The Octonions

The octonions are the largest of the four normed division algebras. While somewhat neglected due to their nonassociativity, they stand at the crossroads of many interesting fields of mathematics. Here we describe them and their relation to Clifford algebras and spinors, Bott periodicity, projective and Lorentzian geometry, Jordan algebras, and the exceptional Lie groups. We also touch upon their applications in quantum logic, special relativity and supersymmetry.Comment: 56 pages LaTeX, 11 Postscript Figures, some small correction

Transcatheter Arterial Chemoembolization of Hepatocellular Carcinoma: Prevalence and Causative Factors of Extrahepatic Collateral Arteries in 479 Patients

OBJECTIVE: We wanted to investigate the prevalence and causative factors of extrahepatic arterial blood supply to hepatocellular carcinoma (HCC) at its initial presentation and during chemoembolization. MATERIALS AND METHODS: Between February 1998 and April 2000, consecutive 479 patients with newly diagnosed HCC were prospectively enrolled into this study. A total of 1629 sessions of transcatheter arterial chemoembolization (TACE) were performed in these patients (range: 1-15 sessions; mean: 3.4 sessions) until April 2004. For each TACE procedure, we determined the potential extrahepatic collateral arteries (ExCAs) depending on the location of the tumor, and we performed selective angiography of all suspected collaterals that could supply the tumor. The prevalence of ExCAs and the causative factors were analyzed. RESULTS: At initial presentation, 82 (17%) of these 479 patients showed 108 ExCAs supplying tumors. Univariate analysis showed that tumor size (p or =5 cm) was significantly higher than that for those patients with a small tumor (< 5 cm) (p < 0.01). CONCLUSION: The presence of ExCAs supplying HCC is rather common, and the tumor size is a significant causative factor for the development of these collateral arteries.This study was supported by a grant (0620220-1) from the National R & D Program for Cancer Control, Ministry of Health & Welfare, Republic of Korea

Packet scheduling in the presence of channel estimation error in multi-user OFDM wireless systems

In this paper, we investigate the effect of channel estimation error on the performance of channel aware techniques in a packet-based multi-user OFDM wireless system. To this end, we consider the use of two channel estimation schemes; one is a simple linear and the other is an optimum Wiener-type channel estimator. We examine the effect of channel impulse response (CIR) estimation error on coherent reception and the effect of signal-to-interference and noise ratio (SINR) estimation error on channel aware transmission techniques (e.g., packet scheduling). It is shown that the performance of coherent reception is relatively less susceptible to the CIR estimation error, but the performance of channel aware schemes can be very sensitive to the SINR estimation error. To alleviate this problem, we propose a robust scheduling scheme which can work without significant performance degradation even in the presence of large channel estimation error. Finally, we verify the performance of the proposed scheduling scheme by computer simulation.Ministry of Information & Communications, Kore

Zero-frequency Bragg gap by spin-harnessed metamaterial

The Bragg gap that stops wave propagation may not be formed from zero or a very low frequency unless the periodicity of a periodic system is unrealistically large. Accordingly, the Bragg gap has been considered to be inappropriate for low frequency applications despite its broad bandwidth. Here, we report a new mechanism that allows formation of the Bragg gap starting from a nearly zero frequency. The mechanism is based on the finding that if additional spin motion is coupled with the longitudinal motion of a mass of a diatomic mechanical periodic system, the Bragg gap starting from a nearly zero frequency can be formed. The theoretical analysis shows that the effective mass and stiffness at the band gap frequencies are all positive, confirming that the formed stop band is a Bragg gap. The periodic system is realized by a spin-harnessed metamaterial which incorporates unique linkage mechanisms. The numerical and experimental validation confirmed the formation of the low-frequency Bragg gap. The zero-frequency Bragg gap is expected to open a new way to control hard-to-shield low-frequency vibration and noise

Epidemiology of Foodborne Norovirus Outbreak in Incheon, Korea

On June 14, 2008, an outbreak of gastroenteritis occurred among elementary school students in Incheon. We conducted an investigation to identify the source and described the extent of the outbreak. We performed a retrospective cohort study among students, teachers and food handlers exposed to canteen food in the elementary school. Using self-administered questionnaires we collected information on symptoms, days of canteen food eaten, food items consumed. Stool samples were collected from 131 symptomatic people and 11 food handlers. The catering kitchen was inspected and food samples were taken. Of the 1,560 people who ate canteen food, 117 were symptomatic cases, and the attack rate was 7.5%. Consumption of cucumber-crown daisy salad (RR=2.71), fresh cabbage mix (RR=2.23), dried radish salad (RR=3.04) and young radish kimchi (RR=2.52) were associated with illness. Sixty-four (45%) of the 142 stool specimens were positive for Norovirus. Norovirus was detected in 2 food handlers. Interviews with kitchen staff indicated the likelihood of contamination from an infected food handler to the dried radish salad during food processing. The excretion of Norovirus from asymptomatic food handlers may be an infection source of Norovirus outbreaks

Radiographic comparison between cervical spine lateral and whole-spine lateral standing radiographs

Study Design Retrospective radiologic study. Objective The sagittal alignment of the cervical spine can be evaluated using either a lateral cervical radiograph or a whole-spine lateral view on which the cervical spine is included. To our knowledge, however, no report has compared the two. The purpose of this work is to identify the difference in radiographic parameters between the cervical spine lateral view and the whole-spine lateral view. Methods We retrospectively analyzed 59 adult patients suffering from neck pain with cervical spine lateral radiographs and whole-spine lateral radiographs from November 2007 to December 2011. The radiographs were measured using standard techniques to obtain the following parameters from the two different radiographs: occipital–C2 angle, C2–C7 angle, C7–sternal angle, sternal slope, T1 slope, C2 central offset distance, the distance between C2 and C7 plumb lines, C4 anteroposterior (AP) diameter, the ratio of C2 central off distance to C4 AP diameter, the ratio of plumb lines' distance to C4 AP diameter. Results We found that the occipital–C2 angle, sternal slope, and C4 AP diameter were similar, but the C2–C7 angle, C7–sternal angle, T1 slope, C2 central offset distance, distance between C2 and C7 plumb lines, ratio of C2 central off distance to C4 AP diameter, and ratio of plumb lines' distance to C4 AP diameter were different. However, the error of measurement was greater than the small angular and linear differences between the two views. Conclusions Most numerical values of the measured radiographic parameters appear to be different between the two views. However, the two views are comparable because the numerical differences were smaller than the errors of measurement

A new technique for superselective catheterization of arteries: preshaping of a micro-guide wire into a shepherd's hook form

OBJECTIVE: We wanted to introduce a new technique for superselective catheterization of arteries with preshaping of a micro-guide wire into a shepherd's hook form, and this is useful for superselection of small arteries branching at an acute angle from a large parent artery for the treatment of tumors and hemorrhages. MATERIALS AND METHODS: We developed a superselective catheterization technique by using preshaping of a micro-guide wire into a shepherd's hook form. We encountered six patients in our practice for whom we failed to catheterize the small tumor-feeding arteries that branched at an acute angle from wide parent arteries during chemoembolization of hepatocellular carcinoma; the parent arteries were the right inferior phrenic artery (n = 4) and the left gastric artery (n = 1) from the celiac axis with celiac stenosis due to compression by the median arcuate ligament and the proper hepatic artery from the gastroduodenal artery (n = 1) in a patient who had celiac axis occlusion with collateral circulation via the pancreaticoduodenal arcade from the superior mesenteric artery. In these consecutive six patients, we tested the usefulness of this new technique with employing preshaping of a micro-guide wire into a shepherd's hook form for superselective catheterization of targeted vessels. RESULTS: The target arteries were successfully catheterized and satisfactory transcatheter arterial chemoembolization was performed in all six patients. There were no significant complications such as arterial dissection. CONCLUSION: We developed a technique that is effective for superselection of vessels with preshaping of micro-guide wire into a shepherd's hook form, and we successfully applied it during chemoembolization of hepatocellular carcinoma. This technique can be useful for superselection of small arteries that branch from a large parent artery at acute angles for the treatment of tumors and hemorrhages

A new technique for superselective catheterization of arteries: preshaping of a micro-guide wire into a shepherd's hook form

OBJECTIVE: We wanted to introduce a new technique for superselective catheterization of arteries with preshaping of a micro-guide wire into a shepherd's hook form, and this is useful for superselection of small arteries branching at an acute angle from a large parent artery for the treatment of tumors and hemorrhages. MATERIALS AND METHODS: We developed a superselective catheterization technique by using preshaping of a micro-guide wire into a shepherd's hook form. We encountered six patients in our practice for whom we failed to catheterize the small tumor-feeding arteries that branched at an acute angle from wide parent arteries during chemoembolization of hepatocellular carcinoma; the parent arteries were the right inferior phrenic artery (n = 4) and the left gastric artery (n = 1) from the celiac axis with celiac stenosis due to compression by the median arcuate ligament and the proper hepatic artery from the gastroduodenal artery (n = 1) in a patient who had celiac axis occlusion with collateral circulation via the pancreaticoduodenal arcade from the superior mesenteric artery. In these consecutive six patients, we tested the usefulness of this new technique with employing preshaping of a micro-guide wire into a shepherd's hook form for superselective catheterization of targeted vessels. RESULTS: The target arteries were successfully catheterized and satisfactory transcatheter arterial chemoembolization was performed in all six patients. There were no significant complications such as arterial dissection. CONCLUSION: We developed a technique that is effective for superselection of vessels with preshaping of micro-guide wire into a shepherd's hook form, and we successfully applied it during chemoembolization of hepatocellular carcinoma. This technique can be useful for superselection of small arteries that branch from a large parent artery at acute angles for the treatment of tumors and hemorrhages

Bioconversion of CO to formate by artificially designed carbon monoxide:formate oxidoreductase in hyperthermophilic archaea

Ferredoxin-dependent metabolic engineering of electron transfer circuits has been developed to enhance redox efficiency in the field of synthetic biology, e.g., for hydrogen production and for reduction of flavoproteins or NAD(P)+. Here, we present the bioconversion of carbon monoxide (CO) gas to formate via a synthetic CO:formate oxidoreductase (CFOR), designed as an enzyme complex for direct electron transfer between non-interacting CO dehydrogenase and formate dehydrogenase using an electron-transferring Fe-S fusion protein. The CFOR-introduced Thermococcus onnurineus mutant strains showed CO-dependent formate production in vivo and in vitro. The maximum formate production rate from purified CFOR complex and specific formate productivity from the bioreactor were 2.2????????0.2 ??mol/mg/min and 73.1????????29.0 mmol/g-cells/h, respectively. The CO-dependent CO2 reduction/formate production activity of synthetic CFOR was confirmed, indicating that direct electron transfer between two unrelated dehydrogenases was feasible via mediation of the FeS-FeS fusion protein