Effects of External Auditory Meatus Occlusion on Ocular Vestibular Evoked Myogenic Potentials Induced by Bone Conducted Sound

To facilitate more reliable recordings of the ocular vestibular evoked myogenic potentials (oVEMP) induced by bone-conducted sound using the B81 bone conduction transducer, we preliminarily studied the effects of external auditory meatus occlusion using an earplug on such oVEMP. Eight healthy volunteers (four males and four females, 26–48 years of age, mean age: 34. 5 years) and 14 patients with vestibular disease (2 males and 12 females, 18–59 years of age, mean age: 41.5 years) were enrolled. oVEMP testing was performed using a B81 placed on the temple. Tone bursts (500 Hz, rise/fall time: 2 ms, plateau time: 2 ms, and 70 dB nHL) were presented at a rate of 5.1 Hz. N1-P1 amplitudes were measured and analyzed. Occlusion resulted in significantly larger N1-P1 amplitudes [mean ± SE (SD): 12.3 ± 1.67 (6.71) μV vs. 9.55 ± 1.55 (6.21) μV; p = 0.020, paired t-test]. While four patients did not exhibit any response on either side in the absence of occlusion, all of them showed unilateral or bilateral responses when occlusion was employed. In any patient occlusion did not result in loss of oVEMP responses. External auditory meatus occlusion using an earplug could allow more reliable recordings of bone conduction transducer-induced oVEMP.

Breast dynamic contrast enhanced MRI: fibrocystic changes presenting as a non-mass enhancement mimicking malignancy

Background We aimed to analyse the morphokinetic features of breast fibrocystic changes (nonproliferative lesions, proliferative lesions without atypia and proliferative lesions with atypia) presenting as a non-mass enhancement (NME)in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) examination. Patients and methods Forty-six patients with histologically proven fibrocystic changes (FCCs) were retrospectively reviewed, according to Breast Imaging Reporting and Data System (BI-RADS) lexicon. Prior to DCE-MRI examination, a unilateral breast lesion suspicious of malignancy was detected clinically, on mammography or breast ultrasonography. Results The predominant features of FCCs presenting as NME in DCE-MRI examination were: unilateral regional or diffuse distribution (in 35 patients or 76.1%), heterogeneous or clumped internal pattern of enhancement (in 36 patients or 78.3%), plateau time-intensity curve (in 25 patients or 54.3%), moderate or fast wash-in (in 31 patients or 67.4%).Nonproliferative lesions were found in 11 patients (24%), proliferative lesions without atypia in 29 patients (63%) and lesions with atypia in six patients (13%), without statistically significant difference of morphokinetic features, except of the association of clustered microcysts with proliferative dysplasia without atypia. Conclusions FCCs presenting as NME in DCE-MRI examination have several morphokinetic features suspicious of malignancy, therefore requiring biopsy (BI-RADS 4). Nonproliferative lesions, proliferative lesions without atypia and proliferative lesions with atypia predominantly share the same predefined DCE-MRI morphokinetic features.

Effects of Annealing Parameters on Nickel Catalyst Nanoparticle Size for Carbon Nanotube Synthesis Applications

The properties of carbon nanotubes are dependent, in part, on the size of the catalyst metal nanoparticles from which the carbon nanotubes are grown. Annealing is a common technique for forming the catalyst nanoparticles from deposited films. While there is ample work connecting catalyst film properties or catalyst nanoparticle properties to carbon nanotube growth outcomes, the control of catalyst nanoparticle size by means other than the variation of initial film thickness is less explored. This work develops an empirical correlation for the control of nickel nanoparticle equivalent diameter by modification of anneal plateau temperature and anneal plateau time, thereby providing an additional avenue of control for catalyst properties. It has been hypothesized that the size of catalyst nanoparticles can be predetermined by appropriate selection of the initial catalyst film thickness, plateau temperature, and plateau time of the annealing process. To this end, buffer layers of 50 nm titanium, followed by 20 nm aluminum, were deposited onto silicon substrates via electron beam evaporation. Nickel catalyst layers were then deposited with thicknesses of either 5, 10, or 20 nm. Samples of each of the three nickel layer thicknesses were annealed in an ambient air environment at different combinations of 500, 600, 700, 800, and 900 °C plateau temperature and 5, 10, and 15 minute plateau time. Representative time-temperature curves corresponding to each plateau temperature were also acquired. The end result was a set of 45 samples, each with a unique combination of initial nickel film thickness, anneal plateau temperature, and anneal plateau time. Resulting nanoparticles were characterized by atomic force microscopy, and distributions of nanoparticle equivalent diameter were collected via a watershed algorithm implemented by the Gwyddion software package. Comparison of the 45 parameter combinations revealed a wide range of nanoparticle sizes. In most cases, comparable equivalent diameters were obtained from a variety of parameter combinations. Thus, results provide multiple options for achieving the same nanoparticle diameter, for use in cases where additional restraints are present. To facilitate such decisions, a correlation was developed that connected catalyst nanoparticle diameter to the three process parameters of initial catalyst film thickness, anneal plateau temperature, and anneal plateau time. For example, a given initial Ni film thickness can be annealed to a specified nanoparticle size by selecting anneal plateau temperature and plateau time per the correlation, provided that comparable buffer layers were chosen. This correlation provides a more robust array of options for specification of catalyst nanoparticle size and final carbon nanotube properties for a specific application.

Effect of transition section between the main switch and middle cylinder of Blumlein pulse forming line on the diode voltage of intense electron-beam accelerators

The rise-time of the pulse on the diode of the intense electron-beam accelerators (IEBA) is one of the important factors that affect the quality and characteristic of the output beam current of the IEBA. In this paper, effect of the transition section between the main switch and middle cylinder of strip spiral Blumlein line (SSBL) on the diode voltage of IEBA is analyzed in theory, based on the theoretical analysis of the wave propagation along the Blumlein pulse forming line (BPFL), the traveling time of the transition section has a great effect on the rise-time, the plateau-time, and the fall-time of the output voltage at the matching load. Furthermore, the operation of the whole accelerator consisting of the primary energy-storage capacitor, the Tesla transformer, a main switch, the transition section, BPFL, and a resistive load was simulated using a circuit-simulation code called PSpice, and the dependence of the output voltage on the inductance of the main switch and the transition section was obtained. It was found from the wave propagation theory and the circuit simulation using computer results that the wave traveling time of the transition section between the main switch and the middle cylinder of the SSBL influences considerably the rise-time, plateau-time, and fall-time of the voltage waveform at the matching load. In order to get an ideal square pulse voltage waveform at the matching load and to improve the electron beam quality of such an accelerator, the wave traveling time of the transition section should be designed as soon as possible. At last, a couple of contrastive experiments are performed on two kinds of IEBA. The experimental results agree with the theoretical analysis and simulated results.