Tuning the reduction potential of quinones by controlling the effects of hydrogen bonding, protonation and proton-coupled electron transfer reactions.

An all-organic cell comprising 2,3-dimethyl-1,4-napthoquinone and pyrano[3,2-f]chromene as electroactive elements exhibited a good combination of large cell voltage and stability of the reduced quinone upon the addition of diethyl malonate (a weak organic acid), as compared to the addition of trifluoroethanol (which led to a high cell potential but low stability via strong hydrogen bonding interactions) and the addition of trifluoroacetic acid (which led to a lower cell potential but high stability through proton transfer).

Tetrathiafulvalene aids in the atomic spectroscopic determination of total mercury.

The determination of mercury simultaneously with other elements via inductively coupled plasma-mass spectrometry (ICP-MS) in airborne particulate matter (PM2.5) is still challenging due to the lack of accuracy for the low level mercury concentrations as a result of its volatility and tendency to adhere to the walls of the sample introduction system. This study investigated the effect of existing (gold and methionine) and new (lithium tetrathiafulvalene carboxylate (LiCTTF)) preservation agents in order to improve the determination of trace mercury in PM2.5 samples. Statistical analysis revealed that a concentration of 10 µg mL-1 of LiCTTF was sufficient to obtain highly accurate results with t values of 0.1044-1.1239 which are considerably less than the critical t value of 1.8 and apparent recoveries of 85-100%. An evaluation of the method revealed a spiked mercury recovery of 91% and a detection limit of 0.05 ng mL-1. The method was tested for the determination of trace metals in PM2.5 from atmospheric samples and led to the detection of low elemental concentrations in Singapore's atmosphere. The mechanism for the interaction of mercury with LiCTTF and tetrathiafulvalene (TTF) was studied by conducting in situ electrochemical studies. Cyclic voltammetry and square-wave voltammetry analyses of mercury, and mercury in presence of LiCTTF and TTF revealed complexation between the metal and sulfur-containing compounds.

Sulfoxidation of alkenes and alkynes with NFSI as a radical initiator and selective oxidant.

Sulfoxides are important functional molecules. We develop a short-route (one-pot) synthesis of this class of molecules by reacting thiols with alkenes or alkynes under mild and metal-free conditions. N-Fluorobenzenesulfonimide (NFSI) is used to play dual roles: as a radical initiator for a thiol-ene/-yne reaction to form sulfide adducts, and as efficient oxidant for conversion of the sulfides formed in situ to sulfoxides. Over-oxidation of the sulfoxides to sulfones is avoided in our approach.

Primary-Colored Electrochromism of 1,4-Phenylenediamines.

Ten 1,4-phenylenediamines were studied using electrochemical techniques (voltammetry and controlled potential electrolysis) and UV/Vis spectroscopy under ambient conditions. All compounds demonstrated vibrant color changes upon one-electron electrochemical oxidation in acetonitrile, with most displaying a primary color (red, green, blue, or yellow) in their oxidized state. The four electrochromes that exhibited the most intense color changes were examined by using a gold micromesh electrode laminated inside a polymer film to determine their electrochromic properties in solution (contrast ratios, chromatic efficiency, and cycle life). Their colored radical cations were also characterized by electron paramagnetic resonance spectroscopy as well as monitored for color retention over a period of 24 hours. Notably, only relatively small potentials were required to initiate the chromatic changes and the oxidized forms of the compounds were long-lived and unaffected by atmospheric oxygen or moisture.

Patterns of muscle atrophy in the lower limbs in patients with Charcot-Marie-Tooth disease as measured by magnetic resonance imaging.

Intrinsic atrophy of the calf musculature is a common finding in Charcot-Marie-Tooth disease. Peroneal nerve atrophy leading to weakness in the anterior and lateral compartments is the most common clinical pattern, but considerable variability exists in the pattern of atrophy. Magnetic resonance imaging offers a valuable method for identifying the distribution and symmetry of muscle degeneration. Twenty-three patients with Charcot-Marie-Tooth disease had axial T-1 magnetic resonance images obtained at proximal, middle and distal calf muscle locations. Areas of fatty infiltration and muscle atrophy were measured in the four calf muscle compartments. The worst areas of involvement, on a scale of one to four, with four being worst, were in the lateral compartment in the mid calf (mean, 2.5) and in the anterior, posterior and lateral compartments of the distal calf (2.6, 2.8 and 2.5). Comparing right and left legs showed that there was visible asymmetry, which was not statistically significant. There was considerable variation in the pattern of involvement from patient to patient. The fact that all four calf muscle compartments may be involved asymmetrically and in varying degrees is important for treatment planning, including surgery. Not all patients have the classic symmetrical peroneal pattern of denervation.

CT and MR imaging of the pediatric orbit.

Orbital abnormalities encountered in the pediatric population differ substantially from those found in adult patients. Retinoblastoma, the most serious intraocular tumor, is often difficult to diagnose, but use of computed tomography (CT) (which reveals the characteristic focal calcification) and magnetic resonance (MR) imaging allows this tumor to be differentiated from pseudogliomas, such as Coats disease, and retrolental fibroplasia. CT and MR imaging help in the differentiation of orbital cellulitis from preseptal, lacrimal, and eyelid infectious processes and of orbital pseudotumor from Graves disease. In cases of orbital trauma, CT is excellent for detecting orbital fractures and metallic foreign bodies; MR imaging is better for depicting ocular and optic nerve injuries. Both modalities allow the differentiation of rhabdomyosarcoma from dermoid, cavernous hemangioma, and lymphangioma and provide helpful information for the diagnosis of many other tumors. Since CT and MR imaging have widely expanded the capabilities of orbital imaging, it is more important than ever before for radiologists to understand pediatric orbital disease.

Sarcoidosis of the CNS: comparison of unenhanced and enhanced MR images.

Sarcoidosis involving the CNS has a predilection for the leptomeninges, although parenchymal involvement occurs. We retrospectively evaluated the appearance of CNS sarcoidosis on unenhanced and enhanced MR images. MR studies were abnormal in 17 of 20 patients with CNS sarcoidosis. In all 17 patients, meningeal disease was detected on the gadopentetate-dimeglumine-enhanced T1-weighted images; the disease was detected on unenhanced images in three patients. Well-defined leptomeningeal patterns of enhancement were present in 15 patients. Other areas of involvement were the dura; brain parenchyma including hypothalamus, periventricular white matter, and ventricular ependyma; optic chiasm; and pituitary gland. Gadopentetate dimeglumine optimally evaluates meningeal disease and highlights the importance of the leptomeninges and Virchow-Robin spaces in the pathogenesis of CNS sarcoidosis. Enhanced MR is the preferred imaging technique for the evaluation of CNS sarcoidosis.

MR imaging of CSF-like choroidal fissure and parenchymal cysts of the brain.

The purposes of this study were to delineate the MR characteristics of CSF-like parenchymal or fissural cysts of the brain and to correlate them with the clinical findings. Clinical data and MR images of 34 patients with these abnormalities were reviewed. Pathologic correlation was not available. Two types of cystic lesions were identified and separated by location: medial temporal lobe cysts arising in or near the choroidal fissure (26 patients) and parenchymal or pseudoparenchymal cysts not related to the choroidal fissure (eight patients). The choroidal fissure cysts simulated intraparenchymal cysts on axial images but their extraaxial location was well portrayed on the coronal images. Choroidal fissure cysts had a characteristic spindle shape on sagittal images. The other cysts were found in the temporal lobe (seven patients) or thalamus (one patient) and appeared parenchymal but situated close to the subarachnoid space. These lesions were round or ovoid. There was no abnormal enhancement in 10 patients studied with gadopentetate dimeglumine. Coronal images were most useful, revealing the cysts as focal CSF-intensity lesions expanding the choroidal fissure of the temporal lobe. All the cysts appeared to represent incidental findings that did not correlate with the clinical signs and/or symptoms that prompted the imaging evaluations. The MR characteristics of CSF-like cysts are important to recognize so that they are not confused with other, more serious entities, such as intraaxial cystic tumors, infarctions, or parasitic lesions.

Sarcoidosis of the CNS: comparison of unenhanced and enhanced MR images.

Sarcoidosis involving the CNS has a predilection for the leptomeninges, although parenchymal involvement occurs. We retrospectively evaluated the appearance of CNS sarcoidosis on unenhanced and enhanced MR images. MR studies were abnormal in 17 of 20 patients with CNS sarcoidosis. In all 17 patients, meningeal disease was detected on the gadopentetate-dimeglumine-enhanced T1-weighted images; the disease was detected on unenhanced images in three patients. Well-defined leptomeningeal patterns of enhancement were present in 15 patients. Other areas of involvement were the dura; brain parenchyma including hypothalamus, periventricular white matter, and ventricular ependyma; optic chiasm; and pituitary gland. Gadopentetate dimeglumine optimally evaluates meningeal disease and highlights the importance of the leptomeninges and Virchow-Robin spaces in the pathogenesis of CNS sarcoidosis. Enhanced MR is the preferred imaging technique for the evaluation of CNS sarcoidosis.

MR imaging of CSF-like choroidal fissure and parenchymal cysts of the brain.

The purposes of this study were to delineate the MR characteristics of CSF-like parenchymal or fissural cysts of the brain and to correlate them with the clinical findings. Clinical data and MR images of 34 patients with these abnormalities were reviewed. Pathologic correlation was not available. Two types of cystic lesions were identified and separated by location: medial temporal lobe cysts arising in or near the choroidal fissure (26 patients) and parenchymal or pseudoparenchymal cysts not related to the choroidal fissure (eight patients). The choroidal fissure cysts simulated intraparenchymal cysts on axial images but their extraaxial location was well portrayed on the coronal images. Choroidal fissure cysts had a characteristic spindle shape on sagittal images. The other cysts were found in the temporal lobe (seven patients) or thalamus (one patient) and appeared parenchymal but situated close to the subarachnoid space. These lesions were round or ovoid. There was no abnormal enhancement in 10 patients studied with gadopentetate dimeglumine. Coronal images were most useful, revealing the cysts as focal CSF-intensity lesions expanding the choroidal fissure of the temporal lobe. All the cysts appeared to represent incidental findings that did not correlate with the clinical signs and/or symptoms that prompted the imaging evaluations. The MR characteristics of CSF-like cysts are important to recognize so that they are not confused with other, more serious entities, such as intraaxial cystic tumors, infarctions, or parasitic lesions.

NIH conference. Neurofibromatosis 1 (Recklinghausen disease) and neurofibromatosis 2 (bilateral acoustic neurofibromatosis). An update.

The neurofibromatoses comprise at least two autosomal dominant disorders affecting an estimated 100,000 Americans with clinical manifestations that may require care from every type of clinician. Neurofibromatosis 1 and neurofibromatosis 2 have in common the occurrence of many neurofibromas but are distinctly different clinical disorders. The disease genes are on different chromosomes. Magnetic resonance imaging, particularly with gadolinium enhancement, has generally supplanted other techniques for visualizing brain, spinal, and other neural tumors in both disorders. The technique has rekindled the controversy over the nature and frequency of optic pathway tumors in patients with neurofibromatosis 1 and has revealed, throughout the brains of young patients, bright lesions that have uncertain clinical consequences and unknown pathologic bases. In patients with neurofibromatosis 2, small acoustic neuromas can be seen, leading to the possibility of excision with preservation of hearing and facial nerve function. Abnormal hearing may occur to excess in patients with neurofibromatosis 1, but acoustic neuroma has never been documented. In patients with neurofibromatosis 2, a battery of audiologic tests has a high positive predictive power. Lisch nodules or iris hamartomas, probably a universal sign in adults with the neurofibromatosis 1 gene, cause no problem with vision. Posterior capsular lens opacity in patients with neurofibromatosis 2 is a helpful diagnostic sign and a potential source of additional handicap in persons at risk for impaired hearing. Progress in the clinical delineation of the disorders has been matched with considerable research into the still obscure pathogenesis of the disorders. Such rapid advances may necessitate reconsideration of the conclusions of the National Institutes of Health Consensus Development Conference on Neurofibromatosis, especially those on the categories of persons in which a neurofibromatosis should be considered and the need for caution in recommending surgery. Watchful waiting may often be the best management for acoustic neuromas in neurofibromatosis 2.

Measurements of the normal cervical spinal cord on MR imaging.

The purpose of this study was to determine normal measurements of the C1-T3 spinal cord in anteroposterior and transverse planes from MR images and to compare these with previously published data. Seven hundred and fifty-six measurements were made from 66 randomly selected MR studies of the cervical spine. We measured the anteroposterior and transverse diameters of the cord at each vertebral level and computed the simple product of these diameters to provide a single useful numerical value, termed the approximate cord area (ACA). The cord varies in average anteroposterior and transverse diameters from 8.8 mm x 12.4 mm at C2 to 8.7 mm x 14 mm at C4 to 7.4 mm x 11.4 mm at C7. The cervical enlargement was found from C4 to C6 and was most evident by comparing the ACA values. At C2 the average ACA was 110 mm2, at C4 it was 121.9 mm2, and at C7 the average ACA was 84.6 mm2. Comparison of our data with the literature reveals disparate measurements that vary up to 6 mm from our mean values. However, our results correlated well with the postmortem studies of Nordquist (1964). A single number cannot be used as the basis for evaluating spinal cord size. Each level should be compared with the normal range specific for that level.

MRI and neuropsychological correlates of dementia in Binswanger's disease.

Nuclear magnetic resonance imaging (MRI) has facilitated diagnosis of Binswanger's disease in vivo, which has proven to be a more common disease entity than once believed. These patients generally present with hypertension, progressive dementia, hydrocephalus, gait difficulty, and personality change. A patient is presented with MRI findings of white-matter destruction and subcortical lesions, and with neuropsychological findings of higher-order cognitive impairment but selectively preserved language and visuospatial-perceptual skills. The relationship between the patient's cognitive-behavioral symptoms and the presence of disconnection syndrome is discussed. In addition, the utility of neuropsychological examination is reviewed. Finally, implications for differentiating cortical from subcortical dementia with psychometric test data are discussed.

The association of posterior capsular lens opacities with bilateral acoustic neuromas in patients with neurofibromatosis type 2.

This study of 47 patients from 11 families with neurofibromatosis type 2 (NF 2) confirms our previously reported association between posterior capsular cataract and NF 2. A highly significant statistical association was found between the presence of posterior capsular lens opacities and the presence of NF 2 as determined by magnetic resonance imaging or pathologic diagnosis. This association was not present for other types of lens opacities that could be the result of age-related or nonspecific changes. When considering the diagnosis of NF 2, this finding now makes it essential to use a careful dilated biomicroscopic examination of the lens to evaluate known, suspected, or at-risk individuals for this potentially early associated manifestation.