Reference Values and Reference Correlations for the Thermal Conductivity and Viscosity of Fluids.

In this paper, reference values and reference correlations for the thermal conductivity and viscosity of pure fluids are reviewed. Reference values and correlations for the thermal conductivity and the viscosity of pure fluids provide thoroughly evaluated data or functional forms and serve to help calibrate instruments, validate or extend models, and underpin some commercial transactions or designs, among other purposes. The criteria employed for the selection of thermal conductivity and viscosity reference values are also discussed; such values, which have the lowest uncertainties currently achievable, are typically adopted and promulgated by international bodies. Similar criteria are employed in the selection of reference correlations, which cover a wide range of conditions, and are often characterized by low uncertainties in their ranges of definition.

Accurate lineshape spectroscopy and the Boltzmann constant.

Spectroscopy has an illustrious history delivering serendipitous discoveries and providing a stringent testbed for new physical predictions, including applications from trace materials detection, to understanding the atmospheres of stars and planets, and even constraining cosmological models. Reaching fundamental-noise limits permits optimal extraction of spectroscopic information from an absorption measurement. Here, we demonstrate a quantum-limited spectrometer that delivers high-precision measurements of the absorption lineshape. These measurements yield a very accurate measurement of the excited-state (6P1/2) hyperfine splitting in Cs, and reveals a breakdown in the well-known Voigt spectral profile. We develop a theoretical model that accounts for this breakdown, explaining the observations to within the shot-noise limit. Our model enables us to infer the thermal velocity dispersion of the Cs vapour with an uncertainty of 35 p.p.m. within an hour. This allows us to determine a value for Boltzmann's constant with a precision of 6 p.p.m., and an uncertainty of 71 p.p.m.

Polarizability of helium and gas metrology.

Using a quasispherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A(epsilon) in the limit of zero density. We obtained (A(epsilon,meas) - A(epsilon,theory))/A(epsilon) = (-1.8 +/- 9.1) x 10(-6), where the standard uncertainty (9.1 ppm) is a factor of 3.3 smaller than that of the best previous measurement. If the theoretical value of A(epsilon) is accepted, these data determine a value for the Boltzmann constant that is only 1.8 +/- 9.1 ppm larger than the accepted value. Our techniques will enable a helium-based pressure standard and measurements of thermodynamic temperatures.

Unusual presentations of sellar arachnoid cyst.

This report describes two unusual cases of parasellar arachnoid cyst with different neuro-ophthalmologic manifestations and clinical courses: a 33-year-old woman with parasellar arachnoid cyst, manifested by incongruous homonymous hemianopia, and a 64-year-old man with a presumed parasellar arachnoid cyst and bitemporal hemianopia that subsequently decompressed spontaneously. Parasellar arachnoid cyst is uncommon, and the clinical course has been incompletely described in the literature. Optimal treatment of patients with these cysts necessitates better understanding of their signs, symptoms, and clinical course.

Loss of vision alone may result in seesaw nystagmus.

A patient is described who developed seesaw nystagmus (SSN) associated with progressive severe vision loss due to cone-rod dystrophy. She was otherwise neurologically normal, and findings on magnetic resonance imaging of the brain were normal, including optic chiasm, meso-diencephalic junction, and brainstem. The literature is reviewed on neurologically normal patients with SSN and ocular vision loss, and the hypothesis is presented that SSN may become manifest as a result of vision loss alone, even in patients with chiasmal lesions, without disruption of central ocular motility pathways.

Familial hemiplegic migraine, nystagmus, and cerebellar atrophy.

Familial hemiplegic migraine (FHM) is an autosomal dominant disorder characterized by transient hemiplegia during the aura phase of a migraine attack. Nystagmus has been reported in individuals affected with this disorder, but the origin of the ocular motility findings is unknown. A three-generation family with FHM is described and clinical histories are outlined. Ocular motility evaluations were performed on 7 family members, 5 with a history of hemiplegic migraine and 2 without history of migraine. All affected family members had abnormal eye movements consistent with vestibulocerebellar dysfunction. Magnetic resonance imaging scans in affected family members revealed cerebellar vermian atrophy. DNA linkage analysis revealed a common marker in all the affected family members on chromosome 19. We suggest that the hemiplegic migraine attacks and the cerebellar degeneration are linked genetically and that the eye movements are not the ischemic sequelae of recurrent migraine. Strikingly similar ocular motility findings and cerebellar degeneration are reported in both FHM and a genetically related disorder, hereditary paroxysmal cerebellar ataxia (HPCA). The significance of these similarities is discussed along with a proposed pathophysiology for FHM.

Microflora associated with percutaneous craniofacial implants used for the retention of facial prostheses: a pilot study.

Craniofacial implants have been used successfully for the retention of facial prostheses. However, complications occur that can lead to the loss of implant integration. One such complication is infection possibly resulting from crevicular microflora activity. As part of an ongoing study, samples from crevicular sites surrounding 17 craniofacial implants were collected and submitted for microbiological assay. The results demonstrated the presence of opportunistic pathogens in many sites regardless of subjects' hygiene efforts. The significance of the findings is reviewed.

Contrast agent overdose causing brain retention of contrast, seizures and parkinsonism.

A patient received an overdose of intravascular contrast medium and experienced protracted seizures associated with radiographic evidence of prolonged retention of the contrast agent in the cerebral cortex, basal ganglia, and thalami. This is only the second report and the first survivor of a similar neurologic syndrome occurring in a patient after contrast agent overdose. After the seizures resolved, there was a transient period of parkinsonism probably due to the toxic effect of contrast on the basal ganglia.

Aggravation of myasthenia gravis by erythromycin.

Erythromycin is not currently recognized as causing clinical aggravation of myasthenia gravis. We report the case of a patient who experienced exacerbations of myasthenia gravis subsequent to each of several doses of intravenous erythromycin. We suggest that erythromycin can cause clinical worsening in patients with disease of the neuromuscular junction.

Stroke in neuroborreliosis.

A 20-year-old man suffered two thalamic infarctions during the course of neuroborreliosis and was successfully treated with intravenous ceftriaxone. Review of 11 additional cases of stroke and cerebral vasculitis in neuroborreliosis suggests that there is a meningovascular form of the infection with predilection for the posterior circulation and an association with the European strains of Borrelia burgdorferi.