High-rate quantum key distribution over 100 km using ultra-low-noise, 2-GHz sinusoidally gated InGaAs/InP avalanche photodiodes

We have demonstrated quantum key distribution (QKD) over 100 km using single-photon detectors based on InGaAs/InP avalanche photodiodes (APDs). We implemented the differential phase shift QKD (DPS-QKD) protocol with electrically cooled and 2-GHz sinusoidally gated APDs. The single-photon detector has a dark count probability of 2.8 × 10(-8) (55 counts per second) with a detection efficiency of 6 %, which enabled us to achieve 24 kbit/s secure key rate over 100 km of optical fiber. The DPS-QKD system offers better performances in a practical way than those achieved using superconducting single-photon detectors. Moreover, the distance that secure keys against the general individual attacks can be distributed has been extended to 160 km.

Field test of quantum key distribution in the Tokyo QKD Network

A secure communication network with quantum key distribution in a metropolitan area is reported. Six different QKD systems are integrated into a mesh-type network. GHz-clocked QKD links enable us to demonstrate the world-first secure TV conferencing over a distance of 45km. The network includes a commercial QKD product for long-term stable operation, and application interface to secure mobile phones. Detection of an eavesdropper, rerouting into a secure path, and key relay via trusted nodes are demonstrated in this network.

Efficient entanglement distribution over 200 kilometers

Here we report the first demonstration of entanglement distribution over a record distance of 200 km which is of sufficient fidelity to realize secure communication. In contrast to previous entanglement distribution schemes, we use detection elements based on practical avalanche photodiodes (APDs) operating in a self-differencing mode. These APDs are low-cost, compact and easy to operate requiring only electrical cooling to achieve high single photon detection efficiency. The self-differencing APDs in combination with a reliable parametric down-conversion source demonstrate that entanglement distribution over ultra-long distances has become both possible and practical. Consequently the outlook is extremely promising for real world entanglement-based communication between distantly separated parties.

Long-distance entanglement-based quantum key distribution over optical fiber

We report the first entanglement-based quantum key distribution (QKD) experiment over a 100-km optical fiber. We used superconducting single photon detectors based on NbN nanowires that provide high-speed single photon detection for the 1.5-mum telecom band, an efficient entangled photon pair source that consists of a fiber coupled periodically poled lithium niobate waveguide and ultra low loss filters, and planar lightwave circuit Mach-Zehnder interferometers (MZIs) with ultra stable operation. These characteristics enabled us to perform an entanglement-based QKD experiment over a 100-km optical fiber. In the experiment, which lasted approximately 8 hours, we successfully generated a 16 kbit sifted key with a quantum bit error rate of 6.9 % at a rate of 0.59 bits per second, from which we were able to distill a 3.9 kbit secure key.

Differential-phase-shift quantum secret sharing

A quantum secret sharing (QSS) protocol based on a differential-phase-shift scheme is proposed, which quantum mechanically provides a full secret key to one party and partial keys to two other parties. A weak coherent pulse train is utilized instead of individual photons as in conventional schemes. Compared with previous QSS protocols, the present one features a simple setup, is suitable for fiber transmission, and offers the possibility for a high key creation rate. An experiment is also carried out to demonstrate the operation.

Efficient and low-noise single-photon detection in 1550 nm communication band by frequency upconversion in periodically poled LiNbO3 waveguides

We demonstrate 1500 nm band single-photon detection with low dark-count noise and a potentially high efficiency, which may allow long distance and high-bit-rate quantum key distribution. By developing frequency upconversion devices based on periodically poled lithium niobate waveguides, which are specifically designed to use a pump wavelength longer than that of communication-band photons, we completely eliminate the dark-count noise caused by parasitic nonlinear processes in the waveguide. We observed an internal conversion efficiency as high as 40% and demonstrated scaling down to the single photon level while maintaining a background dark-count rate of 10(2)s(-1).

Long-distance distribution of time-bin entangled photon pairs over 100 km using frequency up-conversion detectors

We report an experimental demonstration of the distribution of time-bin entangled photon pairs over 100 km of optical fiber. In our experiment, 1.5-mum non-degenerated time-bin entangled photon pairs were generated with a periodically poled lithium niobate (PPLN) waveguide by using the parametric down conversion process. Combining this approach with ultra-low-loss filters to eliminate the pump light and separate signal and idler photons, we obtained an efficient entangled photon pair source. To detect the photons, we used single-photon detectors based on frequency up-conversion. These detectors operated in a non-gated mode so that we could use a pulse stream of time correlated entangled photon pairs at a high repetition frequency (1 GHz). Using these elements, we distributed time-bin entangled photon pairs over 100 km of dispersion shifted fiber and performed a two-photon interference experiment. We obtained a coincidence fringe of 81.6% visibility without subtracting any background noise, such as accidental coincidence or dark count, which was good enough to violate Bell's inequality. Thus, we successfully distributed time-bin entangled photon pairs over 100 km.

Generation of energy-time entangled photon pairs in 1.5-mum band with periodically poled lithium niobate waveguide

We report the generation of 1.5-mm-band energy-time entangled photon pairs using a periodically poled lithium niobate (PPLN) waveguide. We performed a two-photon interference experiment and obtained coincidence fringes with 77.3% visibilities without subtracting accidental coincidences.

Inhibition of metastatic carcinoma cell growth in livers by poly(I):poly(C)/cationic liposome complex (LIC)

The complex of poly(I):poly(C) and a new cationic liposome (LIC) has a potent antitumor activity against many tumor cell lines in vitro, whereas poly(I):poly(C) itself has no such activity. In the present study we tested the sensitivity of 21 human colon and pancreatic cancer cell lines to LIC or Adriamycin in vitro. The growth of most of the cell lines was strongly inhibited by both LIC and Adriamycin in vitro, although a few insensitive cell lines were different. We also studied the in vivo antitumor activity of LIC or Adriamycin in three experimental liver metastasis models in nude mice using a human pancreatic cancer cell line (AsPC-1) and two human colon cancer cell lines (Ls174T and HCC-M1544). The administration of LIC or Adriamycin was started 3 days after the injection of tumor cells. Animals received 0.1 mg/kg LIC IV twice weekly or 5 mg/kg Adriamycin IV every 5 days during the experiments. LIC showed potent antitumor activity in all three liver cancer models. Although Adriamycin had potent antitumor activity in the HCC-M1544 model, it had only a moderate effect in the AsPC-1 model and at most a weak effect in the Ls174T model. At the effective doses LIC did not cause detectable pathological changes in the liver and did not elicit toxicity to mice in these models, whereas Adriamycin did exhibit toxic effects. These results suggest that LIC is a promising candidate drug to treat hepatic metastasis.

Purification and characterization of intracellular alpha-L-rhamnosidase from Pseudomonas paucimobilis FP2001

alpha-L-Rhamnosidase was extracted and purified from the cells of Pseudomonas paucimobilis FP2001 with a 19.5% yield. The purified enzyme, which was homogeneous as shown by SDS-PAGE and isoelectric focusing, had a molecular weight of 112,000 and an isoelectric point of 7.1. The enzyme activity was accelerated by Ca2+ and remained stable for several months when stored at -20 C. The optimum pH was 7.8; the optimum temperature was 45 degrees C. The Km, V(max) and k(cat) for p-nitrophenyl alpha-L-rhamnopyranoside were 1.18 mM, 92.4 microM x min(-1) and 117,000 x min(-1), respectively. Examination of the substrate specificity using various synthetic and natural L-rhamnosyl glycosides showed that this enzyme had a relatively broader substrate specificity than those reported so far.

A novel Ca2+/calmodulin-dependent protein kinase lacking autophosphorylation activity in the rabbit heart

We report the discovery, semi-purification and characterization of a novel Ca2+/calmodulin-dependent protein kinase (peak I kinase) using syntide 2 as a substrate from the rabbit heart. In the study of dependence of peak I kinase on the concentration of calmodulin, half-maximal activation was obtained at approx. 2.0 x 10(-7) M calmodulin. Peak I kinase did not undergo autophosphorylation. This kinase phosphorylates the synthetic peptides such as syntide 2, autocamtide-2, site 3 in a Ca2+/CaM-dependent manner, but not myosin light chain-peptide, gamma-peptide, and cAMP Response Element Binding Protein (CREB) peptide. Elongation Factor-2, alpha-casein and histone-IIIs were not phosphorylated. These data indicate that this CaM kinase is different from other identified Ca2+/calmodulin-dependent protein kinases and therefore constitutes a novel protein kinase.

A novel low molecular weight factor detected in the cytosol of guinea pig neutrophils to enhance superoxide anion production

Cytosolic low molecular components in guinea pig neutrophils were examined for the activity to enhance superoxide anion (O2-)-generating NADPH oxidase activity. A component was separated by Sephadex G-25 gel filtration from high molecular weight components, the latter revealed NADPH oxidase activity in a cell-free system in combination with the membrane fraction and arachidonic acid. Addition of this cytosolic low molecular weight component to the cell-free system significantly enhanced NADPH oxidase activity, though this component did not substitute the high molecular weight components in constituting the system. The low molecular weight NADPH oxidase activation factor (LMWAF) found here was not of protein nature, since protease treatment failed to reduce its activity. This factor did not contain phosphate, and was neither flavin nor guanine nucleotide. Though LMWAF was extractable with chloroform-methanol, it was not identical with diacylglycerol.

Stimulation of superoxide anion production in guinea pig polymorphonuclear leukocytes by hypotonic conditions in combination with protein kinase C activators

Conditions for superoxide anion (O2-) production were examined in guinea pig polymorphonuclear leukocytes (PMNL). When PMNL were suspended in the hypotonic medium, O2- production was significantly enhanced by concurrent treatment with low concentrations of 1-oleoyl-2-acetylglycerol (OAG), a cell-permeable protein kinase C activator. Such hypotonicity or OAG alone had little effect on the production. Other protein kinase C activators also markedly enhanced O2- production in combination with hypotonicity, but not in the isotonic medium. Protein kinase C inhibitors, H-7 and staurosporine, dose-dependently inhibited the production. These observations indicate that protein kinase C participates in such synergistic O2- production with hypotonicity. Phosphorylation of 46-kDa protein(s), which was commonly enhanced in paralleled with an activation of NADPH oxidase in guinea pig PMNL, was increased by treatment with 10 microM OAG, but the phosphorylation was little altered by hypotonic treatment. Intracellular calcium concentration, arachidonate release, and 1,2-diacylglycerol and phosphoinositide concentrations were slightly altered by hypotonic treatment. A change in phosphatidate (PA) production in PMNL was induced by hypotonic treatment either by itself or in combination with OAG treatment. These results suggest that the combination of cell membrane changes by hypotonic treatment accompanied by the increase in PA and 46-kDa protein phosphorylation by protein kinase C provides the conditions required for a marked increase in O2- production. Hypotonicity may be a good tool for studying the mechanism of priming in the activation of NADPH oxidase.

[Pharmacology of a new sleep inducer, 1H-1,2,4-triazolyl benzophenone derivative, 450191-S (II). Sleep-inducing activity and effect on the motor system]

The sleep-inducing activity and effect on the motor system of the 1H-1,2,4-triazolyl benzophenone derivative 450191-S were examined behaviorally, electroencephalographically and electro-physiologically with various species of animals and were compared with those of diazepam, nitrazepam, estazolam and triazolam. In the rhesus monkey, rabbit and rat with chronically indwelling brain electrodes, 0.6 to 3 mg/kg, p.o. of 450191-S caused a shorter latency of sleep onset, an increase of and a stable continuity of slow wave deep sleep (SWDS) with higher amplitude, and the appearance of clear spindle bursts in the slow wave light sleeping (SWLS) state with little muscle relaxation. Animals treated with nitrazepam and/or estazolam showed a smaller increase in SWDS and its unstable continuity with remarkable disturbance of gait. The doses needed to induce sleep in the rhesus monkey were 0.6 to 1 mg/kg p.o. for 450191-S, 3 mg/kg for nitrazepam, 1 mg/kg for estazolam and 0.3 mg/kg for triazolam. The cat treated with 450191-S showed the phenomena caused by benzodiazepines (BDZ), i.e., behavioral excitation and decrease of frequencies in the hippocampal theta waves. The suppressive effects of 450191-S on the EEG arousal reaction and/or blood pressure elevation induced by hypothalamic stimulation in the rabbit suggested that the inhibitory effects acted on the posterior hypothalamus to the limbic system. The inhibitory effect of 450191-S on the amygdaloid kindling in the rat was as potent as those of diazepam and nitrazepam. Successive daily oral administration of both 3 mg/kg of 450191-S and/or 3 to 6 mg/kg of nitrazepam for 15 days in the rabbit caused slight decrease of SWDS and increase of fast wave (REM) sleep (FWS). During the withdrawal period of both compounds, a slight but insignificant increase in the waking state was noticed for 1 to 2 days, but not a rebound increase of FWS. Intravenously administered 450191-S showed the same action as BDZ on the spinal reflex and the dorsal root potential of the rat; it particularly acted on the crossed extensor reflex in the same manner as the commercial BDZ sleep inducers.(ABSTRACT TRUNCATED AT 400 WORDS)

Difference in urinary N-acetyl-beta-D-glucosaminidase activity between male and female beagle dogs

Urinary N-acetyl-beta-D-glucosaminidase (NAG) activity differed greatly between male and female beagle dogs in an age-matched group. The NAG activity in males per animal, per body weight, or per 16-hour urine sample was approximately double that in females and was 2.4-fold higher when the activity was considered relative to urinary creatinine. On the other hand, alanine aminopeptidase activity relative to urinary creatinine was not significantly different between males and females. These findings indicate that when using urinary NAG activity to detect drug nephrotoxicity in dogs, some consideration must be given to different control levels between males and females before starting drug administration.