Detonation synthesis of carbon nano-onions via liquid carbon condensation.

Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by high-resolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures.

Use of small-angle X-ray scattering to resolve intracellular structure changes of Escherichia coli cells induced by antibiotic treatment.

The application of small-angle X-ray scattering (SAXS) to whole Escherichia coli cells is challenging owing to the variety of internal constituents. To resolve their contributions, the outer shape was captured by ultra-small-angle X-ray scattering and combined with the internal structure resolved by SAXS. Building on these data, a model for the major structural components of E. coli was developed. It was possible to deduce information on the occupied volume, occurrence and average size of the most important intracellular constituents: ribosomes, DNA and proteins. E. coli was studied after treatment with three different antibiotic agents (chloramphenicol, tetracycline and rifampicin) and the impact on the intracellular constituents was monitored.

Electronic structure differences between H(2)-, Fe-, Co-, and Cu-phthalocyanine highly oriented thin films observed using NEXAFS spectroscopy.

Phthalocyanines, a class of macrocyclic, square planar molecules, are extensively studied as semiconductor materials for chemical sensors, dye-sensitized solar cells, and other applications. In this study, we use angular dependent near-edge x-ray absorption fine structure (NEXAFS) spectroscopy as a quantitative probe of the orientation and electronic structure of H2-, Fe-, Co-, and Cu-phthalocyanine molecular thin films. NEXAFS measurements at both the carbon and nitrogen K-edges reveal that phthalocyanine films deposited on sapphire have upright molecular orientations, while films up to 50 nm thick deposited on gold substrates contain prostrate molecules. Although great similarity is observed in the carbon and nitrogen K-edge NEXAFS spectra recorded for the films composed of prostrate molecules, the H2-phthalocyanine exhibits the cleanest angular dependence due to its purely out-of-plane π* resonances at the absorption onset. In contrast, organometallic-phthalocyanine nitrogen K-edges have a small in-plane resonance superimposed on this π* region that is due to a transition into molecular orbitals interacting with the 3dx(2)-y(2) empty state. NEXAFS spectra recorded at the metal L-edges for the prostrate films reveal dramatic variations in the angular dependence of specific resonances for the Cu-phthalocyanines compared with the Fe-, and Co-phthalocyanines. The Cu L3,2 edge exhibits a strong in-plane resonance, attributed to its b1g empty state with dx(2)-y(2) character at the Cu center. Conversely, the Fe- and Co- phthalocyanine L3,2 edges have strong out-of-plane resonances; these are attributed to transitions into not only b1g (dz(2)) but also eg states with dxz and dyz character at the metal center.

Three-dimensional coherent x-ray diffraction imaging of a ceramic nanofoam: determination of structural deformation mechanisms.

Ultralow density polymers, metals, and ceramic nanofoams are valued for their high strength-to-weight ratio, high surface area, and insulating properties ascribed to their structural geometry. We obtain the labrynthine internal structure of a tantalum oxide nanofoam by x-ray diffractive imaging. Finite-element analysis from the structure reveals mechanical properties consistent with bulk samples and with a diffusion-limited cluster aggregation model, while excess mass on the nodes discounts the dangling fragments hypothesis of percolation theory.

Monochromatic electron photoemission from diamondoid monolayers.

We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays.

Molecular limits to the quantum confinement model in diamond clusters.

The electronic structure of monodispersed, hydrogen-passivated diamond clusters (diamondoids) in the gas phase has been studied with x-ray absorption spectroscopy. The data show that the bulk-related unoccupied states do not exhibit any quantum confinement. Additionally, density of states below the bulk absorption edge appears, consisting of features correlated to CH and CH2 hydrogen surface termination, resulting in an effective redshift of the lowest unoccupied states. The results contradict the commonly used and very successful quantum confinement model for semiconductors, which predicts increasing band edge blueshifts with decreasing particle size. Our findings indicate that in the ultimate size limit for nanocrystals a more molecular description is necessary.

High-performance liquid chromatographic method for the quantitative determination of butorphanol, hydroxybutorphanol, and norbutorphanol in human urine using fluorescence detection.

A sensitive, quantitative reversed-phase high-performance liquid chromatographic method has been established for the simultaneous determination of butorphanol, a synthetic opioid, and its metabolites, hydroxybutorphanol and norbutorphanol, in human urine samples. The method involved extraction of butorphanol, hydroxybutorphanol, and norbutorphanol from urine (1.0 ml), buffered with 0.1 ml of 1.0 M ammonium acetate (pH 6.0), onto 1-ml Cyano Bond Elut columns. The eluent was evaporated under nitrogen and low heat, and reconstituted with the HPLC mobile phase, acetonitrile-methanol-water (20:10:70, v/v/v), containing 10 mM ammonium acetate and 10 mM TMAH (pH 5.0). The samples were chromatographed on a reversed-phase octyl 5-microns column. The analysis was accomplished by detection of the fluorescence of the three analytes, at excitation and emission wavelengths of 200 nm and 325 nm, respectively. The retention times for hydroxybutorphanol, norbutorphanol, the internal standard, and butorphanol were 5.5, 9.0, 13.0, and 23.4 min respectively. The validated quantitation range of the method was 1-100 ng/ml for butorphanol and hydroxybutorphanol, and 2-200 ng/ml for norbutorphanol in urine. The observed recoveries for butorphanol, hydroxybutorphanol, and norbutorphanol were 93%, 72%, and 50%, respectively. Standard curve correlation coefficients of 0.995 or greater were obtained during validation experiments and analysis of study samples. The method was applied on study samples from a clinical study of butorphanol, providing a pharmacokinetic profiling of butorphanol.

High-performance liquid chromatographic procedure for the quantitative determination of paclitaxel (Taxol) in human plasma.

An isocratic high-performance liquid chromatographic method has been developed and validated for the quantitative determination of paclitaxel (Taxol), a novel antimitotic, anticancer agent, in human plasma. The analysis required 0.5 ml of plasma, and was accomplished by detection of the UV absorbance of paclitaxel at 227 nm following extraction and concentration. The method involved extraction of paclitaxel from plasma, buffered with 0.5 ml of 0.2 M ammonium acetate (pH 5.0), onto 1-ml cyano Bond Elut columns. The eluent was evaporated under nitrogen and low heat, and reconstituted with the mobile phase, acetonitrile-methanol-water (4:1:5, v/v/v) containing 0.01 M ammonium acetate (pH 5.0). The samples were chromatographed on a reversed-phase octyl 5 microns column. The retention time of paclitaxel was 10 min. The validated quantitation range of the method was 10-1000 ng/ml (0.012-1.17 microM) of paclitaxel in plasma. Standard curve correlation coefficients of 0.995 or greater were obtained during validation experiments and analysis of clinical study samples. The observed recovery for paclitaxel was 83%. Epitaxol, a biologically active stereoisomer, and baccatin III, a degradation product, were also chromatographically separated from taxol by this assay. The method was applied to samples from a clinical study of paclitaxel in cancer patients, providing a pharmacokinetic profiling of paclitaxel.

EEG frequency patterns in the cat prepyriform cortex during sleep and waking.

The cellular populations in the prepyriform cortex are a primary processing station for sensory information from the olfactory bulb. These populations are also influenced from forebrain and other brain systems involved in behaviour. Recording electrodes can be precisely placed in this cortex compared to many other brain structures. This permits straddling the cortical superficial pyramidal cell layer with a bipolar recording configuration and the ability to obtain information about awake-vigilant and other state conditions from this brain structure. Methadone, a vigorously arousing drug in the cat, and a short acting barbiturate was administered to compare the differences of EEG patterns obtained during normal awake and sleep conditions. Fourier analysis was used in this study and combined with computer profiles of spectra to show time relationships of the state conditions in the cortex. Good separation of the spectra, between the major states in the cat, were observed using this technique for both natural and drug-induced changes.

Effects of ethanol on eye movements in the monkey.

Ethanol (0.25-2.0 g/kg) was administered by remotely controlled intravenous infusion to monkeys engaged in performance of a short-term memory task which required attention to and retention of visual stimuli. Eye movements were monitored and measured by recording the electrooculogram with implanted periorbital Ag/AgCl electrodes. Ethanol induced the following dose-dependent changes of ocular motility: (a) diminution of the frequency of saccades; (b) prolongation of fixation (immobility) periods, though stimulus-elicited fixations became shorter; (c) increase in saccade excursion; (d) increase in saccade duration; and (e) decrease in saccade velocity (preceded at low doses by a transient increase). These changes were correlated with an impairment of behavioral performance. The results of eye movement analysis complement the results obtained on studies of human subjects by oral administration of ethanol. The findings of the present study in the nonhuman primate are interpreted as a reflection of the deleterious effects of alcohol on the cerebral substrate of visual attention.

The principal projection pathway between the olfactory bulb and the prepyriform cortex in the cat.

The anatomy and neuroelectric properties of the lateral olfactory tract (LOT) were investigated in the cat. Electron micrographs were obtained from sampled areas across the rostro-caudal projection of the pathway. Fiber diameters were estimated and axon spectra were obtained from three regions corresponding to peduncle, mid-LOT, and caudal-LOT. The mean inside diameter for all measured axons was 1.13 +/- 0.53 microns. The greatest number was found in the peduncle (approximately 600,000 axons). Mid-LOT and caudal-LOT each contained approximately 250,000 axons. Unmyelinated processes were estimated to be more numerous than the myelinated axons. Synaptic structures were also observed in the LOT. Cross-sectional area measurements of the LOT were obtained from tissue prepared for light microscopy. The area decreased from about 0.3 to 0.2 mm2 across the projection from olfactory bulb to cortex. The anatomical data were used to predict the conduction properties of transmission over the LOT. The olfactory bulb mitral cells were stimulated electrically and conduction velocity and temporal dispersion were evaluated in the tract. The strength-duration and stimulus-response curves and the potential profile during stimulation were also obtained. The time constant for LOT axons was 0.3 msec. The stimulus-response curve was sigmoidal in shape for both presynaptic and postsynaptic responses. The relationship between input (the action potentials) and output (cortical postsynaptic potentials) was linear up to 90 times threshold. Action potentials were conducted at 20 m/sec across the pathway over the peduncle and decreased to about 10 m/sec in caudal aspects. The potential profile for action potentials decayed exponentially into the depths of the cortex whereas the synaptic potential was a surface negative dipole field. The axon spectra were convolved with the electrophysiological properties of the LOT to mathematically reconstruct action potentials. The empirically derived mono- and biphasic curves fitted reasonably well with experimentally derived data under various stimulus conditions.

Effects of ethanol on visual evoked responses in monkeys performing a memory task.

The effects of ethanol on behavior and visual evoked potentials were investigated in monkeys performing a visual short-term memory task. Ethanol induced a dose-dependent deficit in performance and a prolongation of visuo-motor reaction time. The normal patterns of ocular motility were concomitantly altered. The potentials elicited in the lateral geniculate nucleus, the striate cortex, the inferotemporal cortex, the amygdala, and the mesencephalic reticular formation by a colored stimulus used by the animal in the task were attenuated by the alcohol in dose-related manner. In contrast, potentials elicited in the striate cortex and reticular formation by a brief and diffuse flash were augmented under the influence of the substance. It is inferred that ethanol can increase the reactivity of reticular and cortical structures to undifferentiated stimuli, while at the same time interfering with the basic mechanisms of visual attention and perception.

Principal component analysis of evoked responses and the effects of alcohol on the geniculo-striate system of the monkey.

This study was designed to test the effects of alcohol on visual evoked potentials in nonhuman primates performing a cognitive task. Flash evoked potentials were recorded from monkeys involved in a delayed matching-to-sample (DMS) paradigm in which the flash served as an alerting signal before each trial. Event-related potentials were recorded from the lateral geniculate nucleus and homolateral striate cortex before, during, and after intravenous administration of saline or ethanol (0.25, 0.5, 1.0, and 2.0 g/kg). Average evoked potentials (AEPs) were computed. Residual waveforms were obtained by subtracting the predrug AEP from postdrug AEPs. A principal component analysis was employed to define the alcohol alterations on the evoked responses. In the analysis each AEP was represented by 40 time points spaced 12 msec apart. These reduced representations of the AEP were entered in the variance-covariance matrix calculations. The first five eigenvectors were computed and plotted. Alcohol produced the greatest variance in the AEPs at the two highest dose levels. So the data were grouped together into three experimental categories: saline, low-dose (0.25-0.5 g/kg) and high-dose (1.0-2.0 g/kg). A correlation template, representing each category, was computed by correlating individual eigenvectors with each sequential average composed of 10 individual evoked potentials in the 200 trials of an experimental session. Alcohol affected the state vector from the brain by loading the correlation coefficient in the opposite direction following alcohol administration in two principal components. One or two of the eigenvectors significantly (P less than 0.01) shifted in geniculate nucleus, indicating that either the nucleus or a previous station was affected by alcohol. In comparison, three or more eigenvectors from striate cortex were shifted significantly following alcohol injection. This difference may be explained by the effect of alcohol on multisynaptic brain structures, including the brain-stem reticular formation, which in turn influenced the cortex.

The ultrastructure of the sheath around chronically implanted electrodes in brain.

Insulated, bipolar stainless steel electrodes were chronically implanted in various regions of the cat brain and the long-term structural changes in the tissue surrounding the electrodes were studied by light and electron microscopy. A sheath surrounded and separated the electrode from normal grey or white matter. A layer of foreign body giant cells of variable thickness was formed adjacent to the electrode. This layer was attenuated in some places so that it was unrecognizable by light microscopy. The bulk of the sheath structure consisted of collagen fibrils, leptomeningeal cells and hypertrophied astrocytes. Areas consisting of modified leptomeningeal cells with long thin processes we designated as spongy areas. These have not been previously reported using the electron microscope. Glycogen bodies were seen in leptomeningeal cells. Astrocytes became greatly enlarged and were more numerous in and around the sheath. Oligodendrocytes contained lamellar bodies, and direct continuity was shown between a lamellar body and an adjacent myelin sheath. Myelin was seen in abnormal sites (around oligodendrocytes and neurons) and in unusual configurations. Neuronal changes near the sheath included whorls and stacks of modified endoplasmic reticulum and the presence of cytoplasmic nucleolus-like bodies. Reactive, regenerative and degenerative axons were observed. Blood vessels were more numerous in the sheath and surrounding tissue than normal. Perivascular spaces were prominent even around capillaries and often plasma cells and monocytes were in these spaces. As compared to normal tissue the extracellular space is noticeably increased. Electrodes passing through ventricles were surrounded with a sheath covered with ependymal cells. This sheath was comparable in structure to the sheath present around the electrode in other locations.

Design for a micropowered multichannel PAM/FM biotelemetry system for brain research.

A design for a 12-channel pulse amplitude-modulated/FM biotelemetry system is described. The biotelemeter mounts on an animal's head close to the electrode probes to record and transmit brain electrical data. The size of the unit is 4.5 x 6.5 x 2 cm and it weighs about 60 g. It is designed to acquire EEG and other physiological data where the requirement is to obtain bioelectrical activity without cable encumbrance or confining behavioral restrictions. The telemeter consumes about 800 muW of power and operates for approximately 3 continous days before it is necessary to exchange the utilization of complementary metal oxide semiconductor (CMOS) integrated circuits. Transmission range is typically about 10 m.

Medial reticular and perihypoglossal neurons projecting to cerebellum.

Almost 10% of neurons in the medial reticular nucleus or adjacent thereto were invaded antidromically in response to stimulation of the fastigial and interpositus nuclei. The fraction was 77/835 for the bulbar and caudal pontine levels, but 0/167 for rostral pontine levels. The mahority, 49, of the neurons projecting to the cerebellum were superficially located in the region of the perihypoglossal nucleus, but 23 were scattered through the medial reticular nucleus, being 2.5-5.0 mm below the bulbopontine dorsum. Both classes of cerebellopetal neurons had a similar range of antidromic latencies, usually from 0.8 to 2.0 ms, but some were ober 3 ms. Both classes responded to volleys from limb nerves and inputs from cutaneous mechanoreceptors, with ranges of excitatory and inhibitory latencies that were similar to those for other medial reticular neurons. It is conjectured that the axonal projection is primarily to the cerebellar cortex and that the branches to the nuclei are often slender, hence the long antidromic latencies; 31 of 59 neurons tested projected to cerebellar nuclei on both sides, often with a considerable latency differential. Rarely, there were also axonal branches projecting up the central tegmental tract. The experimental findings are in very good accord with the anatomical descriptions of Brodal and associates (4, 5, 8, 19). It is suggested that the paramedian reticular and the perihypoglossal nuclei may provide a background excitatory input to the interpositus nuclei.