No abstract

Ollier disease (Spranger type I) is a rare bone disease that is characterized by multiple enchondromatosis with a typical asymmetrical distribution and confined to the appendicular skeleton. The pathogenesis of enchondromatosis is not clearly understood. Recently, heterozygous mutations of PTHR1, IDH1 (most common), and/or IDH2 genes have been suggested by various authors as genetic aberrations. Genomic copy number alterations and mutations controlling many vital pathways are responsible for the pathogenesis of Ollier disease. A comprehensive description of all genetic events in Ollier disease is presented in this article. Clinically, Ollier disease has a wide variety of presentations. This article describes the plethora of clinical features, both common and rare, associated with Ollier disease. Multiple enchondromas are most commonly seen in phalanges and metacarpals. Radiologically, Ollier disease presents with asymmetrical osteolytic lesions with well-defined, sclerotic margins. In this article, various radiological features of Ollier disease, including radiographs, computed tomography, and magnetic resonance imaging, are also discussed. Gross pathology, cytological, and histological features of both Ollier disease and its malignant transformation are outlined. Although treatment is conservative in most cases, different possible treatment options for difficult cases are discussed. In the literature, there is a paucity of data about the disease, including diagnosis, management, prognostication, and rehabilitation, necessitating a comprehensive review to further define all of the possible domains related to this disease.

Spinal cord injury without fractures or bony malalignment on either plain radiographs or computed tomography (SCIWORA) is most commonly found in the paediatric age group. In recent years, magnetic resonance imaging (MRI) has been used to evaluate these patients. The present communication describes SCIWORA in 15 adult patients investigated by MRI. Of the 151 patients with spinal cord injury in 1 year, 15 adult patients had cervical SCIWORA. All patients were evaluated by MRI. The age ranged from 20 ± 60 years. Eleven patients had partial cord injury, two had a complete cord syndrome while two had a central cord syndrome. MRI demonstrated an intervertebral disc prolapse in six patients, intramedullary haematoma/ contusion in four and cord oedema in four patients. One patient had multiple disc prolapses and associated intramedullary haematoma. Patients with disc prolapse were operated upon and all showed neurological improvement. The rest of the patients were managed conservatively. There was mild improvement in patients with intramedullary haematomas while those with cord oedema alone showed moderate recovery. The pathogenesis of adult SCIWORA is possibly di erent from that in paediatric age group. Most of the patients with SCIWORA show some abnormality on MR imaging. MRI should therefore be done in all patients with spinal cord injury for diagnostic and prognostic purposes.

We trap absorbing micro-particles in air by photophoretic forces generated using a single loosely focused Gaussian trapping beam. We measure a component of the radial Brownian motion of a trapped particle cluster and determine the power spectral density, mean squared displacement, and normalized position and velocity autocorrelation functions in order to characterize the photophoretic body force in a quantitative fashion for the first time. The trapped particles also undergo spontaneous rotation due to the action of this force. This is evident from the spectral density that displays clear peaks at the rotation and the particles' inertial resonance frequencies. We fit the spectral density to the well-known analytical function derived from the Langevin equation, measure the resonance and rotation frequencies and determine values for particle mass that we verify at different trapping laser powers with reasonable accuracy.

We combine optical tweezers with feedback to impose arbitrary potentials on a colloidal particle. The feedback trap detects a particle's position, calculates a force based on an imposed “virtual potential,” and shifts the trap center to generate the desired force. We create virtual harmonic and double-well potentials to manipulate particles. The harmonic potentials can be chosen to be either weaker or stiffer than the underlying optical trap. Using this flexibility, we create an isotropic trap in three dimensions. Finally, we show that we can create a virtual double-well potential with fixed well separation and adjustable barrier height. These are accomplished at length scales down to 11 nm, a feat that is difficult or impossible to create with standard optical-tweezer techniques such as time sharing, dual beams, or spatial light modulators.