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Biomedical subjects

Yoshihisa Yamamoto

Publications and source records attributed to Yoshihisa Yamamoto.

7 recordsLinked to original sources
PubMed2002

Pharmacological characterization of alpha1-adrenoceptor in mouse iliac artery.

Subtypes of alpha(1)-adrenoceptor-mediated contraction to noradrenaline in the mouse iliac artery were determined (pharmaco-mechanically). Prazosin, 2-[2,6-dimethoxyphenoxyethyl]aminomethyl-1,4-benzodioxane hydrochloride (WB 4101) and 5-methylurapidil shifted the concentration-response curve for noradrenaline to the right, giving the pA(2) values of 9.30, 9.55 and 8.71, respectively. 8-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]-ethyl]-8-azaspiro[4,5]decane-7,9-dione dihydrochloride (BMY 7378) shifted the concentration-response curve for noradrenaline to the right and the pA(2) value was 6.62. These results indicate that the contractile response to noradrenaline in the mouse iliac artery is predominantly mediated by the alpha(1A) -adrenoceptor subtype.

Adrenergic alpha-1 Receptor Agonists↗
PubMed2002

Efficient source of single photons: a single quantum dot in a micropost microcavity.

We have demonstrated efficient production of triggered single photons by coupling a single semiconductor quantum dot to a three-dimensionally confined optical mode in a micropost microcavity. The efficiency of emitting single photons into a single-mode traveling wave is approximately 38%, which is nearly 2 orders of magnitude higher than for a quantum dot in bulk semiconductor material. At the same time, the probability of having more than one photon in a given pulse is reduced by a factor of 7 as compared to light with Poissonian photon statistics.

Journal Article↗
PubMed2002

Indistinguishable photons from a single-photon device.

Single-photon sources have recently been demonstrated using a variety of devices, including molecules, mesoscopic quantum wells, colour centres, trapped ions and semiconductor quantum dots. Compared with a Poisson-distributed source of the same intensity, these sources rarely emit two or more photons in the same pulse. Numerous applications for single-photon sources have been proposed in the field of quantum information, but most--including linear-optical quantum computation--also require consecutive photons to have identical wave packets. For a source based on a single quantum emitter, the emitter must therefore be excited in a rapid or deterministic way, and interact little with its surrounding environment. Here we test the indistinguishability of photons emitted by a semiconductor quantum dot in a microcavity through a Hong-Ou-Mandel-type two-photon interference experiment. We find that consecutive photons are largely indistinguishable, with a mean wave-packet overlap as large as 0.81, making this source useful in a variety of experiments in quantum optics and quantum information.

Journal Article↗
PubMed2002

Condensation of semiconductor microcavity exciton polaritons.

A phase transition from a classical thermal mixed state to a quantum-mechanical pure state of exciton polaritons is observed in a GaAs multiple quantum-well microcavity from the decrease of the second-order coherence function. Supporting evidence is obtained from the observation of a nonlinear threshold behavior in the pump-intensity dependence of the emission, a polariton-like dispersion relation above threshold, and a decrease of the relaxation time into the lower polariton state. The condensation of microcavity exciton polaritons is confirmed.

Journal Article↗
PubMed2002

Mixed peripheral blood stem cell transplantation for autoimmune disease in BXSB/MpJ mice.

We examined whether mixed allogeneic transplantation with syngeneic plus allogeneic peripheral blood stem cells (PBSCs) is sufficient to interrupt autoimmune processes in BXSB mice and confer a potential therapeutic option for the treatment of patients with autoimmune diseases. Eight-week-old BXSB mice were lethally irradiated and reconstituted with BALB/c (H-2(d))+BXSB (H-2(b)) PBSCs, in which the number of injected allogeneic progenitor cells was 5 times that of syngeneic progenitor cells. The survival of mixed PBSC chimeras (BALB/c+BXSB-->BXSB) was 80% at the age of 48 weeks, whereas that of full chimeras (BALB/c-->BXSB) was 90%. Mixed PBSC transplantation (PBSCT) prevented the production of anti-DNA antibodies and the development of lupus nephritis in BXSB recipients and induced tolerance to both allogeneic and syngeneic antigens. Moreover, mixed chimeras exhibited immunological functions superior to fully allogeneic chimeras. On the other hand, increases in the number of BXSB PBSCs resulted in the transfer of lupus nephritis in BXSB+BALB/c-->BALB/c mice. Thus, the number of hematopoietic progenitor cells from normal mice proved critical to the prevention of autoimmune diseases. We propose that mixed allogeneic PBSCT for the interruption of the autoimmune process can be carried out by injecting increased numbers of allogeneic normal hematopoietic progenitor cells to prevent the relapse of autoimmune diseases, although it is necessary to decide upon a minimum dose of syngeneic PBSCs to achieve the desired beneficial effects on autoimmunity.

Animals↗
PubMed2002

Differential phase shift quantum key distribution.

A novel quantum cryptography scheme is proposed, in which a single photon is prepared in a linear superposition state of three basis kets. A photon split to three pulses is sent from Alice to Bob, where the phase difference between sequential two pulses carries bit information. Bob measures the phase difference by passive differential phase detection. This scheme is suitable for fiber transmission systems and offers a key creation efficiency higher than conventional fiber-based BB84.

Journal Article↗