Transcranial ultrasound focus reconstruction with phase and amplitude correction

Therapeutic and diagnostic ultrasound procedures performed noninvasively through the skull require a reliable method for maintaining acoustic focus integrity after transmission through layered bone structures. This study used a multiple-element, phased-array transducer to reconstruct ultrasound foci through the human skull by amplitude and phase correction. It was previously demonstrated that adaptive phase correction using a multiple-element, focused transducer array yields a significant correction to an acoustic field that has been distorted by the heterogeneities of the skull bone. The introduction of amplitude correction, in a regime in which acoustic pressures from individual transducer array elements are adjusted to be normalized at the focus, has demonstrated a 6% (-0.27 dB) average decrease in acoustic sidelobe acoustic intensity relative to the focal intensity and a 2% (-0.09 dB) average decrease in the full-width-at-half-maximum (FWHM) of the acoustic intensity profile at the focus. These improvements come at the expense of significant ultrasound intensity loss--as much as 30% lower (-1.55 dB)--at the focus because the amplitude correction method requires that, at constant power, a larger proportion of energy is absorbed or reflected by regions of the skull that transmit less energy. In contrast, a second correction method that distributes pressure amplitudes such that the sections of the skull which transmit more ultrasound energy are exposed with higher ultrasound intensities has demonstrated an average sidelobe intensity decrease of 3% (-0.13 dB) with no change in the FWHM at the focus. On average, there was a 2% (0.09 dB) increase in the acoustic intensity at the focus for this inverse amplitude correction method. These results indicate that amplitude correction according to the transmission properties of various segments of the skull have a clear effect on ultrasound energy throughput into a target site within the brain parenchyma.     

Effect of potassium and sodium carbonate catalysts on the rate of gasification of metallurgical coke

The catalytic effects of potassium and sodium carbonates on the rate of gasification of metallurgical coke with carbon dioxide have been investigated by the thermogravimetric method. The experiments were carried out using metallurgical coke fines mixed with 5 wt% catalyst, the mixture pressed into disc-shaped pellets from which a small specimen (23 mg) was cut and used. The reaction was carried out at temperatures ranging from 725 to 900°C using pure CO₂ at 1 atm.The rates were measured for uncatalyzed coke-CO₂ reaction and with K₂CO₃, Na₂CO₃ and mixed (K, Na)₂CO₃ catalysts. Potassium carbonate exhibited the greatest catalytic activity closely followed by the mixed catalyst and sodium carbonate. For the K₂CO₃-catalyzed reaction, an activation energy of 41.74 (±3.13) kcal/mole was found; and for the Na₂CO₃-catalyzed reaction the figure was 40.27 (± 5.05) kcal/mole.The catalysis is thought to occur by the “vapor cycle” mechanism. It consists of reduction (M₂CO₃→2M) followed by oxidation (2M → M₂CO₃). When CO₂ is present in the system the alkali vapor (M) quickly gets reconverted to the carbonate.     

Efficacy and onset of action of fluticasone propionate aqueous nasal spray on nasal symptoms, eosinophil count, and mediator release after nasal allergen challenge in patients with seasonal allergic rhinitis

In order to determine if peripheral blood stem cells (PBSC) collected after priming with G-CSF in AML in first complete remission (CR) can be used for autologous transplantation and to evaluate the efficacy of early intensification therapy as in vivo purging, we studied 35 consecutive patients with AML in first CR. After standard induction and consolidation chemotherapy, 24 of them were treated with one (10 patients) or two (14 patients) cycles of high-dose cytarabine plus etoposide prior to PBSC collection. G-CSF was used as the priming agent. Of the 35 patients scheduled for peripheral blood stem cell transplantation (PBSCT), three relapsed before transplantation, and the 32 remaining underwent PBSCT. High-dose therapy consisted of either total body irradiation plus cyclophosphamide or busulphan plus cyclophosphamide. The median number of CD34+ cells infused was 3.24 x 10(6)/kg (range 0.15-14). The median times to reach a PMN count of 0.5 x 10(9)/l and a platelet count of 50 x 10(9)/l were 12 (8-28) and 30 (11-345) days, respectively. There was no transplant-related mortality. Twelve patients relapsed between 2 and 21 months post-PBSCT. With a median follow-up of 28 months, actuarial disease-free survival (DFS) is 52.41 +/- 9% in the intent-to-treat group and 57.4 +/- 9.8% in patients who underwent PBSCT. The probability of DFS is significantly higher for patients who receive early intensification therapy prior to both PBSC collection and PBSCT as compared with patients that do not: 68.8 +/- 10.27% vs 35.5 +/- 12.6%, P = 0.0418. These results indicate the feasibility of PBSCT in AML using G-CSF-mobilized PBSC. The use of intensification treatment as 'purging in vivo' prior both to collection of PBSC and PBSCT significantly reduces the risk of relapse in this group of patients.     

选择合适的无线技术(一):频谱、通信距离和网络拓扑

当今有许多不同的无线标准和协议在使用,要为任何特定的应用选择合适的技术可能很困难.在这篇文章中,我们将探讨一些需要考虑的关键标准,并评介四个流行的选项:Wi-Fi?技术(无线保真)、蓝牙低功耗(Bluetooth? Low Energy)技术、专有射频(RF)和来自连接性标准联盟(Connectivity Standa...     

Collagenase-aided intracortical microelectrode array insertion: effects on insertion force and recording performance

Intracortical microelectrodes puncture the intact pia mater membrane during insertion, a process that can cause brain dimpling and trauma. To ensure that the device is able to withstand forces during implantation without buckling, the selection of acceptable implant materials and geometries is limited to rigid designs with large cross-sectional areas. Such designs likely increase insertion trauma and potentially exacerbate the chronic tissue response. In this paper, a technique that may relax the mechanical requirements of implanted microelectrodes through enzymatic (collagenase mediated) manipulation of the pia mater is quantified experimentally. Measurements of the insertion force profiles were obtained with a load cell during computer controlled ($10 mu$ m/s) insertion of microwire arrays into the cortex of rats. It was observed that collagenase application reduced the peak insertion force experienced by the microwire arrays by almost 40% on average ( $4.04 pm hbox{2.03}$ mN versus $2.36 pm hbox{1.17}$ mN; control versus treated sites). Peak insertion force magnitudes were highly dependent on implant location with anterior sites registering lower peaks than more posterior sites. Chronic neural recording performance (up to one month) did not appear to be adversely affected by the collagenase treatment, suggesting the overall safety of the technique. Our data suggest that controlled application of collagenase is a useful method in enabling implantation of thinner microelectrodes, potentially facilitating reduced insertion trauma and lower immune response. Furthermore, due to dependence of insertion force on anatomical location, the intended target region should be considered in implant design.      

Aluminum nitride for heatspreading in RF IC’s

To reduce the electrothermal instabilities in silicon-on-glass high-frequency bipolar devices, the integration of thin-film aluminum nitride as a heatspreader is studied. The AlN is deposited by reactive sputtering and this material is shown to fulfill all the requirements for actively draining heat from RF IC’s, i.e., it has good process compatibility, sufficiently high thermal conductivity and good electrical isolation also at high frequencies. The residual stress and the piezoelectric character of the material, both of which can be detrimental for the present application, are minimized by a suitable choice of deposition conditions including variable biasing of the substrate in a multistep deposition cycle. Films of AlN as thick as 4 μm are successfully integrated in RF silicon-on-glass bipolar junction transistors that display a reduction of more than 70% in the value of the thermal resistance.     

Reducing the Number of Comparators in Multibt $Delta Sigma $ Modulators

Multibit feedback, being one way of lowering DeltaSigma modulators power consumption, has a major obstacle: the number of components in the internal analog-to-digital converter (ADC) and digital-to-analog converter (DAC). Nevertheless, the number of comparators in the ADC can be significantly reduced depending on the order of noise-shaping and the oversampling ratio. In this paper, we propose an auto-ranging algorithm with a mechanism to keep the structure stable that emulates more quantization levels than that allowed by the number of comparators. As the recourse to segmented DACs allows lowering the complexity of the mismatch shaping encoder, the auto-ranging ADC brings the benefits of multibit feedback without the usual increase in size and power consumption. The internal number of bits in DeltaSigma modulators is no more restricted by the difficulty of building the flash ADC with a low voltage supply.