Genetic Programming in Designing Advanced Metamaterial Absorbers

M.S

Validation of Different Combination of Three Reversing Half-Hitches Alternating Posts (RHAPs) Effects on Arthroscopic Knot Integrity

Introduction. With arthroscopic techniques being used, the importanceof knot tying has been examined. Previous literaturehas examined the use of reversing half-hitches on alternatingposts (RHAPs) on knot security. Separately, there has been researchregarding different suture materials commonly used inthe operating room. The specific aim of this study was to validatethe effect of different stacked half-hitch configuration anddifferent braided suture materials on arthroscopic knot integrity. Methods. Three different suture materials tied withfive different RHAPs in arthroscopic knots were compared.A single load-to-failure test was performed andthe mean ultimate clinical failure load was obtained. Results. Significant knot holding strength improvement wasfound when one half-hitch was reversed as compared to baselineknot. When two of the half-hitches were reversed, therewas a greater improvement with all knots having a mean ultimateclinical failure load greater than 150 newtons (N). Comparisonof the suture materials demonstrated a higher meanultimate clinical failure load when Force Fiber® was used andat least one half-hitch was reversed. Knots tied with eitherForce Fiber® or Orthocord® showed 0% chance of knot slippagewhile knots tied with FiberWire® or braided fishing linehad about 10 and 30% knot slippage chances, respectively. Conclusion. A significant effect was observed in regards to bothstacked half-hitch configuration and suture materials used onknot loop and knot security. Caution should be used with tyingthree RHAPs in arthroscopic surgery, particularly witha standard knot pusher and arthroscopic cannulas. The findingsof this study indicated the importance of three RHAPsin performing arthroscopic knot tying and provided evidenceregarding discrepancies of maximum clinical failure loads observedbetween orthopaedic surgeons, thereby leading to bettersurgical outcomes in the future. KS J Med 2017;10(2):35-39

A possible method for non-Hermitian and non-PTPT-symmetric Hamiltonian systems

A possible method to investigate non-Hermitian Hamiltonians is suggested through finding a Hermitian operator $\eta_+$ and defining the annihilation and creation operators to be $\eta_+$-pseudo-Hermitian adjoint to each other. The operator $\eta_+$ represents the $\eta_+$-pseudo-Hermiticity of Hamiltonians. As an example, a non-Hermitian and non-$PT$-symmetric Hamiltonian with imaginary linear coordinate and linear momentum terms is constructed and analyzed in detail. The operator $\eta_+$ is found, based on which, a real spectrum and a positive-definite inner product, together with the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution, are obtained for the non-Hermitian and non-$PT$-symmetric Hamiltonian. Moreover, this Hamiltonian turns out to be coupled when it is extended to the canonical noncommutative space with noncommutative spatial coordinate operators and noncommutative momentum operators as well. Our method is applicable to the coupled Hamiltonian. Then the first and second order noncommutative corrections of energy levels are calculated, and in particular the reality of energy spectra, the positive-definiteness of inner products, and the related properties (the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution) are found not to be altered by the noncommutativity.Comment: 15 pages, no figures; v2: clarifications added; v3: 16 pages, 1 figure, clarifications made clearer; v4: 19 pages, the main context is completely rewritten; v5: 25 pages, title slightly changed, clarifications added, the final version to appear in PLOS ON

Geometric aspects of space-time reflection symmetry in quantum mechanics

For nearly two decades, much research has been carried out on properties of physical systems described by Hamiltonians that are not Hermitian in the conventional sense, but are symmetric under space-time reflection; that is, they exhibit PT symmetry. Such Hamiltonians can be used to model the behavior of closed quantum systems, but they can also be replicated in open systems for which gain and loss are carefully balanced, and this has been implemented in laboratory experiments for a wide range of systems. Motivated by these ongoing research activities, we investigate here a particular theoretical aspect of the subject by unraveling the geometric structures of Hilbert spaces endowed with the parity and time-reversal operations, and analyze the characteristics ofPT -symmetric Hamiltonians. A canonical relation between aPT -symmetric operator and a Hermitian operator is established in a geometric setting. The quadratic form corresponding to the parity operator, in particular, gives rise to a natural partition of the Hilbert space into two halves corresponding to states having positive and negative PT norm. Positive definiteness of the norm can be restored by introducing a conjugation operator C ; this leads to a positive-definite inner product in terms of CPT conjugation

Functional Outcomes of Thoracolumbar Junction Spine Fractures

Introduction. Few studies have evaluated the functionaloutcomes of traumatic thoracic and lumbar vertebral bodyfractures. This study evaluated the functional and clinicaloutcomes of patients, who sustained a fracture to thethoracolumbar area of the spine (T10 to L2 region), with≥ 25° kyphosis versus those with less kyphotic curvature. Methods. The trauma registry records of two level 1 traumacenters using ICD-9 codes for fracture to the thoracolumbarjuncture (T10 to L2 region) were reviewed. Kyphosis anglewas measured on the standing lateral thoracolumbar (T1 -L5) radiograph at initial trauma and at clinical follow-up.Functional outcome questionnaires, including the OswestryDisability Questionnaire (ODQ), the Roland Morris DisabilityQuestionnaire (RMDQ), and the Nottingham Health Profile(NHP), were evaluated at clinical follow-up. Work statusand medication used after trauma also were recorded. Results. A total of 38 patients met the inclusive criteria. Seventeenpatients (45%) had ≥ 25° kyphosis and 21 patients (55%)had < 25° kyphosis at follow-up. These two groups were similarbased on sex and age. Based on the ODQ Score, the RMDQScore, and the NHP, no statistically significant differenceswere detected between the two groups in regards to energy,pain, mobility, emotional reaction, social isolation, and sleep. Conclusions. Patients who sustained a fracture to the thoracolumbararea of the spine with ≥ 25° kyphosis do notreport worse clinical outcomes. When using the kyphosisangle as an indication for surgery, it should be used withcaution and not exclusively. KS J Med 2017;10(2):30-34

Total absorption of visible light in ultrathin weakly absorbing semiconductor gratings

© 2016 Optical Society of America. The perfect absorption of light in subwavelength thickness layers generally relies on exotic materials, metamaterials or thick metallic gratings. Here we demonstrate that total light absorption can be achieved in ultra-thin gratings composed of conventional materials, including relatively weakly-absorbing semiconductors, which are compatible with optoelectronic applications such as photodetectors and optical modulators. We fabricate a 41 nm thick antimony sulphide grating structure that has a measured absorptance of A = 99.3% at a visible wavelength of 591 nm, in excellent agreement with theory. We infer that the absorption within the grating is A = 98.7%, with only A = 0.6% within the silver mirror. A planar reference sample absorbs A = 7.7% at this wavelength