Modulation characteristic of waveguide-type optical frequency combgenerator

We report the modulation characteristics of a waveguide-type optical frequency comb generator (WG-OFCG) with the advantages of compactness, high modulation index and low driving power. The characteristics of the optical frequency comb (OFC) generated when the modulation index exceeds 2π are discussed. The power of the modulation sidebands was measured by the optical heterodyne method with an external-cavity laser as a local oscillator. The dependence of the modulation index of the WG-OFCG on the modulation frequency up to 40 GHz was measured. The generation span of the OFC at the modulation frequency detuned from an integer multiple of the free spectral range (FSR) is discussed     

Drain structure optimization for highly reliable deep submicrometern-channel MOSFET

A guideline for n^- fully gate overlapped (FOLD) structure design optimization has been studied. From the viewpoint of reliability, the greatest reduction in substrate current directly leads to the most reliable n^- design for the FOLD structure. The current path modulation phenomenon due to the trapped charge at the n ^- extension region dominates the hot-carrier induced characteristics change for conventional lightly doped drain (LDD) structure with side-wall spacer. This phenomenon is minimized in the FOLD structure due to its higher controllability of the gate electrode than the LDD structure at the n^- extension region. Furthermore, it was also confirmed that the 0.3 μm optimized FOLD structure can achieve high circuit performance at 3.3 V operation, maintaining hot-carrier resistance     

Impact of compression,physical aging,and freezing rate on the crystallization characteristics of an amorphous sugar matrix

Amorphous matrices made up of sugar molecules, are frequently used in food and pharmaceutical industries. A drawback to their use is that they are susceptible to collapse, as a result of water uptake and an increase in temperature and subsequently crystallize. Herein, the crystallization characteristics of amorphous sugar (sucrose and α-lactose) preparations were analyzed, with the purpose of obtaining knowledge that could lead to the prediction of how long the amorphous state is retained under various conditions. The impact of compression, physical aging and freezing rate on the induction period (t_ind) for crystallization were examined. Freeze-dried sugar samples were compressed at 74 or 443 MPa (5 min) and then rehumidified at specified RHs. Some freeze-dried sucrose samples were physically aged, and alternatively freeze-drying was conducted under different conditions. The isothermal crystallization of the prepared samples at different temperatures (T), the glass transition and the crystallization temperature (T_cry) were measured, using differential scanning calorimetry. The compression markedly decreased the t_ind, while significantly lowered the hygroscopicity. Physical aging and slower-freezing also shortened the t_ind. The t_ind was found to be correlated exclusively with (T_cry–T), regardless of rehumidification, compression, sugar type, physical aging and freezing rate in the freeze-drying process.     

Molecular cloning and expression of inducible nitric oxide synthase in chick embryonic ventricular myocytes

In order to determine the effect of kappa-opioid receptor agonist on the beta1-adrenoceptor stimulation in the heart, the effects of norepinephrine (NE), a beta1-adrenoceptor agonist, on contraction and electrically induced intracellular calcium ([Ca2+]i) transient in the single rat ventricular myocyte pretreated with a kappa-opioid receptor agonist, trans-(+/-)-3, 4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)-benzeneacetamide (U50,488H), at 0.01-1 microM were studied with a video edge tracker method and a spectrofluorometric method using fura-2 as calcium indicator, respectively. NE at 0.01-10 microM augmented both twitch amplitude and electrically induced [Ca2+]i transient dose-dependently, which were abolished by propranolol at 1 microM, a beta-adrenoceptor antagonist. The effects of NE on both contraction and [Ca2+]i transient were attenuated in a dose-dependent manner by U50,488H at 0.01-1 microM, which itself had no effect at all. The maximum response ( Emax) was decreased, while the concentration that produces 50% of the maximum response (EC50) was enhanced, by U50, 488H. The inhibitory effects of U50,488H on beta-adrenoceptor stimulation were completely blocked by pretreatment with norbinaltorphimine, a specific kappa-opioid receptor antagonist at 1 microM, or preincubation with pertussis toxin (PTX) at 200 ng/ml for 6 h. On the other hand, the inhibition on NE-induced augmentation in electrically induced [Ca2+]i transient by U50,488H was not affected by pretreatment with U73122, a specific inhibitor of phospholipase C (PLC), at 10 microM for 30 min. U50,488H attenuated the augmentation of the electrically stimulated [Ca2+]i transient induced by forskolin at 0.1 and 0.5 microM. It did not, however, affect the augmentation of the electrically induced [Ca2+]i transient by N6, 2'-O-dibutyryl adenosine cyclic monophosphate (DB-cAMP). The results suggest that kappa-opioid receptor stimulation by U50,488H at 10(-6 )M or lower may inhibit the effects of beta-adrenoceptor stimulation by acting at a PTX-sensitive G-protein and AC, but not via the phosphoinositol pathway.     

Selectivity of felodipine for depolarized ventricular myocytes: a study at the single-cell level

We studied the effects of felodipine (a second-generation dihydropyridine Ca2+ channel blocker) on excitation-contraction coupling (E-C coupling) in single isolated guinea-pig ventricular myocytes, using the whole-cell perforated patch-clamp technique or the Ca indicator, indo-1. Felodipine inhibited both L-type Ca2+ channel currents (ICa) and cell contractions in a concentration-dependent manner (10 pM to 100 nM) when we used a holding potential of -80 mV or -40 mV. The potency of felodipine was sharply dependent on a holding potential. Namely, use of a more depolarized holding potential markedly increased the potency of felodipine for inhibition of ICa and cell contraction. Next we current-clamped cells and obtained the resting membrane potential of -82 +/- 8 mV. When cells were current-injected at 0.1 Hz, exposure to 10 nM felodipine slightly but significantly diminished the amplitude of cell contractions (7.2 +/- 1.6 to 6.7 +/- 1.7 microns, P < 0.05) within 10 min. When cells were field stimulated, exposure of cells to 10 nM felodipine also slightly diminished the amplitude of cell shortening (5.1 +/- 2.0 to 4.6 +/- 1.9 microns, P < 0.05) and [Ca2+]i transients. We observed clear voltage-dependent blockade of E-C coupling by felodipine in ventricular myocytes. Thus, therapeutic concentrations (1-10 nM) of felodipine could inhibit E-C coupling in depolarized ventricular myocytes, which might simulate an ischemic or failing heart.     

Brain pH responses to acetazolamide and hypercapnia in cats

The involvement of increased brain tissue CO2 tension in acetazolamide-induced brain acidosis was investigated by comparing the brain pH response to acetazolamide with that to hypercapnia. CO2 and pH sensors were placed bilaterally into cerebral white matter to 15 mm depth in cats. Group 1 cats (n = 9) breathed spontaneously, and in situ brain tissue PCO2, and pH (PbCO2 and pHb) were measured after intravenous acetazolamide administration (20 mg/kg). Group 2 cats (n = 9) were paralyzed and ventilated mechanically, and the changes of pHb were investigated by adjusting the ventilation to maintain the same Pbco2 values as in the acetazolamide-treated group. PbCO2 changes were not significantly different between the two groups. However, pHb responses were quite different: the fall in pHb was progressive in Group 1 but transient in Group 2. Brain acidosis after acetazolamide administration is not due to the rise in brain tissue CO2 tension.