Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator?

We study a model Dyson-Schwinger equation for the quark propagator closed using an {\it Ansatz} for the gluon propagator of the form \mbox{$D(q) \sim q^2/[(q^2)^2 + b^4]$} and two {\it Ans\"{a}tze} for the quark-gluon vertex: the minimal Ball-Chiu and the modified form suggested by Curtis and Pennington. Using the quark condensate as an order parameter, we find that there is a critical value of $b=b_c$ such that the model does not support dynamical chiral symmetry breaking for $b>b_c$. We discuss and apply a confinement test which suggests that, for all values of $b$, the quark propagator in the model {\bf is not} confining. Together these results suggest that this Ansatz for the gluon propagator is inadequate as a model since it does not yield the expected behaviour of QCD.Comment: 21 Pages including 4 PostScript figures uuencoded at the end of the file. Replacement: slight changes of wording and emphasis. ADP-93-215/T133, ANL-PHY-7599-TH-93, FSU-SCRI-93-108, REVTEX 3.

Status of Muon Collider Research and Development and Future Plans

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam

Electric dipole moments and the search for new physics

Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well beyond those reached directly at high energy colliders. Discrimination between different physics models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss the current status and prospects in the near future for a compelling suite of such experiments, along with developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and endorsement

The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Is Fusion Indicated for Lumbar Spinal Disorders?

Study Design A review of relevant literature and clinical experience with lumbar spinal disorder. Objectives To discuss the indications for fusions and lumbar spinal disorders. Summary of Background Data Fusion of the lumbar spine is performed frequently, but indications have not been defined clearly. The literature and the Authors\u27 experience with these indications are reviewed. Methods A comprehensive review of the literature and the authors\u27 clinical experience with lumbar spinal Instability was critically examined, Specifically, the role of fusion, with or without instrumentation versus decompression alone was assessed. From this, a set of definitive and relative indications for spinal arthrodesis in a variety of disorders of the tumbar spine could be established. Results Once the diagnosis of lumbar spinal instability is established, fusion is indicated. However, fusion without spinal instrumentation has a high pseudar-throsis rate and ?oorer patient outcome, This spinal instrumentation should be used as an adjunct when considering spinal arthrodesis. Conclusions Definitive indications for spinal fusions are trauma, tumor and infection, iatrogenic instability, or ischemic spondylolisthesis. Relative indications for fusions are degenerative spondylolisthesis, abnormal movement visualized on dynamic films with appropriate pain or neurologic defieit, and mechanical pain. Lumbar fusion is rarely indicated for routine discectomy, abnormal results of radiography without appropriate clinical findings, or stable spinal stenosis. © 1995, Lippincott-Ravcn Publishers

Ruptured Giant Aneurysm of an Occluded Middle Cerebral Artery in a Severe-Grade Patient: Case Report

A 27-YEAR-OLD WOMAN presented with a ruptured giant aneurysm of the right middle cerebral artery, occlusion of the artery distal to the aneurysm, and an intraparenchymal hematoma. Before emergent surgery, her condition deteriorated to a Glasgow Coma Scale score of 4 and a Hunt and Hess grade of V. Electroencephalographic response on the right, initially absent, was present toward the end of the surgery. Postoperative angiography demonstrated good filling of the previously occluded distal middle cerebral artery. The simultaneous occurrence of hemorrhage from a giant intracranial aneurysm and occlusion of the parent artery is extremely rare, and this is the first case we found in the literature in which the patient survived. The treatment strategy and outcome are discussed. Copyright © by the Congress of Neurological Surgeons

Minimally Invasive Transforaminal Lumbar Interbody Fusions and Fluoroscopy: A Low-Dose Protocol to Minimize Ionizing Radiation

Object. There is an increasing awareness of radiation exposure to surgeons and the lifelong implications of such exposure. One of the main criticisms of minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) is the amount of ionizing radiation required to perform the procedure. The goal in this study was to develop a protocol that would minimize the fluoroscopy time and radiation exposure needed to perform an MIS TLIF without compromising visualization of the anatomy or efficiency of the procedure. Methods. A retrospective review of a prospectively collected database was performed to review the development of a low-dose protocol for MIS TLIFs in which a combination of low-dose pulsed fluoroscopy and digital spot images was used. Total fluoroscopy time and radiation dose were reviewed for 50 patients who underwent single-level MIS TLIFs. Results. Fifty patients underwent single-level MIS TLIFs, resulting in the placement of 200 pedicle screws and 57 interbody spacers. There were 28 women and 22 men with an average age of 58.3 years (range 32-78 years). The mean body mass index was 26.2 kg/m 2 (range 17.1-37.6 kg/m 2 ). Indications for surgery included spondylolisthesis (32 patients), degenerative disc disease with radiculopathy (12 patients), and recurrent disc herniation (6 patients). Operative levels included 7 at L3-4, 40 at L4-5, and 3 at L5-S1. The mean operative time was 177 minutes (range 139-241 minutes). The mean fluoroscopic time was 18.72 seconds (range 7-29 seconds). The mean radiation dose was 0.247 mGym 2 (range 0.06046-0.84054 mGym 2 ). No revision surgery was required for any of the patients in this series. Conclusions. Altering the fluoroscopic technique to low-dose pulse images or digital spot images can dramatically decrease fluoroscopy times and radiation doses in patients undergoing MIS TLIFs, without compromising image quality, accuracy of pedicle screw placement, or efficiency of the procedure. © AANS, 2013

Anatomic Basis for Minimally Invasive Resection of Intradural Extramedullary Lesions in Thoracic Spine

Objective Since the first resections of intradural extramedullary neoplasms, neurosurgeons have tended to preserve as much of the integrity of the spine as possible while ensuring a safe corridor to resect these lesions. A dimensional analysis of intradural lesions superimposed on a dimensional analysis of the thoracic canal would provide the anatomic basis for a minimal access approach. The authors report the results of such an analysis on a series of patients with intradural extramedullary lesions. Methods A retrospective analysis was undertaken of 26 thoracic intradural extramedullary lesions managed with open or minimally invasive resection. The size of each lesion was measured in the rostrocaudal, lateral, and anteroposterior dimensions and then averaged and compared with reported dimensions of the thoracic spinal canal. Results The mean (range) dimensions of the surgically resected thoracic lesions were 18.6 mm (10–25 mm) for rostrocaudal, 13.0 mm (7–18 mm) for lateral, and 13.6 mm (9–17 mm) for anteroposterior. No patient had any evidence of thoracic canal remodeling. Conclusions Thoracic intradural extramedullary lesions become symptomatic as they approach the limits of the thoracic canal, resulting in an inherent dimensional limitation in the rostrocaudal, lateral, and anteroposterior dimensions. Displacement of the spinal cord by the lesion to one side further favors a minimally invasive unilateral approach. A paraspinal unilateral hemilaminectomy approach with a 35 × 20 mm exposure centered over the lesion offers a safe surgical corridor for resection while preserving the posterior tension band, facet complexes, and paraspinal musculature

Extreme Lateral Supracerebellar Infratentorial Approach to the Posterolateral Mesencephalon: Technique and Clinical Experience

OBJECTIVE: Lesions situated posterolaterally along the mesencephalon present neurosurgeons with a special challenge. The midline and paramedian variations of the supracerebellar infratentorial approaches do not adequately expose this region. The subtemporal approach risks injury to the vein of Labbe. An extreme lateral supracerebellar infratentorial approach with more radical resection of bone superiorly and laterally, and skeletonization of the sigmoid and transverse sinuses, was used to approach lesions at this location in eight patients. The clinical series is presented, and the regional surgical anatomy is described. METHODS: Five cavernous malformations, two juvenile pilocytic astrocytomas, and one peripheral superior cerebellar artery aneurysm located in this region were approached in eight patients. In this extreme lateral approach, the sigmoid sinus is unroofed more superiorly and the bone flap includes not only a posterior fossa craniotomy but also a portion that extends just above the transverse sinus. The dural opening is based along the transverse and sigmoid sinuses. After the cerebrospinal fluid has been drained, the lateral aspect of the brainstem is approached via the cerebellar surface. A proximal tentorial incision offers additional rostral exposure where needed. RESULTS: Seven patients in this series underwent successful resection of their lesion. The remaining patient\u27s aneurysm was clipped successfully with no major complications. CONCLUSION: The extreme lateral supracerebellar infratentorial approach differs from the midline and paramedian supracerebellar infratentorial variants in the area of exposure, patient positioning, and location of the craniotomy. The technique is effective for approaching the posterolateral mesencephalon

Provisional Ipsilateral Expandable Rod for Disc Space Distraction in Minimally Invasive Transforaminal Lumbar Interbody Fusion: Operative Technique

BACKGROUND: Lumbar disc degeneration may be so advanced and asymmetrical that transforaminal access to the interbody space is limited. The extent of collapse may compromise the capacity to restore disc height and coronal balance in minimally invasive approaches. Although a variety of distractors are available for open approaches, currently there is no feasible distractor that is functional within a minimally invasive retractor. OBJECTIVE: To describe the development of a provisional ipsilateral expandable rod for use in minimally invasive surgery for transforaminal lumbar interbody fusions to optimize access to the disc space, thereby facilitating placement of an interbody spacer. METHODS: The authors report the clinical and radiographic data for 30 patients (3 open and 27 minimally invasive surgeries) with advanced degenerative disc disease in whom a provisional ipsilateral expandable rod was used to restore coronal balance and maintain disc height for interbody preparation and placement. Preoperative disc heights were measured, and the height of interbody spacer recorded. Mean restoration of disc heights was calculated. RESULTS: The provisional ipsilateral expandable rod was successfully applied in both open exposures and within a minimally invasive retractor. The mean preoperative disc height was 4.9 mm (range, 1-9 mm), the mean height of the spacer inserted was 11.1 mm (range, 8-15 mm), and the mean increase in disc height was 6.2 mm (range, 5-11 mm). CONCLUSION: A provisional ipsilateral expandable rod is feasible in either minimally invasive or open approaches. It has the capacity to maintain the disc height achieved by paddle distractors. This facilitates both the disc preparation and optimizes restoration of disc height and interbody spacer placement