| JaLCDOI | 10.18926/fest/11422 |
|---|---|
| FullText URL | 011_001_007.pdf |
| Author | Fujita Kazutoshi| Tian Tian Chen| Nishina Tomohiko| Ishikawa, Hirofumi| |
| Abstract | Plasmodium vivax re-emerged in 1993 near the demilitarized zone (DMZ) in South Korea, although P. vivax malaria disappeared in South Korea in 1979. The re-emergence of malaria in South Korea is believed to have originated from infection by mosquitoes from North Korea across the DMZ. The principal vector of P. vivax in the Korean Peninsula is Anopheles sinensis. The density of An. sinensis has a peak during the second week of July. The North Korean strain of P. vivax has 2 characteristics: a wide distribution of the terms of relapse and a high rate of relapse. Therefore, we may well wonder why the incidence of malaria is concentrated in summer, especially in August. Mathematical models in North Korea and South Korea were constructed in which the South Korean model was affected unidirectionally by the North Korean model. We carried out simulations of the model for the Paju-shi and Yonchon-gun situations near the DMZ region. The simulation results followed the time-course of the re-emergence of P. vivax there, and revealed the mechanism of the elevation of the incidence of P. vivax in summer. |
| Keywords | DMZ Korea model Plasmodium vivax re-emergence |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2006-03-15 |
| Volume | volume11 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 7 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 40007297549 |
| JaLCDOI | 10.18926/fest/11423 |
|---|---|
| FullText URL | 012_007_018.pdf |
| Author | Imura Keigo| XiaoDong Wang| Ishikawa, Hirofumi| |
| Abstract | The elliptic curve cryptosystem is a popular cryptosystem. Its safety depends on the difficulty of the elliptic curve discrete logarithm problem (ECDLP). From the viewpoint of ECDLP, it is very interesting to determine the order of elliptic curves. We tabulate the order of elliptic curves on the finite field of characteristic two using the Schoof algorithm, which is an efficient algorithm to decide orders. The Schoof algorithm is carried out by O(log(8)q). Because the calculation of y(q2) occupies most of the time used to execute the Schoof algorithm, it is necessary to reduce the amount of y(q2) calculations. |
| Keywords | elliptic curve order division polynomial Schoof algorithm finite field of characteristic two |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2007-03-15 |
| Volume | volume12 |
| Issue | issue1 |
| Start Page | 7 |
| End Page | 18 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313838 |
| JaLCDOI | 10.18926/fest/11424 |
|---|---|
| FullText URL | 011_009_014.pdf |
| Author | Nishina Tomohiko| Tian Tian Chen| Fujita Kazutoshi| Ishikawa, Hirofumi| |
| Abstract | The red fox (Vulpes vulepes) and the vole ( Clethrionomys refocanus) are principal hosts of Echinococcus multilocularis in Hokkaido, Japan. How protoscoleces increases in voles and the level of immunity in foxes remain unknown because of the lack of survey data, so that it is important to clarify these mecahnisms in order to develop control strategies against E. multilocularis. In this study, the growth of protoscoleces in the infected voles was approximated as the logistic curve, the level of immunity in the fox was assumed to depend on the experience of the infection with E. multilocularis, and the worm burden in the fox was assumed to be governed by the amount of protoscoleces in the vole. Our model showed that the population densities of the hosts and the level of immunity influenced the prevalence of the E. multilocularis. |
| Keywords | Echinococcus multilocularis protoscoleces immunity worm burden stochastic model |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2006-03-15 |
| Volume | volume11 |
| Issue | issue1 |
| Start Page | 9 |
| End Page | 14 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002314034 |
| JaLCDOI | 10.18926/fest/11425 |
|---|---|
| Title Alternative | A mathematical model of Plasmodium falciparum transmission incorporating drug resistance: Simulations of the Solomon Islands situation |
| FullText URL | 012_019_027.pdf |
| Author | Chen, Tiantian| Nishina, Tomohiko| Hisakane, Naoto| Ishikawa, Hirofumi| |
| Abstract | The Solomon Islands are known as a high endemic region of malaria. The resistance of Plasmodium falciparum to chloroquine has been confirmed since 1980 in the Solomon Islands, and the spread of chloroquine resistance is a big hurdle to malaria control. We have constructured the model for P. falciparum making allowance of chloroquine resistance. We distinguish the infection of resistance strains from that of sensitive strains in both the human and the vector populations. Since the overall parasite rate and the parasite rate of gametocytes for P. falciparum are strongly dependent on age, the human population is divided into 7 age groups in the model. The epidemiological parameters are determined by malariological survey in northeastern Guadalcanal (Ishii et al.) and the sporozoite rate in vector population is assumed as 0.1% based on the entomological study (Harada et al.) Our study aims at estimating the effect of mass drug administration under the presence of drug-resistance and also analyzing the escalation of drug-resistance through the transmission model for P. falciparum which can deal with chloroquine resistance. |
| Keywords | Solomon Islands Plasmodium falciparum drug resistance model |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2007-03-15 |
| Volume | volume12 |
| Issue | issue1 |
| Start Page | 19 |
| End Page | 27 |
| ISSN | 1341-9099 |
| language | Japanese |
| File Version | publisher |
| NAID | 120002313858 |
| JaLCDOI | 10.18926/fest/11449 |
|---|---|
| FullText URL | 009_019_026.pdf |
| Author | Sakamura Kenichi| Dong Wang Xiao| Ishikawa, Hirofumi| |
| Abstract | We have investigated the linear cryptanalysis of AES cipher in this article. As the previous encryption standard DES could be broken by the linear cryptanalysis, NIST decided a new encryption standard AES in 2000. We try to analyze one and two rounds AES cipher by the method of the linear cryptanalysis and learn the limits of this mehtod. AES cipher provides a conspicuous difficulty in breaking its keys because of small bias of its S-box. We report the experimental results of success rate and are led to conclusion that this method would not work well on more than 3 rounds to break keys. |
| Keywords | AES Chosen plaintext attack Linear cryptanalysis |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2004-02-27 |
| Volume | volume9 |
| Issue | issue1 |
| Start Page | 19 |
| End Page | 26 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313376 |
| JaLCDOI | 10.18926/fest/11479 |
|---|---|
| FullText URL | 010_001_007.pdf |
| Author | Wang Xiao Dong| Ishikawa, Hirofumi| |
| Abstract | The one-way hash function plays an important role in digital signatures and message authentication from the viewpoint of security. No effective attacking method has been discovered to the algorithm of hash function standard. In this study, we tried to attack SHA-256 in encryption mode using linear and differential cryptanalysis to solve a private key. We deduced that an estimate of the private key would require huge known and chosen plaintexts in both linear and differential cryptanalysis, and that it would be difficult to decipher SHA-256 in view of the required computation. |
| Keywords | differential cryptanalysis encryption mode hash function linear cryptanalysis SHA-256 |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2005-02-28 |
| Volume | volume10 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 7 |
| ISSN | 1341-9099 |
| language | Japanese |
| File Version | publisher |
| NAID | 120002313630 |
| JaLCDOI | 10.18926/fest/11487 |
|---|---|
| FullText URL | 008_001_007.pdf |
| Author | Tsunekuni Yasuhiro| Ohga Yukio| Ishikawa, Hirofumi| |
| Abstract | In 1990s, there were rapid increases in the number of HIV epidemics and AIDS cases in Thailand, Southeast Asia. In particular the risk of HIV infection was very high among female prostitutes who played a large part in the transmission of HIV infection. We formulated a mathematical model for the transmission of HIV in prostitutes. We carried out the model simulations to analyze the incipient spread of HIV infection and the effect of AIDS prevention methods in prostitutes. The simulation of our model indicates that even if the effect of AIDS prevention methods such as the recommendation of condom use for commercial sex workers would block the transmission at rate by 70%, the elimination of the HIV epidemic is still beyond attainment. |
| Keywords | AIDS HIV prostitution Thailand transmission model |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2003-03 |
| Volume | volume8 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 7 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002314019 |
| JaLCDOI | 10.18926/fest/11510 |
|---|---|
| FullText URL | 007_001_005.pdf |
| Author | Ohga, Yukio| Ishikawa, Hirofumi| Doi, Rikuo| Ishii, Hiroyuki| |
| Abstract | In our study, we have investigated the influence of the intermediate host population density on the prevalence of Echinococcus multilocularis in the definitive host using a mathematical model of transmission. For the vole population (intermediate host) in Hokkaido, a model of population dynamics has been constructed in this paper which follows the seasonal and annual fluctuations. In the northeastern area, the vole density appears to fluctuate periodically with a 4 year cycle. The prevalence of Echinococcus multilocularis in the fox population (definitive host) can be affected by the density of vole through the fox ingesting infectious voles. Therefore we have prepared a food habit function of foxes and the logistic distribution has been proposed. The simulations which have been carried out using the mathematical model for transmission of Echinococcus multilocularis together with the vole dynamics have indicated that the prevalence in foxes is correlated and synchronized with the population dynamics of vole. In addition they have also made us recognize that it is necessary to introduce a suitable food habit function into the transmission model. |
| Keywords | Echinococcus multilocularis food habit of foxes Hokkaido population dynamics vole |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2002-03-22 |
| Volume | volume7 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 5 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| JaLCDOI | 10.18926/fest/11512 |
|---|---|
| FullText URL | 007_007_016.pdf |
| Author | Ishii, Hiroyuki| Ishikawa, Hirofumi| Ohga, Yukio| |
| Abstract | We have constructed a stochastic transmission model for lymphatic filariasis caused by Wuchereria bancrofti, and have analyzed its prevalence using computer simulations. In Pondicherry, India, where Wuchereria bancrofti has been spreading, the Vector Control Research Centre has carried out an integrated vector control strategy against malaria and filariasis for five years (1981~1985) with good results reported. Our study was aimed at evaluating the effect of vector control in the context of Pondicherry, and in particular the continuous effect for the post-control period. In this paper, we have used the LYMFASIM model proposed by Plaisier et al., the carrying capacity model by Rochet and the population dynamics model by us. In the LYMFASIM model and the carrying capacity model, we have modified the quantities of parameters in order to fit the models to the parasitological, entomological and epidemiological data in Pondicherry. We have combined the improved LYMFASIM model with the other models. Through simulations of our combinated model, we have compared the prevalence rate in the human population as well as the mean number of L3-larvae in the mosquito population, with and without vector control. As a result, the simulations show that the prevalence rate would be restrained for a long time even if only a small continuous effect of the vector control remains in the post-control period. However, the mean number of L3-larvae would recovered within a short time comparatively. This is because of the differences in life spans between human and mosquito as well as the incubation periods between the adult worm in the human host and L3-larvae in the mosquito vector. |
| Keywords | Lymphatic filariasis mathematical model Pondicherry vector control Wuchereria bancrofti |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2002-03-22 |
| Volume | volume7 |
| Issue | issue1 |
| Start Page | 7 |
| End Page | 16 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313471 |
| JaLCDOI | 10.18926/fest/11548 |
|---|---|
| FullText URL | 005_001_006.pdf |
| Author | Ishikawa, Hirofumi| Ishii, Akira| Kaneko, Akira| |
| Abstract | We have estimated the degree of transmission of Plasmodium vivax malaria in Vanuatu Islands, eastern Melanesia with the aid of the computer simulations, which has been carried out on the platform of a mathematical transmission model. The malaria caused by Plasmodium vivax has a relapse character, which arises from hypnozoites in the liver. This phenomen makes a malaria control strategy difficult. When the mass drug administration is executed, the prevalence of Plasmodium vivax decreases moderately as compared with that of Plasmodium falciparum, and it recovers before long being affected by the relapses. The simulations suggest that one cannot attain the eradication of Plasmodium vivax malaria without the concentrated execution of the mass drug administration and the vector control that fairly reduces the vactorial capacity. |
| Keywords | Plasmodium vivax computer simulation hypnozoite mass drug administration relapse |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2000-02-29 |
| Volume | volume5 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 6 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313438 |
| JaLCDOI | 10.18926/fest/11554 |
|---|---|
| FullText URL | 003_005_009.pdf |
| Author | Ishikawa, Hirofumi| |
| Abstract | We investigate the Maass wave form for Γ(0)(2) whose eigenvalue of Laplacian Δ is 1/4-π(2)/log(2)(√2-1). In this note, we study the methods of calculation of its Fourier coefficients and carry out the numerical calculations. |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 1998-01-14 |
| Volume | volume3 |
| Issue | issue1 |
| Start Page | 5 |
| End Page | 9 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313535 |
| JaLCDOI | 10.18926/fest/11560 |
|---|---|
| FullText URL | 003_031_036.pdf |
| Author | Sasaki, Toru| Kajiwara, Tsuyoshi| Ishikawa, Hirofumi| |
| Abstract | We have computed the phase of spreading contaminations in Kojima Lake by using the upwind-type finite element method. We have treated the two cases: the pollutant flows from the Sasagase river and from the Kurashiki River. We see that the upwind-type finite element method is effective in both cases, when the diffusion constant is quite small. |
| Keywords | Upwind-type Finite element method Kojima Lake |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 1998-01-14 |
| Volume | volume3 |
| Issue | issue1 |
| Start Page | 31 |
| End Page | 36 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313715 |
| JaLCDOI | 10.18926/fest/11595 |
|---|---|
| FullText URL | 002_009_017.pdf |
| Author | Ishikawa, Hirofumi| |
| Abstract | In this paper, we have calculated the elliptic singularities of the symmetric Hilbert modular group defined over a real quadratic number field. Applying those to the dimension formula, we tabulate the dimensions of the space of symmetric Hilbert modular forms of weight two satisfying certain cusp condition. |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 1997-01-10 |
| Volume | volume2 |
| Issue | issue1 |
| Start Page | 9 |
| End Page | 17 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313960 |
| JaLCDOI | 10.18926/fest/11606 |
|---|---|
| FullText URL | 001_027_041.pdf |
| Author | Ishikawa, Hirofumi| |
| Abstract | The author has proved the dimension formula of the space of the Hilbert modular type cusp forms of weight two. We present further refinements of the dimension formula for a real quadratic number field Q(√D), and calculate it effectively. We tabulate the dimensions for square-free natural numbers D below 104 with the computer assistance. We also determine all the spaces of their dimension below 10. |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 1996-03 |
| Volume | volume1 |
| Issue | issue1 |
| Start Page | 27 |
| End Page | 41 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313526 |
| JaLCDOI | 10.18926/fest/11610 |
|---|---|
| FullText URL | 001_047_053.pdf |
| Author | Sasaki, Toru| Ishikawa, Hirofumi| Kajiwara, Tsuyoshi| Watanabe, Masaji| |
| Abstract | We treat the problem of water pollution by the method of a mathematical model. We illustrate the method of analysis with Kojima Lake. We analyze in-flow and out-flow of the lake, compute numerical solutions of the governing equations of the water flow and the pollutant. The simulation leads to the conclusion concerning the figure of Kojima Lake. |
| Keywords | Kojima lake Water analysis Finite element method |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 1996-03 |
| Volume | volume1 |
| Issue | issue1 |
| Start Page | 47 |
| End Page | 53 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002313787 |
| JaLCDOI | 10.18926/fest/12816 |
|---|---|
| Title Alternative | Statistical modeling for analysis of malaria epidemic behavior at Ishigaki Island |
| FullText URL | 13_007_015.pdf |
| Author | Ueki, Masao| Nakagawa, Yuuki| Fueda, Kaoru| Ishikawa, Hirofumi| |
| Abstract | It is necessary to consider a stochastic variability in modeling malaria epidemic behavior since the malaria infection cycle essentially depends on stochastic elements. For this requirement, we need to construct an appropriate statistical model from available data in advance. In this report, we provide some statistical models for the analysis of malaria epidemic behavior at Ishigaki Island. These models can be used for recurrence of past malaria epidemic and prediction of future malaria epidemic at Ishigaki Island. |
| Keywords | Anopheles minimus, generalized liner model Ishigaki Island malaria epidemic behavior prediction stochastic model |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2008-03 |
| Volume | volume13 |
| Issue | issue1 |
| Start Page | 7 |
| End Page | 15 |
| ISSN | 1341-9099 |
| language | Japanese |
| File Version | publisher |
| NAID | 120002304876 |
| JaLCDOI | 10.18926/fest/12819 |
|---|---|
| FullText URL | 13_023_033.pdf |
| Author | Zenihana, Tomohiro| Hisakane, Naoto| Morimoto, Tomoko| Ishikawa, Hirofumi| |
| Abstract | We carried out simulations of various scenarios for bioterrorist attacks using smallpox occurring in a virtual area set up on the basis of the census of Okayama-city, Japan, which predict the effect of control strategies against bioterrorism and the loss scale. On simulating a smallpox epidemic, we followed the method of the Individual Based Model stochastically, which can treat the population in the virtual area as individuals. Individuals have personal information, behavior patterns, and interactions among social groups. We took into consideration the influence of residual immunity due to past vaccination. We considered Traced Vaccination (TV) and Mass Vaccination (MV) strategies against bioterrorism. We investigated the effect of TV and MV strategies on the suppression of smallpox epidemics. Consequently, the TV strategy was found to have higher effectiveness than the MV strategy. |
| Keywords | smallpox bioterrorism Individual Based Model Traced Vaccination Mass Vaccination |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2008-03 |
| Volume | volume13 |
| Issue | issue1 |
| Start Page | 23 |
| End Page | 33 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002304844 |
| JaLCDOI | 10.18926/fest/15042 |
|---|---|
| FullText URL | 014_001_012.pdf |
| Author | Morimoto, Tomoko| Zenihana, Tomohiro| Maitani, Yusuke| Ishikawa, Hirofumi| |
| Abstract | The spread of the highly pathogenic avian influenza (H5N1) among domestic poultry and wild birds has caused global concern over the outbreak of an influenza pandemic of H5N1. The "Pandemic Influenza Preparedness Action Plan" determines the strategy against an influenza pandemic in Japan. Simulations were carried out using an individual based model (IBM). The IBM targeted a virtual area with a population of 100,000 using the demographic data of Sapporo-city, Hokkaido. The effectiveness of targeted antiviral prophylaxis (TAP), geographical targeted antiviral prophylaxis (GTAP), school closure, and pre-pandemic vaccination were explored. Moreover, this study focused on infections among children, who have a high attack rate, and analyzed the effectiveness of interventions for school-age targeted antiviral prophylaxis (STAP). Consequently, TAP, which is recommended by the "Pandemic Influenza Preparedness Action Plan", was found to have high effectiveness in the suppression of the outbreak. Moreover, this study showed the importance of intervention among children, such as STAP and school closure, to prevent the spread of H5N1 influenza. |
| Keywords | Influenza Pandemic H5N1 Individual Based Model (IBM) Sapporo |
| Publication Title | 岡山大学環境理工学部研究報告 |
| Published Date | 2009-03-16 |
| Volume | volume14 |
| Issue | issue1 |
| Start Page | 1 |
| End Page | 11 |
| ISSN | 1341-9099 |
| language | English |
| File Version | publisher |
| NAID | 120002307373 |
| JaLCDOI | 10.18926/AMO/32275 |
|---|---|
| FullText URL | fulltext.pdf |
| Author | Harada, Masakazu| Ishikawa, Hirofumi| Matsuoka, Hiroyuki| Ishii, Akira| Suguri, Setsuo| |
| Abstract | We developed a sensitive polymerase chain reaction (PCR) method for the detection of Plasmodium falciparum DNA from mosquitoes collected in the field. Plasmodium falciparum was detected from 15.2% of 1-parous mosquitoes, Anopheles farauti, in the Solomon Islands through use of the PCR method. A novel mathematical model was developed to estimate the sporozoite rate based on the malaria-positive rate of 1-parous mosquitoes. Using this model, the sporozoite rate of Anopheles farauti in the Solomon Islands was calculated to be 0.09%. This method enables estimation of the sporozoite rate based on a relatively small number (100-200) of mosquitoes compared with the number needed for the ELISA method. |
| Keywords | sporozoite rate polymerase chain reaction (PCR) mathematical model Anopheles Plasmodium |
| Amo Type | Article |
| Publication Title | Acta Medica Okayama |
| Published Date | 2000-08 |
| Volume | volume54 |
| Issue | issue4 |
| Publisher | Okayama University Medical School |
| Start Page | 165 |
| End Page | 171 |
| ISSN | 0386-300X |
| NCID | AA00508441 |
| Content Type | Journal Article |
| language | English |
| File Version | publisher |
| Refereed | True |
| PubMed ID | 10985176 |
| Web of Science KeyUT | 000089132800004 |
| Author | Nishina, Tomohiko| Ishikawa, Hirofumi| |
|---|---|
| Published Date | 2008-02-01 |
| Publication Title | Parasitology Research |
| Volume | volume102 |
| Issue | issue3 |
| Content Type | Journal Article |
