

The design of advanced alloys specifically tailored to additive manufacturing processes is a research field that is attracting ever-increasing attention. Laser powder-bed fusion (LPBF) commonly uses pre-alloyed, fine powders (diameter usually 15–45 µm) to produce fully dense metallic parts. The availability of such fine, pre-alloyed powders reduces the iteration speed of alloy development for LPBF and renders it quite costly. Here, we overcome these drawbacks by performing in-situ alloying in LPBF starting with pure elemental powder mixtures avoiding the use of costly pre-alloyed powders. Pure iron, chromium, and nickel powder mixtures were used to perform in-situ alloying to manufacture 304 L stainless steel cube-shaped samples. Process parameters including scanning speed, laser power, beam diameter, and layer thickness were varied aiming at obtaining a chemically homogeneous alloy. The scientific questions focused on in this work are: which process parameters are required for producing such samples (in part already known in the state of the art), and why are these parameters conducive to homogeneity? Analytical modelling of the melt pool geometry and temperature field suggests that the residence time in the liquid state is the most important parameter controlling the chemical homogeneity of the parts. Results show that in-situ alloying can be successfully employed to enable faster and cost-efficient rapid alloy development

Evaluation of Tribological Properties of Transesterified Cottonseed Oil by Adding Silicon Dioxide (SiO2) as an Additive

The usage of vegetable oils has increased in many applications as they possess desirable lubrication properties. However, the use is limited due to poor tribological properties. Many researchers have attempted to explore the performance of various vegetable oils and the effect of adding anti-wear additives on tribological properties. In the present work, bio lubricant is obtained from pure cottonseed oil (CSO). Silicon Dioxide, a useful catalyst, is used as an anti-wear additive. Oleic Acid surface-modified Silicon Dioxide (OA-SiO2) is added at 0.25%, 0.5%, 0.75%, and 1% weight concentrations in transesterified cottonseed oil (TCSO). After the addition of OA-SiO2 nanoparticles, the improvement in the lubrication properties has been seen. A four-ball tester is used to measure the coefficient of friction (COF) and wear scar diameter (WSD) of CSO, TCSO, and additive-added TCSO as per ASTM standard D 4172. Friction and wear tests reveal that the TCSO with OA-SiO2 nanoparticles shows better tribological properties. It is observed that WSD and COF of TCSO are reduced by 11.85 % and 24.88 % respectively by adding 0.75 weight % of OA-SiO2 nanoparticles. Present work shows that TCSO, on adding OA-SiO2 additives, can be a strong alternative for mineral oil

Evaluation of Tribological Properties of Transesterified Cottonseed Oil by adding Silicon Dioxide (SiO2) as an additive

The usage of vegetable oils has increased in many applications as they possess desirable lubrication properties. However, the use is limited due to poor tribological properties. Many researchers have attempted to explore the performance of various vegetable oils and the effect of adding anti-wear additives on tribological properties. In the present work, bio lubricant is obtained from pure cottonseed oil (CSO). Silicon Dioxide, a useful catalyst, is used as an anti-wear additive. Oleic Acid surface-modified Silicon Dioxide (OA-SiO2) is added at 0.25%, 0.5%, 0.75%, and 1% weight concentrations in transesterified cottonseed oil (TCSO). After the addition of OA-SiO2 nanoparticles, the improvement in the lubrication properties has been seen. A four-ball tester is used to measure the coefficient of friction (COF) and wear scar diameter (WSD) of CSO, TCSO, and additive-added TCSO as per ASTM standard D 4172. Friction and wear tests reveal that the TCSO with OA-SiO2 nanoparticles shows better tribological properties. It is observed that WSD and COF of TCSO are reduced by 11.85 % and 24.88 % respectively by adding 0.75 weight % of OA-SiO2 nanoparticles. Present work shows that TCSO, on adding OA-SiO2 additives, can be a strong alternative for mineral oil