Sr lattice clock at 1 x 10(-16) fractional uncertainty by remote optical evaluation with a Ca clock.

Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and application of these optical standards. Through this remote comparison and a proper design of lattice-confined neutral atoms for clock operation, we evaluate the uncertainty of a strontium (Sr) optical lattice clock at the 1 x 10(-16) fractional level, surpassing the current best evaluations of cesium (Cs) primary standards. We also report on the observation of density-dependent effects in the spin-polarized fermionic sample and discuss the current limiting effect of blackbody radiation-induced frequency shifts.

Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1x10(-15).

We demonstrate phase and frequency stabilization of a diode laser at the thermal noise limit of a passive optical cavity. The system is compact and exploits a cavity design that reduces vibration sensitivity. The subhertz laser is characterized by comparison with a second independent system with similar fractional frequency stability (1x10(-15) at 1 s). The laser is further characterized by resolving a 2 Hz wide, ultranarrow optical clock transition in ultracold strontium.

Experimental implementation of optical clockwork without carrier-envelope phase control.

We demonstrate optical clockwork without the need for carrier-envelope phase control by use of sum-frequency generation between a continuous-wave optical parametric oscillator at 3.39 microm and a femtosecond mode-locked Ti:sapphire laser with two strong spectral peaks at 834 and 670 nm, a spectral difference matched by the 3.39-microm radiation.

Malingering vs. the factitious personality in chiropractic practice.

This article details how to identify and treat the malingering patient, which we feel is seen more often than was originally thought in chiropractic practice. A historical perspective of a malingering vs. a factitious personality is examined. The factitious patient is reviewed in detail with special attention to the classic case of Munchausen syndrome. An extensive treatment plan is discussed, including short- and long-term care. The common characteristics, objective tests and studies are reviewed. We theorize that due to our increasing involvement in Workers' Compensation and personal injury cases our attention should be focused more closely on the possibility of these types of patients entering our office.

Diagnosis of perineurial arachnoid cysts using computed tomography: technical and clinical considerations.

Perineurial arachnoid cysts are often multiple lesions that are usually found in the lumbosacral area. These cysts may cause compression of surrounding structures. Examination of the first, second and third sacral nerves should be performed on patients with prolonged symptoms of a herniated disc or cauda equina syndrome. Three cases are presented for which computed tomography provided accurate, noninvasive diagnosis. Perineurial cysts are often associated with asymptomatic herniated disc; thus, surgery on the disc with an underlying symptomatic cyst may result in a failed back syndrome.

Ossification of the posterior longitudinal ligaments: a cause of spinal stenosis syndrome.

Spinal Stenosis Syndrome (SSS) causes varying radiculopathies and myelopathies by compressing the spinal cord, rootlets and nerves within the bony canal. An enlarged and ossified posterior longitudinal ligament, a rare cause of the syndrome, can occupy up to 80% of the cervical spinal canal resulting in severe, sometimes permanent myelopathy. The clinical and the radiographic findings are discussed.

Nerve root ischemia and pain secondary to spinal stenosis syndrome: technical and clinical considerations.

Spinal stenosis is a loosely used term meaning different things to different people. A clinical picture of episodic sciatic pain and a normal physical examination usually confronts the physician. Various anatomic lesions can produce traction and compression of spinal nerve roots. The pathophysiology of the compression and the resultant ischemia of spinal nerve roots is discussed. Accurate diagnosis may allow conservative care, including manipulation, to be utilized prior to surgical consideration.

A review of radiographic differential diagnosis of common degenerative spinal disorders.

Radiographic criteria for the diagnosis of degenerative spinal conditions is discussed and reviewed. Pathophysiological aspects are correlated with plain film radiography and Multiplanar Reconstructive Computerized Tomography to provide the practitioner with information relative to better diagnostic capabilities when dealing with common spinal disorders.

Malignant degeneration of hereditary multiple exostosis: a case history.

Hereditary multiple exostosis is not an uncommon condition; and must be watched for malignant degeneration. A case is reported which has both typical and atypical characteristics. A young male presented with painless metaphyseal lumps, but in addition had a suspicious ischial mass which, when further evaluated, was found to be malignant.