Search

We have investigated broadband coherent anti-Stokes Raman scattering (CARS) microspectroscopy using the soliton pulses from a photonic crystal fiber. CARS spectrum shows a dispersive shape due to the contributions from a frequency-independent nonresonant component and from a resonant component that corresponds to spontaneous Raman scattering. To extract the resonant component from the CARS spectrum, the functional form of this component was commonly assumed to be a simple Lorentzian function and a nonlinear fitting procedure was used previously. In this study, we derived a CARS spectral function that takes into account the finite spectral width of a pump pulse and the CARS spectrum of diamond powders was fitted using the derived spectral function. It was found that the linewidth obtained using this function agreed with the linewidth of spontaneous Raman scattering much better than the linewidth obtained using a CARS spectral function commonly used previously.

Ultrabroadband optical pulses generated through self-phase and induced-phase modulation effects and ultrashort optical pulses whose phases were compensated for using a 4f pulse shaper with a spatial phase modulator were generated. Interferometric autocorrelation, frequency-resolved optical gating and spectral phase interferometry for direct electric-field reconstruction (SPIDER) measurements were made to characterize these pulses, and the results were compared. The generation of 5.0 fs (2.4 cycle) or shorter optical pulses was confirmed. For much shorter pulses, below-two-cycle or monocycle optical pulses, single-shot characterization excluding the errors due to the pulse-to-pulse fluctuation is essential. The sensitivity of SPIDER, which is the most advantageous characterization technique apart from its low sensitivity, was improved by a factor of about a hundred (~1 nJ/THz-bandwidth). Instead of a chirped reference pulse split from the pulse to be characterized, a powerful external pulse from a Ti:sapphire laser amplifier as a highly intensive chirped pulse was employed. By use of this modified SPIDER, the characterization of an over-one-octave ultrabroadband optical pulse was performed. This modified-SPIDER method is the most promising for characterization of monocycle optical pulses.

We experimentally demonstrate the generation of 5.0-fs optical pulses (2.5 µJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation. Pulse compression of the broadband pulse (500–1000 nm) from an argon-filled capillary fiber is achieved with a liquid-crystal spatial light modulator without any prechirp compensation. The output pulse width is found to be 4.1 fs by a fringe-resolved autocorrelator fitted with a transform-limited pulse and to be 5.0 fs by second-harmonic generation frequency-resolved optical gating with marginal correction. It is to our knowledge the shortest pulse ever generated by use of only a spatial light modulator for phase compensation.

We experimentally observed the periodic oscillatory structure in the second-harmonic spectrum when we simultaneously propagated intense fundamental and second-harmonic pulses from a Ti:sapphire laser-amplifier system in an argon-filled capillary fiber. The periodic oscillatory structure in the second-harmonic spectrum is only due to the induced-phase modulation (IPM) which, in general, is hidden because of strong self-phase modulation. It is found that this structure can be well explained by the interference of the electric field components in the second-harmonic pulse. These electric field components are generated based on IPM by the fundamental pulse. The theoretical analysis of the nonlinear pulse propagation agrees well with experimental results. In addition, the measured dependence of the modulated spectral behavior on the delay time, including the spectral feature, the oscillatory period and the range of the delay time between two pulses, indicates the excellent agreement with the numerical analysis which includes the medium and waveguide dispersion and the steepening effect.

Wave-propagation equations, including effectively the second derivative in time under the condition of a small difference between the group and phase velocities and the first derivative in position /spl xi/ in the group velocity coordinate, are derived based on the slowly evolving wave approximation. These can describe ultrabroadband optical pulse propagation with not only self-phase modulation (SPM), but also induced-phase modulation (IPM) in the monocycle regime in a fiber. It is shown that linear dispersion effects can be rigorously included in the numerical calculations. Calculations including SPM in a single-mode fused-silica fiber with the Raman effect are performed and compared with experimental results. Also, calculations including IPM in the fused-silica fiber are compared with experimental results. The effects of each term in the calculations on spectra are analyzed and it is shown that inclusion of the Raman effect and the dispersion of the effective core area is important for obtaining better agreement with experiments. It is shown that inclusion of more than third-order dispersion terms is necessary for calculations of monocycle pulse propagation.

An ultra-broad spectrum over the range from 480 to 900 nm is experimentally generated by induced-phase modulation (IPM) of two 120 fs intense optical pulses copropagating in a 3-mm single-mode fused-silica fiber for the first time to our knowledge. The center wavelengths of the two pulses are 640 nm and 795 nm, respectively. The Fourier transform of this spectrum yields a transform limited 4 fs optical pulse. This IPM-induced spectrum broadening method opens the way to monocycle optical pulse generation in the near future.

We have experimentally generated an ultrabroadband pulse from 380 to 1000 nm in a photonic crystal fiber by induced phase modulation by use of a fundamental pulse and its second-harmonic pulse from a Ti:sapphire oscillator.

We propose a novel Bluetooth network architecture, called multihop Bluetooth network (MBNET). In the MBNET, one of the nodes is the base station. Each node is assumed to have two Bluetooth devices. The fundamental difference of MBNET from a conventional Bluetooth network architecture, called scatternet, is that no Bluetooth device belongs to multiple piconets. Thus, there is no piconet-switch overhead. The basic design principle of the MBNET topology is that each node should have at least two disjointed paths to the base station. We argue the topology optimization of the MBNET, from perspectives such as performance and reliability, and present several topology design guidelines using simple examples. In MBNET, the base station is in charge of designing MBNET topology and needs to obtain the entire node information. We briefly describe a node information management method, which is composed of hierarchical neighbor discovery protocol, neighbor information reporting protocol, and in-service neighbor discovery protocol. We present an algorithm to construct the topology of MBNET and evaluate its performance. It is shown that the proposed algorithm has a satisfactory performance in providing every node two disjointed paths to the base station.

Generation of an ultrabroadband optical pulse with a fluent frequency-dependency of the phase is important, for example, for shaping multi-wavelength optical pulses and monocyclization. When two optical pulses, one fundamental, the other generated by second harmonic generation, are co-propagated in a nonlinear waveguide, induced-phase modulation (IPM) between them, as well as self-phase modulation (SPM), can be used to broaden the spectrum of each pulse. Since the second-harmonic wave as well as the fundamental wave are generated from one common femtosecond pulse, the carrier-phase difference between their waves is constant and these can be synthesized constructively after propagation. For a case where a capillary fiber filled with noble gas is used as an almost-dispersionless, nonlinear waveguide, we analysed the optimum delay between two pulses and powers required for covering spectrum between two pulses and it was predicted that the generation of the optical pulses whose spectrum covers from near-ultraviolet to near-infrared was possible. To verify these predictions, experimental studies have been performed.

Summary form only given. Generation of an ultra-broadband optical pulse with a fluent frequency-dependency of the phase is important, for example, for shaping multi-wavelength optical pulses and monocyclization. When two optical pulses, one fundamental, the other generated by second harmonic generation, are co-propagated in a nonlinear waveguide, induced-phase modulation between them, as well as self-phase modulation, can be used to broaden the spectrum of each pulse. Since the second-harmonic wave as well as the fundamental wave are generated from one common femtosecond pulse, the carrier-phase difference between their waves is constant and these can be synthesized constructively after propagation. In this research, we analyzed the case where a capillary fiber filled with noble gas is used as an almost-dispersionless, nonlinear waveguide. Since the optical field is not completely confined in the glass capillary during propagation, the loss always occurs in this method. We consider a case where two optical pulses with different center frequencies and widths are co-propagating in a capillary fiber. The analytic equations for nonlinear chirps with loss, but without dispersion are obtained for two Gaussian input-pulses using slowly varying envelope approximations.

The amplitude and phase of 5.0-fs optical pulses were characterized by a spectral phase interferometry for direct electric-field reconstruction (SPIDER) technique. This is the shortest pulse ever measured by the SPIDER technique to our knowledge.

We compared several server algorithms and found that performance of server selection can be improved using QoS statistics (average of past weeks QoS values) and real time QoS probing. Specifically, a set of candidate servers are selected based on QoS statistics for a given time section of the day and day of the week. A target server is, then, selected among the pre-selected candidate servers based on real time QoS measurement using echoping.

Monoamine oxidase type A and type B are major neurotransmitter-degrading enzymes in the CNS. The type A is present on mitochondrial outer membranes in the whole extent of noradrenergic and dopaminergic neurons, including their axon terminals. The type B is present in serotonergic neurons, but its subcellular localization has not been elucidated. In the present study, we used both a double-labeling immunofluorescence method and electron microscopic immunohistochemistry to examine the subcellular localization of monoamine oxidase type B in serotonergic neurons projecting from the dorsal raphe nucleus to the suprachiasmatic nucleus in the rat brain. In the dorsal raphe nucleus, serotonin-positive neuronal cell bodies were clustered, and virtually all of these cell bodies were also positive for monoamine oxidase type B. By contrast, serotonin-negative neuronal cell bodies were mostly free of this enzyme. Within the neuronal cell bodies and dendrites that were positive for monoamine oxidase type B, most mitochondria contained this enzyme on their outer membranes, but a substantial proportion of mitochondria lacked this enzyme. In the suprachiasmatic nucleus, serotonin-positive varicosities were concentrated, but none of these varicosities exhibited monoamine oxidase type B. In this nucleus, mitochondria were found in almost all serotonin-positive axon terminals, but monoamine oxidase type B was not observed in any axon terminal that contained mitochondria. Our results show that there are two kinds of mitochondria in serotonergic neuronal cell bodies and dendrites: one containing monoamine oxidase type B on their outer membranes, and the other lacking this enzyme. In addition, mitochondria in serotonergic axon terminals do not possess monoamine oxidase type B. It is suggested in serotonergic neurons that only mitochondria lacking monoamine oxidase type B are transported by axonal flow up to axon terminals. It is also probable that mitochondria containing monoamine oxidase type B are transported along the axons, but that this enzyme undergoes a change, for example, conformational change, decomposition or removal from the membranes.

92-fs, 75-MHz-repetitive pulses from a simple laser-oscillator glass-fiber system were compressed to 7.1-fs transform-limitedly by a chirp compensator consisting of a prism-pair and a spatial-phase-modulating pulse shaper that in-situ-adjusts independently and accurately any order dispersions.

Summary form only given.To describe the propagation of short-duration and broadband optical pulses in a fiber, the conventional slowly-varying envelope approximation (SVEA), has the following two limitations: (1) the approximation of the slowness of the envelope compared with the optical cycle time becomes invalid for an ultrashort pulse, (2) its treatment of linear dispersion of the fiber, i.e., including ordinary up to 3rd-order terms around the center frequency of the pulse, becomes incorrect when the bandwidth of the pulse spectrum becomes extremely large. To solve the first problem, we have derived a nonlinear fiber propagation equation by the method similar to the slowly-evolving-wave approximation. To solve the second problem, we have developed a novel method to include all orders of terms for the linear material and waveguide dispersion in the numerical calculations. In summary, a nonlinear pulse propagation equation that can be used to describe ultrabroadband and small-cycle optical pulses in a fiber is derived and the calculated spectra obtained from it for self phase modulation agrees well with the experimental spectra.

The Nippon Medical School Foundation was an institution that developed after the closing of the Saiseigakusha Medical School, inheriting the spirit of the latter. During the period extending from 1912 to May 1916, the Ministry of education remained reluctant to approve of the Foundation as a Ministry-designated institution. Actively lobbying the Ministry were people such as Tatsukichi Irisawa, a member of the "Meiji Society of Medicine", a partisan clique of the University of Tokyo Medical School. Meanwhile within the Foundation itself, an internal strife took place between the Directors Kenzo Isobe and Taketaro Takizawa, which brought about its disintegration and collapse from within. Some four hundred and fifty students lodged their petition for official approval, sealed with blood, to the School authorities and to the Ministry. Having their petition for approval rejected, all these four hundred and fifty odd students withdrew from the School and founded within the building of the Tokyo Physics School a 'Tokyo Medical Training School'. Some forty students who did not withdraw, in collaboration with members of the teaching staff, re-established the Nippon Medical School Foundation.

The transient appearance of GTP cyclohydrolase I (GCH)-immunoreactive (ir) cells in the ventral lateral geniculate nuclear region of mice was detected by use of an avidin-biotin peroxidase complex method with an antibody specific for an oligopeptide of rat GCH (residues from 12 to 23, GFPERELPRPGA). In this brain region, we found for the first time novel GCH-ir cells already at postnatal day 1 (P1). The numbers reached maximum at P14 and decreased until P29, and they had mostly disappeared by P56. These cells were tyrosine hydroxylase negative and aromatic L-amino acid decarboxylase negative, indicating a lack of dopamine or serotonin production, and thus do not belong to the monoaminergic neuron system.

The private Saiseigakusha medical school was suddenly ordered closed on August 30, 1903, under pressure from the Ministry of Education and the Tokyo University Akamon faction (Meiiji Ikai). The more than 700 remaining medical students at Saiseigakusha were astonished and despondent to see the road to learning closed to them. However, Shigenori Sonoda, leader of the medical students, and four others sent out a manifesto to the more than 700 former Saiseigakusha students, calling them to assemble at the Hongo Central Hall. There they formed the Doso Igaku Koshukai ("Classmates' Medical Institute"), and resolved to continue their studies. Former Saiseigakusha lecturer Kiyotada Ishikawa and three others helped with this institute ("Tokyo Medical school"), and moved to 59 Sendagi-machi, Hongo. In April of 1910, the Tokyo Igakkou merged with the private Nippon Igakkou ("Japan Medical School"), to become the present Nippon Ika Daigaku ("Nippon Medical College").

We experimentally demonstrate the generation of intense ultrabroadband optical pulses whose spectrum ranges from 300 to 1000 nm (700-THz bandwidth) with a well-behaved spectral phase and 23-muJ pulse energy by a novel, simple setup utilizing induced phase modulation (IPM) in an argon-filled single-mode hollow waveguide. Fundamental as well as second-harmonic pulses produced by one common femtosecond pulse from a Ti:sapphire laser-amplifier system are copropagated in the hollow waveguide. The effect of the delay time between the two input pulses on the IPM spectral broadening is clarified and confirmed to agree with the theoretical result. It is found that the compressed pulse duration from this pulse is 1.51 fs if its phase is completely compensated for.

With an immunofluorescent technique, catecholaminergic neurons were identified for the first time in the dorsal and medial thalamus and in the ventralis telencephali (the rostro-medial part of the lobus olfactorius) of the goldfish brain. Serotonin-containing neurons were found in the pretectal area.

The subcellular localizations of tryrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) in the adrenal glands of the frog and rat have been examined by a peroxidase-antiperoxidase (PAP) method. TH was localized in the ground substance of the adrenaline-containing cells and noradrenaline-containing cells, but not in the nucleus or in the mitochondria. TH was also located on the outside of the membrane of the chromaffin granules. DBH was observed only inside the granules. PNMT was found not only in the ground substance but also on the membrane of some adrenaline-containing granules. Cortical lipid cells of the frog adrenals did not show TH-, DBH-, and PNMT-reactions. The negative reactions to TH-, DBH-, and PNMT-antiserum exhibited by the summer cells of the frog adrenals prove that they belong to the cortical cells.

The localization of catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT)], of serotonin (5-HT), and adrenocorticotropin (ACTH) in the pituitary of bullfrog (Rana catesbeiana), rat, hamster, and dog was examined by the immunofluorescence method. Many TH- and DBH-positive but PNMT-negative noradrenalin cells and 5-HT-positive serotonin cells were first observed in the pars distalis of the frog pituitary together with small numbers of ACTH-positive cells, in marked contrast to our previous findings that TH-positive but DBH-negative dopamine cells are rare in the anterior lobe of rat and dog pituitary. The entire population of cells of the pars intermedia showed a weak ACTH-like immunoreaction. Although most of these cells were TH- or 5-HT-negative, TH-positive but DBH-negative dopaminergic varicose fibers surrounded these cells. Among cells of the pars intermedia of the frog, 5-HT-positive cells with processes were also scattered. In the neural lobe, TH- and 5-HT-immunoreactive fibers were rarely seen.

Using the peroxidase-antiperoxidase immunohistochemical technique, carnosine-like immunoreactivity was demonstrated to localize specifically within the primary olfactory neuron.

Summary form only given. A tapered-silica fiber has recently been used in producing an ultra-broad band spectrum. By heating and stretching a 10 mm silica fiber with a 125 /spl mu/m outer diameter and a 9 /spl mu/m core diameter, a 70 mm totally long tapered fiber was produced with a 25 mm long waist of 2 /spl mu/m uniform diameter. A typical resultant ultra-broad band spectrum was found to range from 425 to 955 nm. By using our second-harmonic frequency-resolved optical gating (SH-FROG) apparatus, the intensity and phase profiles of the output pulse from the fiber in both temporal and frequency domains were determined. The output pulse was centered at 785 nm and had an averaged power of 26 mW for the input with a 150 fs duration. We performed pulse compression with a liquid crystal spatial light modulator (SLM) on the basis of the spectrum phase information obtained by the SH-FROG measurement. This was the first pulse compression of an output pulse from a tapered fiber using an SLM. That is, chirp compensation of the complicated frequency-dependent phase in comparison with that of the conventional silica-fiber output was carried out successfully by the spatial light modulation technique for the first time.

Summary form only given. In this paper, we demonstrate the experimental evolution of ultra-broad spectra generated by photonic crystal fibers (PCFs) of different lengths, and theoretically analyze the nonlinear process based on our derived nonlinear propagation equation beyond the slowly-varying-envelope approximation (SVEA). The calculated results of the complicated frequency-dependent phase are significantly useful for extremely flexible and accurate active-chirp compensation by a 4-f pulse shaper with a spatial phase modulator for monocycle-pulse generation.

Summary form only given. Optical pulses in the 5-fs region have been generated using chirped mirrors for chirp compensation. Chirped mirrors have the advantage of high throughput. However, the difficulty of obtaining a very large bandwidth, the inter-dependence of different phase orders, and the inability to fine-tune the phase in the experimental set-up are disadvantages. On the other hand, the pulse shaping technique (Weiner et al, IEEE J. Quantum Electron. vol. 28, p. 909, 1992) using a liquid crystal spatial light modulator (SLM) for pulse compression has the advantages of large bandwidth (300-1500 nm) and in-situ adaptive phase control. Recently it was used to compress broadband pulses with pre-chirp compensation by the prism pair to obtain sub 6-fs pulses (Xu et al, 2000). Here, we demonstrate experimentally that the pulse shaper with the SLM can be used to compress broadband (500-1000 nm) pulses from the argon-filled capillary fiber without any pre-chirp compensation to generate 5.0-fs pulses. By not using any pre-chirp compensation optics, the optical throughput increases, the alignment becomes easier and the total spectral width is not cut. Also, the important parameter of the phase pattern applied by the SLM for generating pulses close to the transform-limit is identified. To accurately evaluate the pulses thus generated, second-harmonic frequency-resolved optical gating (SH-FROG) is used.

A thin single crystal of 2‐methyl‐4‐nitroaniline for second harmonic generation experiment is prepared by vapor phase growth. The crystal is used as a high‐index top layer on a tapered slab‐type waveguide. A Nd:yttrium aluminum garnet laser (1.064 μm) is guided as a fundamental wave. The phase match condition between the fundamental wave (the TE first wave) and the second harmonic wave (the TE second wave) is realized by coincidence of both propagation constants with translational adjustment of the thickness of the waveguide.