A high-speed and highly uniform submicrometer-gate BPLDD GaAsMESFET for GaAs LSIs

The authors present formation conditions for ion-implanted regions of a GaAs buried p-layer lightly doped drain (BPLDD) MESFET that can improve short-channel effect, V_th uniformity, and FET operating speed, simultaneously. For 0.7-μm gates, a Mg⁺ dose of 2×10¹² cm^-2 at 300 keV and a Si⁺ dose of 2×10¹² cm^-2 at 50 keV are suitable for the p layer and n' layer, respectively. A σV _th of 7 mV is realized. Gate-edge capacitance of the 0.7-μm-gate BPLDD that consists of both overlap capacitance and fringing capacitance is successfully reduced to 0.5 fF/μm, which is about 50% of that of a non-LDD buried p-layer (BP) FET. Another parasitic capacitance due to the p-layer was found to have less effect on the speed than the gate-edge one. Consequently, the gate propagation delay time of the BPLDD can be reduced to 15 ps at power dissipation of 1 mW/gate, which is about 65% of that of a BP. Applying the 0.7-μm-gate BPLDD to 16-kb SRAMs, the authors have obtained a maximum access time of less than 5 ns with a galloping test pattern     

Chest flow during the initial inspiratory phase (V0.1) in pulmonary diseased patients

We measured the chest flow 0.1 s after the onset of the inspiratory phase (V0.1) in patients with chronic pulmonary emphysema (CPE: n = 5), interstitial pneumonitis (IP: n = 5) and normal subjects (Nor: n = 5). The subjects sat in a body box and breathed air from outside of the body box. V0.1 was measured during rest and during maximal breathing (V0.1-rest, V0.1-max) and then these results were compared with P0.1 (P0.1 rest, P0.1-max) values. V0.1-rest was not significantly different between the three groups (Nor: 0.25 +/- 0.10, CPE: 0.27 +/- 0.06, IP: 0.26 +/- 0.06, l/s), whereas the P0.1-rest in IP patients was significantly greater than in normal subjects (Nor: 1.98 +/- 0.61, CPE: 3.00 +/- 0.80, IP: 3.60 +/- 0.68 hPa; P < 0.05 compared with normal). The V0.1-max in CPE and IP patients was significantly lower than in normal subjects (Nor: 3.66 +/- 1.16, CPE: 0.82 +/- 0.25, IP: 1.02 +/- 0.21 l/s, P < 0.05 compared with normal subjects (Nor: 3.66 +/- 1.16, CPE: 0.82 +/- 0.25, IP: 1.02 +/- 0.21 l/s, P < 0.05 compared with normal), whereas P0.1-max in IP patients was not significantly different with in normal subjects (Nor: 33.2 +/- 10.2, CPE: 9.8 +/- 3.7, IP: 19.5 +/- 3.4 hPa, P < 0.05 compared with normal, P < 0.05 compared with CPE). A simulation of the influence of the mechanical properties of the respiratory system on V0.1 and P0.1 using the Runge-Kutta method suggested that V0.1 was negatively affected by airway resistance but positively affected by chest wall and lung compliance. In contrast, the influence of respiratory mechanics on P0.1 was much less than on the V0.1, except for highly decreased lung compliance. In CPE patients, it was suspected that mechanical disorders might not simply be the determining factors of V0.1-max, but that limitations of the neuro-muscular drive due to chest wall deformity may also play a definitive role in the smaller V0.1-max. In contrast, it may be inferred that IP patients had to exert greater inspiratory effort as compared with the other two groups in order to maintain a similar V0.1-rest because of the increased airway resistance and decreased tissue compliance; thus these abnormal mechanical properties suppress the increase in the V0.1-max. It may be concluded that V0.1 is a good index of chest wall acceleration, which is determined by both the neuro-muscular drive and the mechanics of the respiratory system.     

Mild hypothermia after cardiac arrest in dogs does not affect postarrest cerebral oxygen uptake/delivery mismatching

PURPOSE: To compare measurements of cerebral arteriovenous oxygen content differences (oxygen extraction ratios, oxygen utilization coefficients) in dogs after cardiac arrest, resuscitated under normothermia vs. mild hypothermia for 1-2 h or 12 h. METHODS: In 20 dogs, we used our model of ventricular fibrillation (no blood flow) of 12.5 min, reperfusion with brief cardiopulmonary bypass, and controlled ventilation, normotension, normoxemia, and mild hypocapnia to 24 h. We compared a normothermic control Group I (37.5 degrees C) (n = 8); with brief mild hypothermia in Group II (core and tympanic membrane temperature about 34 degrees C during the first hour after arrest) (n = 6); and with prolonged mild hypothermia in Group III (34 degrees C during the first 12 h after arrest) (n = 6). RESULTS: In Group I, the cerebral arteriovenous O2 content difference was 5.6 +/- 1.6 ml/dl before arrest; was low during reperfusion (transient hyperemia) and increased (worsened) significantly to 8.8 +/- 2.8 ml/dl at 1 h, remained increased until 18 h, and returned to baseline levels at 24 h after reperfusion. These values were not significantly different in hypothermic Groups II and III. The cerebral venous (saggital sinus) PO2 (PssO2) was about 40 mmHg (range 29-53) in all three groups before arrest and decreased significantly below baseline values, between 1 h and 18 h after arrest; the lowest mean values were 19 +/- 19 mmHg in Group I, 15 +/- 8 in Group II (NS), and 21 +/- 3 in Group III (NS). Postarrest PssO2 values of < or = 20 mmHg were found in 6/8 dogs in Group I, 5/6 in Group II and 4/6 in Group III. Among the 120 values of PssO2 measured between 1 h and 18 h after arrest, 32 were below the critical value of 20 mmHg. CONCLUSIONS: After prolonged cardiac arrest, critically low cerebral venous O2 values suggest inadequate cerebral O2 delivery. Brief or prolonged mild hypothermia after arrest does not mitigate the postarrest cerebral O2 uptake/delivery mismatching.     

Threshold current density in solution-grown GaAs laser diodes

Threshold current density of solution-grown GaAs laser diodes with a Fabry-Perot cavity were measured at 77 and 300°K by varying the acceptor concentration in thepregion Na. Threshold current density was lower in the series of diodes with larger values of Nathan in the series of diodes with smaller values of Nafor the diode length between 0.1 and 1 mm. Through these experiments diodes with the threshold current density as low as3 times10^{2}A/cm²at 77°K and2.8 times 10^{4}A/cm²at 300°K for the diode length of 1 mm, and as low as 10³A/cm²at 77°K and4.5 times 10^{4}A/cm²at 300°K for the diode length of 0.1 mm were obtained.     

Coupling coefficient modulation of waveguide grating using sampledgrating

A new method of modulating the coupling coefficient along the waveguide is proposed. The effect of our method, which uses a nonperiodic sampled grating, is demonstrated both theoretically and experimentally. A Bragg filter is fabricated on an InGaAsP/InP wafer utilizing the method, and the sidelobe level is shown to improve by 7 dB compared with a conventional filter with a uniform coupling coefficient. The experimental results are found to be in good agreement with calculations     

Super-early iodine-123-iodoamphetamine SPECT imaging of human primary motor cortex

This study was designed to visualize the motor function area related to finger movements in normal human brain using super-early (first 640 sec of acquisition) [123l]iodoamphetamine ([123I]IMP) SPECT. METHODS: Seven healthy male volunteers performed paired, isolated baseline and task sessions. The task was a right thumb-to-fingers opposition task, which was loaded for the initial 11 min of the session. A high-performance, four-head SPECT camera was used. At each session, administration of 222 MBq [123I]IMP was followed by 16 serial 160-sec dynamic SPECT acquisitions. To obtain matched brain anatomical images, MRI was also performed using the same slice formation as in the SPECT study. After image reconstruction, ROIs were set on bilateral sensorimotor hand areas (SMHA), the supplementary motor area (SMA), the frontal, temporal and occipital lobes and the cerebellar hemispheres. The percent increase of ROI activity (%INC) in the task session compared with that in the baseline session was calculated in each ROI after normalization to the global brain radioactivity. RESULTS: There was significant activation of the left SMHA by the task, the amplitude of which was maximal in the initial phase of dynamic images (the super-early phase). This area was located in the left peri-central area identified on the analogous slice in the MR image. The left SMHA showed gradual and statistically significant decrease of %INC during the three phases. CONCLUSION: Super-early [123I]IMP may be used to identify the primary motor cortex and to evaluate its function in some pathological conditions.     

高产人参皂甙β—葡萄糖苷酶菌种的筛选

选取８种菌,筛选了能水解人参皂甙β－葡萄糖苷键的β－葡萄糖苷酶的高产菌株,研究了酶法改变人参皂甙糖基、以去掉人参皂甙Ｒｇ３上的一个葡萄糖基变成高抗癌Ｒｈ２皂甙的可能性,结果,８种菌所产的酶,均有纤维素外切酶的对硝基七酚基－β－葡萄糖苷（ｐＮＰＧ）酶活力,但其中２种菌所产的酶不具有水解人参皂甙－β－葡萄糖键的酶活,只有３种菌所产的酶水解人参皂甙－β－葡萄糖键的酶活高,证明了纤维素外切酶和人参皂甙－β