The effects of maturation on early and late phases of phrenic neurogram during eupnea

In this paper, we investigate the effects of maturation on the early and late phases of the phrenic neurogram. We have used the matching pursuit (MP) method to examine the effects of maturation on breathing patterns in both time and frequency domains. The MP was chosen since the wavelet transform method may not represent signals whose Fourier transforms have a narrow high-frequency support. The phrenic neurogram was recorded from 25 piglets (3-35 days) during eupnea (normal breathing) at three postnatal age groups: young (3-7 days (n = 9)), (middle) 10-21 days (n = 6), and old (29-35 days (n = 10)). The energy percentage of atoms representing the nonperiodic neural activities (NPNAs) significantly decreased from young age to middle age groups (p<0.01) and from young age to old age groups (p<0.01), and from middle age to old age groups (p<0.055) in the early phase (the first half) of the phrenic neurogram, but these changes were not statistically significant in the late phase (the second half) of the phrenic neurogram as maturation proceeded. However, the energy percentage of atoms representing the periodic neural activities (PNAs) decreased with maturation, but these changes were not statistically significant in the early phase of the phrenic neurogram. The energy percentage of (PNAs) increased in the late phase of the phrenic neurogram as maturation proceeded although these changes were only significant between young and old age groups (p<0.01). These results suggest that the significant decrease of the NPNAs in the early phase and the increase in the late phase of the phrenic neurogram could be a sign of maturation in piglets.     

Influence of the vagus nerve on respiratory patterns during early maturation

Nonlinear dynamical analysis was performed on the phrenic neurogram before and after vagotomy in order to study the influence of the vagus nerve on the complexity of the phrenic neurogram in piglets in three age groups: 3-7 days (n = 7); 11-19 days (n = 6); and 29-34 days (n = 8). The phrenic neurogram, generated by the respiratory neural networks in the medulla, projects on the diaphragm muscles and initiate the respiratory movement. On the other hand, the vagus nerves carry the information from mechanoreceptors, located at the lower airway and lungs, to the medulla. The data was recorded during normal breathing (eupnea) before and after vagotomy while piglets were ventilated with 40% O2 in N2 and analyzed using the approximate entropy (ApEn) method. The mean values of the approximate entropy before and after vagotomy during the first 7 days of the postnatal age were 1.32 +/- 0.1 (standard deviation) and 1.34 +/- 0.07, respectively. These values before and after vagotomy during the 11-19 days age group were 1.15 +/- 0.09 and 1.12 +/- 0.05, respectively. For the 29-34 days age group, they were 1.14 +/- 0.05 before vagotomy and 1.19 +/- 0.08 after vagotomy. These differences in the ApEn (complexity) values of the phrenic neurogram before and after vagotomy are not statistically different at each age group. However, the mean mean approximate entropy (complexity) values between the 3-7 days age group and the other two groups were significantly different both before and after vagotomy (p < 0.05) using an analysis off variance test. These results suggest that the vagus nerve may not be mature during early maturation in piglets.     

A closed-loop mechanical ventilation controller with explicit objective functions

A closed-loop lung ventilation controller was designed, aiming to: 1) track a desired end-tidal CO2 pressure (Pet CO2), 2) find the positive end-expiratory pressure (PEEP) of minimum estimated respiratory system elastance (Ers,e), and 3) follow objective functions conjectured to reduce lung injury. After numerical simulations, tests were performed in six paralyzed piglets. Respiratory mechanics parameters were estimated by the recursive least squares (RLS) method. The controller incorporated a modified PI controller for Pet CO2 and a gradient descent method for PEEP. In each animal, three automated PEEP control runs were performed, as well as a manual PEEP titration of Ers,e and a multiple PetCO2 step change trial. Overall performance indexes were obtained from PEEP control, such as minimum Ers,e (37.0 +/- 4.5 cmH2O x L(-1)), time to reach the minimum Ers,e (235 +/- 182 s) and associated PEEP (6.5 +/- 1.0 cmH2O), and from Pet CO2 control, such as rise time (53 +/- 22 s), absolute overshoot/undershoot of PetCO2 (3 +/- 1 mmHg), and settling time (145 +/- 72 s). The resulting CO2 controller dynamics approximate physiological responses, and results from PEEP control were similar to those obtained by manual titration. Multiple dependencies linking the involved variables are discussed. The present controller can help to implement and evaluate objective functions that meet clinical goals.     

神经外科病人术后ICP增高与高碳酸血症的临床相关性研究

目的：探讨NICU术后持续ICP监测病人发生ICP升高的临床意义及其与术后高碳酸血症的相关性。方法：对428例行神经外科开颅手术并安装颅内皮层下颅内压探头的NICU患者,术后给予持续颅内压监测,进行血气分析,判断有无CO2潴留、高碳酸血症。结果：153例患者术后有ICP升高,其中32例患者血气分析结果提示CO2蓄积,占20．91％;改善患者通气情况,及时纠正高碳酸血症可有效降低ICP。结论：术后ICP水平与机体CO2潴留、高碳酸血症的严重程度呈正相关。     

Nonlinear modeling of the dynamic effects of arterial pressure and CO2 variations on cerebral blood flow in healthy humans

The effect of spontaneous beat-to-beat mean arterial blood pressure fluctuations and breath-to-breath end-tidal CO2 fluctuations on beat-to-beat cerebral blood flow velocity variations is studied using the Laguerre-Volterra network methodology for multiple-input nonlinear systems. The observations made from experimental measurements from ten healthy human subjects reveal that, whereas pressure fluctuations explain most of the high-frequency blood flow velocity variations (above 0.04 Hz), end-tidal CO2 fluctuations as well as nonlinear interactions between pressure and CO2 have a considerable effect in the lower frequencies (below 0.04 Hz). They also indicate that cerebral autoregulation is strongly nonlinear and dynamic (frequency-dependent). Nonlinearities are mainly active in the low-frequency range (below 0.04 Hz) and are more prominent in the dynamics of the end-tidal CO2-blood flow velocity relationship. Significant nonstationarities are also revealed by the obtained models, with greater variability evident for the effects of CO2 on blood flow velocity dynamics.     

A new clutter rejection algorithm for Doppler ultrasound

Several strategies, known as clutter or wall Doppler filtering, were proposed to remove the strong echoes produced by stationary or slow moving tissue structures from the Doppler blood flow signal. In this study, the matching pursuit (MP) method is proposed to remove clutter components. The MP method decomposes the Doppler signal into wavelet atoms that are selected in a decreasing energy order. Thus, the high-energy clutter components are extracted first. In the present study, the pulsatile Doppler signal s(n) was simulated by a sum of random-phase sinusoids. Two types of high-amplitude clutter signals were then superimposed on s(n): time-varying low-frequency components, covering systole and early diastole, and short transient clutter signals, distributed within the whole cardiac cycle. The Doppler signals were modeled with the MP method and the most dominant atoms were subtracted from the time-domain signal s(n) until the signal-to-clutter (S/C) ratio reached a maximum. For the low-frequency clutter signal, the improvement in S/C ratio was 19.0 +/- 0.6 dB, and 72.0 +/- 4.5 atoms were required to reach this performance. For the transient clutter signal, ten atoms were required and the maximum improvement in S/C ratio was 5.5 +/- 0.5 dB. The performance of the MP method was also tested on real data recorded over the common carotid artery of a normal subject. Removing 15 atoms significantly improved the appearance of the Doppler sonogram contaminated with low-frequency clutter. Many more atoms (over 200) were required to remove transient clutter components. These results suggest the possibility of using this signal processing approach to implement clutter rejection filters on ultrasound commercial instruments.     

The Interaction of FRC and Ventilation on Occlusion Pressure in Conscious Man

Analytical and experimental results relating the interaction of functional residual capacity (FRC) and ventilation (V) on occlusion pressure in conscious man are presented. An analytical model was developed relating the airway pressure measured 100 ms after occlusion (P100) with FRC and V just before occlusion. By relating the change in diaphragmatic force with time during breathing to that during occlusion, it was found that P100 and IFRC could be linearly related. In order to test this model, 16 normal adult subjects with different FRC values (2.0 to 5.6 1) were studied during periods of increasing ventilation. Subjects increased V by rebreathing a mixture of 7% CO2 and 93% 02. Neither AP100/APC02 nor AV/APCO2 could be correlated to FRC since the differences in motoneuron activity in response to hypercapnia were probably greater than the variations in FRC. Linear regression analysis on all 16 subjects demonstrated a significant effect of FRC on the relationships P100 versus V, and AP100/APCO2 versus A V/APCO2. These experimental findings were in close agreement with analytical predictions and suggest that subjects with larger FRC values have a greater ventilation and ventilatory response for the same occlusion pressure and occlusion pressure response, respectively.     

二氧化碳激光治疗鼻中隔出血的临床研究

目的:探讨二氧化碳激光脉冲式治疗鼻中隔出血的效果和可行性。方法:分别采用二氧化碳激光器的不同激光刀头(输出功率2~3瓦或3~4瓦)脉冲式封闭静脉性和动脉性出血点。结果:58例患者,随访一到六个月,显效40例(69％),有效15例(26%),无效3例(5%)。结论:二氧化碳激光治疗鼻中隔出血疗效确切,治疗方法安全简便、痛苦小、费用低、值得应用推广。     

A dual-mechanism solid-state carbon-monoxide and hydrogen sensor utilizing an ultrathin layer of palladium

Pd-gate MOS sensors were fabricated on p-type silicon wafers. The gate films were 25 and 40 Å thick with an oxide thickness of 100 Å. Contacts were made to allow measurement of the MOS capacitance and of the impedance across the gate film. Voltage shifts in the MOS C-V curves and shifts in the Pd film impedance were measured as functions of 1) the concentration of CO and H2; 2) time as the gas ambient was varied. The devices showed sensitivity to H2at room temperature and to CO and H2at elevated temperatures. When the 25-Å device was exposed to 300 ppm H2in air at room temperature, the C-V curve shifted by -430 mV and the impedance decreased by 20 ω or 5 percent. When the 25-Å device was exposed to 5000 ppm CO in air at 150°C, the C-V curve shifted - 200 mV and the impedance decreased by 140 ω (10 percent). When exposed to 0.1-percent H2in argon, the resistance of the 40-Å device increased by about 2 percent. When measured as a function of time, the changes in MOS capacitance tend to track the changes in impedance. An effect similar to hydrogen-induced drift (HID) was observed for CO at elevated temperature.     

Magnetophonon oscillations in the transverse and longitudinal magnetoresistance of Hg1−xCdxTe

The transverse and longitudinal magnetoresistance (MR) as well as the longitudinal magneto-thermoelectric coefficient of n-type Hg_1-xCd_xTe (MCT) (0.20 < x < 0.33) have been measured at various temperatures (40 ≤ T≤ 140K) as a function of magnetic field (0 ≤ B≤18 kG). Both the transverse and the longitudinal MR clearly exhibit oscillations which are described in terms of magnetophonon (MP) transitions involving the HgTe-like and the CdTe-like longitudinal optical (LO) phonons of MC.T. The field positions of the transverse MR maxima agree with the calculated MP resonances taking into account nonparabolic bands (k • p model for narrow-gap zinc-blende-type semiconductors) and the polaron effect. Those of the longitudinal MR minima are found to coincide with the oscillation minima in the longitudinal magneto-thermoelectric coefficient. However, these minima are shifted by π/2 to lower fields with respect to the positions of the MP resonances. This phase shift was predicted by Barker1314 for the case of strong Landau level damping but has not been previously observed. In contrast, the MP oscillation minima of the longitudinal MR and the oscillation maxima of the transverse MR of n-type InSb (investigated here for comparison) occur exactly at the fields of the MP resonances. Only the oscillation minima of the longitudinal magneto-thermoelectric coefficient are slightly shifted to the side below the MP resonance fields. With regard to the band parameters and the dominant polar optical mode scattering of charge carriers InSb very much resembles MC.T. InSb, however, is a binary compound whereas MC.T is a solid solution. Thus, the phase shift by π/2 to lower fields observed for the oscillation minima in the longitudinal MR and magneto-thermoelectric coefficient of MC.T may be due to alloy scattering. The temperature coefficients of the MP resonance fields of MC.T are found to be substantially smaller than those reported by Takita et al.¹¹ and McClure et al.¹⁰ The larger temperature coefficents are presumably due to unresolved two-phonon structures of the MP oscillations.     

Noninvasive estimation of the aorta input function for measurement of tumor blood flow with

Quantitative measurement of tumor blood flow with [15O]water can be used to evaluate the effects of tumor treatment over time. Since quantitative flow measurements require an input function, we developed the profile fitting method (PFM) to measure the input function from positron emission tomography images of the aorta. First, a [11C]CO scan was acquired and the aorta region was analyzed. The aorta diameter was determined by fitting the image data with a model that includes scanner resolution, the measured venous blood radioactivity concentration, and the spillover of counts from the background. The diameter was used in subsequent fitting of [15O]water dynamic images to estimate the aorta and background radioactivity concentrations. Phantom experiments were performed to test the model. Image quantification biases (up to 15%) were found for small objects, particularly for those in a large elliptical phantom. However, the bias in the PFM concentration estimates was much smaller (2%-6%). A simulation study showed that PFM had less bias and/or variability in flow parameter estimates than an ROI method. PFM was applied to human [11C]CO and [15O]water dynamic studies with left ventricle input functions used as the gold standard. PFM parameter estimates had higher variability than found in the simulation but with minimal bias. These studies suggest that PFM is a promising technique for the noninvasive measurement of the aorta [15O]water input function.     

草酸氧钛酸分解法制备纳米金红石型TiO_2粉体

用硫酸钛与草酸按比例配合 ,析出草酸氧钛酸晶体 ,将其洗涤后在 75 0～ 82 0℃焙烧 ,因草酸氧钛酸分解时 ,其分子中较大部分成分以气体 :CO2 、CO、水蒸气形式挥发到空气中 ,从而固态产物成为纳米级的金红石型二氧化钛粉体。用透射电子显微镜 (TEM)测定 ,其粒径范围为 10～ 35 nm;用 X射线衍射 (XRD)测定 ,其晶型为金红石型。     

Photocatalytic Coupling of CH4 and CO2 to Ethanol on Asymmetric Ce−O−Zn Sites

Partial oxidation of methane (CH₄) to value-added products is significantly challenging due to the highly inert chemical property of CH₄ at ambient conditions and easy over-oxidation into carbon dioxide (CO₂) or carbon monoxide (CO) at elevated temperatures and pressures. Targeting this challenge, the efficient photocatalytic coupling of CO₂ and CH₄ into ethanol is demonstrated, using a cerium (Ce)-doped zinc oxide (ZnO) photocatalyst with abundant Ce─O─Zn units. Under light illumination, CO₂ is adsorbed on the Ce atoms and photo-reduced to CO, and CH₄ is captured by the Zn atoms and photo-oxidized to hydroperoxymethane (CH₃OOH). The close proximity of Ce and Zn atoms on the Ce─O─Zn units allowed to further efficiently couple the as-formed CO and CH₃OOH into ethanol. Without additional Oxygen (O₂) oxidant or sacrificial regent, the ethanol production rate reached 580 µmol g⁻¹ h⁻¹, substantially exceeding previously reports on photocatalytic CH₄ oxidation. This work features to convert two greenhouse gases into value-added chemicals with adjacent and asymmetric reaction sites, suggesting attractive potentials for CH₄ and CO₂ utilization.     

The red shift of ZnSSe metal-semiconductor-metal light emittingdiodes with high injection currents

The reliable n⁺-ZnSSe metal-semiconductor-metal (MSM) blue-green light emitting diodes (LED's) have been fabricated. The contact metal was CuGe/Pt/Au. The current transport mechanisms agree very well with the back to back tunneling diodes. The kink phenomena were observed in the MSM current-voltage curves. In the metal-semiconductor interface, the element Zn in ZnSSe can be replaced by Cu results in some acceptor levels as radiative recombination centers in the MS interface. The peak wavelength in the LED electroluminescent (EL) spectra was strongly dependent on the injection currents from 5 to 40 mA. The peak wavelength and full width at half maximum are 510 and 10 nm, respectively, at 10 mA injection current. When the injection current increases to 15 mA, the peak wavelength shifted to 530 nm due to different recombination centers. Further increasing the injection currents, the peak wavelength shifted slightly to the long wavelength side     

添加玻璃粉对Ba2Ti9O20系瓷料低温烧结的影响

采用H3BO3、ZnO、SiO2、Al2O3、Li2CO3和CaCO3等原料,通过高温熔融、淬火等工艺,获得了低熔点玻璃粉,研究了玻璃粉的熔融、力学性能、介电性能及其含量对MLCC瓷料烧结的影响。结果表明:在Ba2Ti9O20主晶相材料中加入质量分数为4%～7%的低熔点玻璃粉,有利于瓷料在910～950℃低温烧结致密,其绝缘电阻率ρ大于1013Ω·cm,tanδ为(1.2～2.0)×10–4,εr为32～38。     

激光法制备纳米氮化硅及其光谱特性研究

介绍了激光诱导化学气相沉积法制备纳米氮化硅的工艺原理,通过增加正交紫外光束激励NH3分解,提高气相中n(N)/n(Si)比,从而减少产物中游离硅的浓度,制备出粒径7～15 nm的无团聚、理想化学剂量(n(N)/n(Si)=1.314)的非晶纳米氮化硅粉体.采用透射电子显微镜观察粉体形貌,并指出表面效应和量子尺寸效应导致粉体红外吸收光谱和拉曼光谱的"蓝移"和"宽化"现象.采用双光束激励的光诱导化学气相沉积法是制备高纯度纳米氮化硅粉体的理想方法.     

PbO和Bi_2O_3-Li_2CO_3助烧剂对Pb(Zr_(0.9)Ti_(0.1))O_3厚膜热释电性能的影响

采用丝网印刷工艺制备了Pb(Zr0.9T0.1)O3(PZT)厚膜,研究了过量PbO和Bi2O3-Li2CO3共同助烧对PZT厚膜低温烧结特性、微观结构、相构成以及介电和热释电性能的影响。结果表明:随着过量PbO及Bi2O3-Li2CO3添加量的增加,PZT厚膜的烧结温度和晶粒尺寸均逐渐降低。当PbO过量6.4%(质量分数)、Bi2O3-Li2CO3添加量为5.4%(质量分数)时,PZT厚膜可在900℃低温下致密成瓷,且其热释电系数和探测率优值均得到大幅提高;所得样品在30℃时的热释电系数为10.6×10–8C.cm–2.K–1,探测率优值为8.2×10–5Pa–1/2。     

Cs(7DJ)+H2的反应与非反应碰撞转移截面的测定

利用激光泵浦-吸收技术,研究了在样品池中的Cs(7D_J)+H₂→CsH[X¹∑+(v″=0)]+H光化学反应过程。双光子激发Cs-H₂混合蒸气中Cs原子至7²D态,荧光中除有泵浦能级发生的直接荧光外,还包含由精细结构碰撞转移产生的敏化荧光,CsH分子是由7D原子与H₂间的三体碰撞反应产生的。利用780 nm激光测量了CsH X¹∑+(v″=0→v″=21)吸收带。△Ⅰ′和△Ⅰ″分别表示泵浦7D_3/2和7D_5/2时的吸收光强。解速率方程组,得到7D_3/2→7D_5/2和7D_5/2→7D_3/2精细结构转移截面分别为(1.3±0.3)×10^-14和(9.8±2.0)×10^-15cm²。从7D_J碰撞到7D以外态的截面分别为(4.0±1.0)×10^-15(对J=3/2)和(3.6+0.9)×10^-15cm²(对J=5/2)。Cs(7D_J)+H₂→CsH+H的反应截面分别是(1.4±0.5)×10^-16(J=3/2)和(1.1±0.4)×10^-16cm²(J=5/2),7D_3/2与H₂的反应活动...更多性大于7D_5/2。     

Magnetron sputter deposition of A-15 and bcc crystal structure tungsten thin films

The effect of processing parameters on the crystal structure and electrical resistivity of magnetron sputter deposited tungsten thin films was investigated. Formation of body centered cubic (bcc) W was favored when the concentration of impurity oxygen atoms in the films was <5 at.% while the formation of A-15 W was favored between 6 and 10 at.% oxygen. A transition from A-15 W films to bcc W films occurred as the oxygen was removed from the deposition chamber by presputtering the target for extended periods of time. The binding energies of the W atoms in A-15 and bcc W films are similar, as is the binding energy of the O atoms in the two different crystal structures, indicating that the oxygen is not present as a tungsten oxide compound. The resistivity of A-15 W films is always higher than the resistivity of bcc W films due to the increased oxygen concentration and small grain size of the A-15 films. However, the sputter deposition pressure is found to have a greater effect on resistivity. This is attributed to the formation of cracks in the film.     

BaSnO3陶瓷的制备及其电性能研究

以BaCO3、SnO2为原料,微量SiO2、Bi2O3、Sb2O3作烧结助剂,Ta2O5作施主,采用传统的固相反应法,制备出相对密度达97%~99%,平均粒径约为8μm的BaSnO3半导体陶瓷。采用Na2CO3或Li2CO3与Mn(NO3)2的组合作受主掺杂可有效增强BaSnO3陶瓷的晶界效应。当x(Mn(NO3)2)为1%时,BaSnO3陶瓷电阻率达3.3×106Ω.cm,晶粒电阻率为4.3Ω.cm,视在介电常数为1.9×104(1 kHz),经电导激活能测试,估算出晶界势垒约为0.5 eV。