Lie Semigroup Operator Algebras.

The parabolic algebra Ap and the hyperbolic algebra Ah are nonselfadjoint w*-closed operator algebras which were first considered by A. Katavolos and S. C. Power. In [KP97] and [KP02] they showed that their invariant subspace lattices are homeomorphic to compact connected Euclidean manifolds, and that the parabolic algebra is reflexive in the sense of Halmos. We give a new proof of the reflexivity of the parabolic algebra through analysis of Hilbert-Schmidt operators. We also show that there are operators in Ap with nontrivial kernel. We then consider some natural "companion algebras" of the parabolic algebra which leads to a compact subspace lattice known as the Fourier-Plancherel sphere. We show that the unitary automorphism group of this lattice is isomorphic to a semidirect product of R2 and SL2(R). A proof that the hyperbolic algebra is reflexive follows by an essentially identical analysis of Hilbert-Schmidt operators to that which was used to establish the reflexivity of Ap. We also present a transparent proof of a known result concerning a strong operator topology limit of projections. Both of the Katavolos-Power algebras are generated as w*-closed operator algebras by the image of a semigroup of a Lie group under a unitary-valued representation. Following [KP02], we call such operator algebras Lie semigroup operator algebras. We seek new examples of such algebras by considering the images of the semigroup SL2(R+) of the Lie group SL2(R) under unitary-valued representations of SL2 (R). We show that a particular Lie semigroup operator algebra A+ arising in this way is reflexive and that it is the operator algebra leaving a double triangle subspace lattice invariant. Surprisingly, A+ is generated as a w*-closed algebra by the image of a proper subsemigroup of SL2(R+)

Does the Cage Position in Transforaminal Lumbar Interbody Fusion Determine Unilateral versus Bilateral Screw Placement?: A Review of the Literature

This literature review examines the relative placement of the interbody cage with respect to the unilateral screw construct to address the need for bilateral screw placement versus unilateral screw placement. Transforaminal lumbar interbody fusion (TLIF) has become a widely used technique for correcting lumbar intervertebral pathologies. This review addresses the necessity for further study on the effects of the relative position of intervertebral cage placement on the outcome of lumbar spine surgery after TLIF with unilateral pedicle screw fixation. Previous studies have addressed various factors, including posterior screw fixation, cage size, cage shape, and number of levels fused, that impact the biomechanics of the lumbar spine following TLIF. A simple survey of the literature was conducted. A search of the English literature was conducted using the keywords ‘TLIF,’ ‘transforaminal lumbar interbody fusion,’ ‘graft placement,’ ‘graft position,’ ‘cage position,’ ‘cage placement,’ ‘unilateral pedicle screw,’ ‘unilateral TLIF cage placement,’ ‘lumbar biomechanics,’ ‘lumbar stability,’ ‘lumbar fusion,’ and ‘lumbar intervertebral cage’ with various combinations of the operators ‘AND’ and ‘OR’ and no date restrictions. Seventeen articles in the English literature that were most relevant to this research question were identified. To the best of our knowledge, there are no published data addressing the effects of cage placement relative to the unilateral screw on lumbar stability in TLIF with unilateral pedicle screw fixation. Investigation of the effects of cage placement is, thus, warranted to achieve optimal clinical outcomes in patients undergoing TLIF with unilateral pedicle screw fixation

A review of the current treatment methods for posthaemorrhagic hydrocephalus of infants

Posthaemorrhagic hydrocephalus (PHH) is a major problem for premature infants, generally requiring lifelong care. It results from small blood clots inducing scarring within CSF channels impeding CSF circulation. Transforming growth factor – beta is released into CSF and cytokines stimulate deposition of extracellular matrix proteins which potentially obstruct CSF pathways. Prolonged raised pressures and free radical damage incur poor neurodevelopmental outcomes. The most common treatment involves permanent ventricular shunting with all its risks and consequences

Taking MT evaluation metrics to extremes : beyond correlation with human judgments

Automatic Machine Translation (MT) evaluation is an active field of research, with a handful of new metrics devised every year. Evaluation metrics are generally benchmarked against manual assessment of translation quality, with performance measured in terms of overall correlation with human scores. Much work has been dedicated to the improvement of evaluation metrics to achieve a higher correlation with human judgments. However, little insight has been provided regarding the weaknesses and strengths of existing approaches and their behavior in different settings. In this work we conduct a broad meta-evaluation study of the performance of a wide range of evaluation metrics focusing on three major aspects. First, we analyze the performance of the metrics when faced with different levels of translation quality, proposing a local dependency measure as an alternative to the standard, global correlation coefficient. We show that metric performance varies significantly across different levels of MT quality: Metrics perform poorly when faced with low-quality translations and are not able to capture nuanced quality distinctions. Interestingly, we show that evaluating low-quality translations is also more challenging for humans. Second, we show that metrics are more reliable when evaluating neural MT than the traditional statistical MT systems. Finally, we show that the difference in the evaluation accuracy for different metrics is maintained even if the gold standard scores are based on different criteria

Lack of Current Recommendations for Resuming Sexual Activity Following Spinal Surgery

Patients are faced with many questions surrounding the after effects of the various surgical procedures and their ability to return to preoperative activities. While patients often question whether surgery would provide alleviation of pain, weakness, and instability, they often have additional questions about sexual activity during their convalescence that are not always addressed. Although the literature shows postsurgical improvement in sexual activity in association with improved low back pain, reports vaguely address the variability in sexual activity recommendations based on anatomic location and type of spinal surgery. We conducted a PubMed search of the English language from 1990 to 2018 with the following keywords: sexual activity, postoperative, spinal fusion, spinal decompression, functional outcomes, laminectomy, rehabilitation, biomechanics, lumbar disc surgery, metabolic energy expenditure, coital position, and Oswestry Disability Index. Additional studies are needed that survey both patients and spine surgeons to examine current recommendations and to help formulate future guidelines

Inpatient Hospital Outcomes and its Association with Insurance Type Among Pediatric Neurosurgery Trauma Patients

To assess the association of insurance status and inpatient hospital outcomes among a nationally representative population of pediatric trauma neurosurgery patients. The 2006, 2009, and 2012 Healthcare Cost and Utilization Project Kids' Inpatient Database was queried for all pediatric neurosurgery patients (birth through 17 years) with primary International Classification of Diseases, Ninth Edition, Clinical Modification, procedure codes for trauma or hematoma. Self-pay patients were 2.5 times more likely to die during hospitalization. Results also showed that pediatric neurosurgery patients with private insurance had a reduced length of stay and were more likely to have a favorable disposition at discharge. Insurance status is significantly associated with mortality, length of stay, and favorable discharge disposition among pediatric neurosurgery trauma patients. Further studies are needed to examine the underlying mechanism of the observed associations

Interlaminar stabilization and decompression for the treatment of bilateral juxtafacet cysts: Case report and literature review

•Lumbar juxtafacet cysts are typically treated by resection alone or resection combined with posterior instrumentation.•Resection with instrumentation is associated with a lower rate of recurrence but also with increased cost and morbidity.•We present a case of bilateral juxtafacet cysts causing neurogenic claudication treated with decompression and interlaminar stabilization.•Complete symptom resolution was sustained at one-year follow-up.•Decompression followed by interlaminar stabilization may be a reasonable alternative for some patients. Lumbar juxtafacet cysts (JFCs) are a common cause of lumbar radiculopathy which tend to occur in areas of increased facet mobility. While resection alone is a possible treatment, recent publications suggest that laminectomy alone for JFCs may not yield as favorable an outcome as laminotomies reinforced with posterior dynamic hardware. The Coflex® is a novel interlaminar stabilization device that has been shown to achieve comparable results to rigid fusion in the management of lumbar stenosis in patients with no more than grade one anterolisthesis, and superior performance compared to laminectomy alone when a combined outcome score was used. We describe the combined use of dynamic posterior element fusion with primary cyst resection in the management of bilateral JFCs. A 71-year-old man who developed a progressive left L4 radiculopathy along with new urinary incontinence was found to have bilateral L3/4 JFCs causing significant lumbar stenosis and neurogenic claudication. After treatment with primary cyst resection and interlaminar stabilization, the patient experienced complete symptom resolution and was discharged to inpatient-rehabilitation on post-operative day 1. While current recommendations for the management of juxtafacet cysts causing progressive neurologic symptoms include surgical cyst removal and lumbar decompression with or without fusion, the role of dynamic interlaminar stabilization has not been explored. Direct decompression followed by interlaminar stabilization may represent an alternative for patients to simultaneously benefit from a decompression of their juxtafacet cysts while affording posterior element reconstruction