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J Kono

Publications and source records attributed to J Kono.

At least 19 recordsLinked to original sources
PubMed2006

Cooperative recombination of a quantized high-density electron-hole plasma in semiconductor quantum wells.

We investigate photoluminescence from a high-density electron-hole plasma in semiconductor quantum wells created via intense femtosecond excitation in a strong perpendicular magnetic field, a fully quantized and tunable system. At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. In addition, changes in the linewidth, carrier density, and magnetic field scaling of the photoluminescence spectral features correlate precisely with the onset of random directionality, indicative of cooperative recombination from a high-density population of free carriers in a semiconductor environment.

Journal Article↗
PubMed2006

Excitons in carbon nanotubes with broken time-reversal symmetry.

Near-infrared magneto-optical spectroscopy of single-walled carbon nanotubes reveals two absorption peaks with an equal strength at high magnetic fields (>55 T). We show that the peak separation is determined by the Aharonov-Bohm phase due to the tube-threading magnetic flux, which breaks the time-reversal symmetry and lifts the valley degeneracy. This field-induced symmetry breaking thus overcomes the Coulomb-induced intervalley mixing which is predicted to make the lowest exciton state optically inactive (or dark).

Journal Article↗
PubMed2005

Ultrafast quenching of ferromagnetism in InMnAs induced by intense laser irradiation.

Time-resolved magneto-optical Kerr spectroscopy of ferromagnetic InMnAs reveals two distinct demagnetization processes--fast (<1 ps) and slow (approximately 100 ps). Both components diminish with increasing temperature and are absent above the Curie temperature. The fast component rapidly grows with pump power and saturates at high fluences (>10 mJ/cm(2)); the saturation value indicates a complete quenching of ferromagnetism on a subpicosecond time scale. We attribute this fast dynamics to spin heating through p-d exchange interaction between photocarriers and Mn ions, while the approximately 100 ps component is interpreted as spin-lattice relaxation.

Journal Article↗
PubMed2005

Stability of high-density one-dimensional excitons in carbon nanotubes under high laser excitation.

Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide continuum probe, we show that interband exciton peaks in single-walled carbon nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates of the initial densities of excitons from the excitation conditions, combined with recent theoretical calculations of exciton Bohr radii for SWNTs, suggest that their positions do not change at all even near the Mott density. In addition, we found that the presence of lowest-subband excitons broadens all absorption peaks, including those in the second-subband range, which provides a consistent explanation for the complex spectral dependence of pump-probe signals reported for SWNTs.

Journal Article↗
PubMed2004

Interband recombination dynamics in resonantly excited single-walled carbon nanotubes.

Wavelength-dependent pump-probe spectroscopy of micelle-suspended single-walled carbon nanotubes reveals two-component dynamics. The slow component (5-20 ps), which has not been observed previously, is resonantly enhanced whenever the pump photon energy coincides with an absorption peak and we attribute it to interband carrier recombination, whereas we interpret the always-present fast component (0.3-1.2 ps) as intraband carrier relaxation in nonresonantly excited nanotubes. The slow component decreases drastically with decreasing pH (or increasing H+ doping), especially in large-diameter tubes. This can be explained as a consequence of the disappearance of absorption peaks at high doping due to the entrance of the Fermi energy into the valence band, i.e., a 1D manifestation of the Burstein-Moss effect.

Journal Article↗
PubMed2003

A continuing high incidence of subacute sclerosing panencephalitis (SSPE) in the Eastern Highlands of Papua New Guinea.

The aims of this descriptive study were to confirm the high incidence of subacute sclerosing panencephalitis (SSPE) previously reported from Papua New Guinea (PNG) and to relate SSPE to previous measles vaccination and measles illness. From February 1997 to April 1999 we diagnosed a total of 55 patients with SSPE at Goroka Base General Hospital in Eastern Highlands Province (EHP) of PNG. The diagnosis was based on high cerebrospinal fluid and serum measles virus antibody titres with progressive neurological disorder and myoclonic jerks. Of these 55 patients 42 were from EHP, including 32 whose onset was in the 2-year period 1997-1998. The annual incidence of SSPE in EHP in these 2 years was 98 per million population under 20 years of age, the highest ever reported. This incidence was more than ten times higher than the highest incidence in the prevaccine era reported from elsewhere. The mean age of onset of SSPE was 7.7 years (range 2.8-14.8 years) and the interval between measles and the onset of SSPE, where known, had a mean of 5.9 years and a range of 2.5-11.1 years. Among the SSPE patients 19 had a documented history of measles vaccination. Eight of these 19 also had documentation of previous measles illness; of these, seven were vaccinated after the development of measles and one was vaccinated 20 days before measles illness. Two non-SSPE children received vaccination twice which was documented and subsequently developed measles which was also substantiated by documentation. Two patients with SSPE yielded amplified nucleotide sequences of measles virus that were different from any of the vaccine strains. We found no evidence to implicate measles vaccination in the development of SSPE.

Acute Disease↗
PubMed2001

Extreme midinfrared nonlinear optics in semiconductors.

We have observed extreme nonlinear optical phenomena produced by intense midinfrared (MIR) pulses in semiconductors. These phenomena include multiple off-resonance optical sidebands (up to +/-3 MIR photons interacting with a near-infrared photon), multiple MIR harmonics (up to the seventh harmonic), and significant broadening and modification of MIR harmonic spectra. The generation of these extreme MIR nonlinear optical phenomena is primarily aided by cross-phase modulation.

Journal Article↗
PubMed2001

Nicotine, alcohol, methamphetamine, and inhalant dependence: a comparison of clinical features with the use of a new clinical evaluation form.

The purpose of the present study was to develop a new clinical evaluation form to compare the clinical features of nicotine dependence with those associated with alcohol, methamphetamine, and inhalant dependence. The clinical evaluation form consisted of six scoring items: subjective effects, tolerance, liking (of drug), social disturbance, withdrawal syndrome, and acute psychic and acute physical disorders. A preliminary clinical investigation was performed to test the validity of the evaluation form. Study subjects were those showing dependence on nicotine (n = 25), alcohol (n = 36), methamphetamine (n = 11), and inhalants (n = 6). All subjects met the Diagnostic and Statistical Manual of Mental Disorders (4th ed.) diagnostic criteria for drug dependence, as defined by the Work Group for the chapter "Substance-Related Disorders": M. A. Schuckit, J. E. Helzer, L. B. Cottler, T. Crowley, P. E. Nathan, & G. E. Woody. Nicotine produced subjective effects, tolerance, liking, and psychic withdrawal symptoms, all of which were mild in degree. However, nicotine did not produce social disturbance, physical withdrawal symptoms, or acute psychic or acute physical disorders. With alcohol, acute psychic and acute physical disorders were prominent, and alcohol also produced a moderate degree of influence on various other items that were evaluated. Methamphetamine produced the most serious acute psychic and acute physical disorders with intensive subjective effects. Inhalants were characterized by an intensive degree of acute psychic disorders and subjective effects with mild withdrawal syndrome. Our study findings revealed that the clinical features of drug dependence could be evaluated by using the new clinical evaluation form. Further study is required to clarify the clinical features of nicotine dependence compared with those of other drugs of dependence.

Administration, Inhalation↗
PubMed2000

Ultrafast electroabsorption at the transition between classical and quantum response.

We report the first observation of unusually large induced absorption in semiconductors strongly driven by intense ultrashort midinfrared laser fields. This ultrafast electroabsorption has the largest extent below the band edge ( approximately 1 eV) ever observed, to our knowledge, which we interpret as being a manifestation of the dynamical Franz-Keldysh effect. The electroabsorption is observable when the ponderomotive potential is comparable to the photon energy of the applied field, i.e., when the applied field is at the transition between the classical and quantum regimes.

Journal Article↗
PubMed1998

Cervical lesions related to the systemic progression in rheumatoid arthritis.

STUDY DESIGN: Cross-sectional study of cervical involvement in rheumatoid arthritis. OBJECTIVES: To clarify the correlation between the deterioration of cervical lesions and the systemic progression of rheumatoid arthritis. SUMMARY OF BACKGROUND DATA: The natural course of cervical lesions varies. To date, no systemic parameter has been clarified to predict the progression. METHODS: One hundred seventy-three patients with rheumatoid arthritis participated in this study. The authors studied the progression of cervical lesions and investigated the relation between the types of cervical subluxation at the end of study and the following four variables: the serum level of C-reactive protein, the number of joints with erosion, carpal height ratio, and disease subset (least erosive subset, more erosive subset, and mutilating disease subset). RESULTS: Of the 173 patients, 55 already had cervical subluxation before entering the study. During the follow-up period, 44 patients deteriorated radiographically, and 77 (45%) had cervical involvement, including involvement of upper cervical lesions in 65 patients, upper lesions combined with subaxial subluxation in 10, and subaxial subluxation alone in 2. The upper cervical subluxation progressed in the order of anterior atlantoaxial subluxation, atlantoaxial subluxation combined with vertical subluxation, and vertical subluxation alone. Deterioration of upper cervical lesion and occurrence of subaxial subluxation were closely correlated with an elevation of serum C-reactive protein level, an increase in the number of joints with erosion, and a decrease in the carpal height ratio. The incidence of cervical involvement and the extent of deterioration were different among the disease subsets. CONCLUSIONS: The serum level of C-reactive protein, the number of joints with erosion, and the carpal height ratio correlated closely with the extent of the cervical subluxation. The average C-reactive protein values during the follow-up period correlated with progression of the cervical lesions. The classification of rheumatoid disease subset was useful for predicting the terminal feature of the cervical lesions.

Adolescent↗
PubMed1995

Effect of anaesthetic agents on the phagocytic function of human polymorphonuclear leukocytes through analysis with a phagocytic plaque method.

We examined the effects of the intravenous anaesthetic agents, thiamylal and ketamine, on the phagocytic function of polymorphonuclear leukocytes (PMN) in heparinized peripheral blood from healthy individuals using the phagocytic plaque method. Subclinical doses of thiamylal caused enhancement of the phagocytic activity of PMN and super-clinical doses of thiamylal inhibited phagocytic activity of PMN. Ketamine did not adversely affect phagocytic function at relevant therapeutic concentrations. The results presented in this manuscript indicate the phagocytic plaque method can provide a quantitative assessment of the phagocytic function of leukocytes. This method may prove useful in determining whether anaesthetic agents and other drugs adversely affect leukocyte function and hence help prevent the increased susceptibility to infection which can occur in anaesthetized patients. Conversely, the phagocytic plaque method may prove useful in the search for immune-enhancing drugs.

Adult↗