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Natural Numbers and the Strong Goldbach Conjecture
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作者 Ramon Carbó-Dorca 《Journal of Applied Mathematics and Physics》 2024年第9期3208-3236,共29页
This study introduces the representation of natural number sets as row vectors and pretends to offer a new perspective on the strong Goldbach conjecture. The natural numbers are restructured and expanded with the incl... This study introduces the representation of natural number sets as row vectors and pretends to offer a new perspective on the strong Goldbach conjecture. The natural numbers are restructured and expanded with the inclusion of the zero element as the source of a strong Goldbach conjecture reformulation. A prime Boolean vector is defined, pinpointing the positions of prime numbers within the odd number sequence. The natural unit primality is discussed in this context and transformed into a source of quantum-like indetermination. This approach allows for rephrasing the strong Goldbach conjecture, framed within a Boolean scalar product between the prime Boolean vector and its reverse. Throughout the discussion, other intriguing topics emerge and are thoroughly analyzed. A final description of two empirical algorithms is provided to prove the strong Goldbach conjecture. 展开更多
关键词 Natural numbers Prime numbers Vector Description of Natural numbers Prime Boolean Vectors Primality of the Natural Unit strong Goldbach’s Conjecture Vector Reversal Pairing Conjecture Natural Matrix squeezing
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Identities on q-Harmonic Numbers
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作者 Mengxiao Zhou Haitao Jin Huanhuan Zheng 《Journal of Applied Mathematics and Physics》 2024年第5期1796-1803,共8页
With the help of the classical Abel’s lemma on summation by parts and algorithm of q-hypergeometric summations, we deal with the summation, which can be written as multiplication of a q-hypergeometric term and q-harm... With the help of the classical Abel’s lemma on summation by parts and algorithm of q-hypergeometric summations, we deal with the summation, which can be written as multiplication of a q-hypergeometric term and q-harmonic numbers. This enables us to construct and prove identities on q-harmonic numbers. Several examples are also given. 展开更多
关键词 Harmonic numbers q-Zeilberger Algorithm Abel’s Lemma
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On Some Mathematical Connections between the Cyclic Universe, Inflationary Universe, p-Adic Inflation, p-Adic Cosmology and Various Sectors of Number Theory
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作者 Michele Nardelli 《Journal of Modern Physics》 2024年第11期1869-1958,共90页
This paper is a review, a thesis, of some interesting results that have been obtained in various research concerning the “brane collisions in string and M-theory” (Cyclic Universe), p-adic inflation and p-adic cosmo... This paper is a review, a thesis, of some interesting results that have been obtained in various research concerning the “brane collisions in string and M-theory” (Cyclic Universe), p-adic inflation and p-adic cosmology. In Section 2, we have described some equations concerning cosmic evolution in a Cyclic Universe. In Section 3, we have described some equations concerning the cosmological perturbations in a Big Crunch/Big Bang space-time, the M-theory model of a Big Crunch/Big Bang transition and some equations concerning the solution of a braneworld Big Crunch/Big Bang Cosmology. In Section 4, we have described some equations concerning the generating ekpyrotic curvature perturbations before the Big Bang, some equations concerning the effective five-dimensional theory of the strongly coupled heterotic string as a gauged version of N=1five-dimensional supergravity with four-dimensional boundaries, and some equations concerning the colliding branes and the origin of the Hot Big Bang. In Section 5, we have described some equations regarding the “null energy condition” violation concerning the inflationary models and some equations concerning the evolution to a smooth universe in an ekpyrotic contracting phase with w>1. In Section 6, we have described some equations concerning the approximate inflationary solutions rolling away from the unstable maximum of p-adic string theory. In Section 7, we have described various equations concerning the p-adic minisuperspace model, zeta strings, zeta nonlocal scalar fields and p-adic and adelic quantum cosmology. In Section 8, we have shown various and interesting mathematical connections between some equations concerning the p-adic inflation, the p-adic quantum cosmology, the zeta strings and the brane collisions in string and M-theory. Furthermore, in each section, we have shown the mathematical connections with various sectors of Number Theory, principally the Ramanujan’s modular equations, the Aurea Ratio and the Fibonacci’s numbers. 展开更多
关键词 string Theory M-THEORY Cyclic Cosmology p-Adic and Adelic Analysis number Theory Ramanujan’s Modular Equations
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On Prime Numbers between kn and (k + 1) n
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作者 Wing K. Yu 《Journal of Applied Mathematics and Physics》 2023年第11期3712-3734,共23页
In this paper along with the previous studies on analyzing the binomial coefficients, we will complete the proof of a theorem. The theorem states that for two positive integers n and k, when n ≥ k - 1, there always e... In this paper along with the previous studies on analyzing the binomial coefficients, we will complete the proof of a theorem. The theorem states that for two positive integers n and k, when n ≥ k - 1, there always exists at least a prime number p such that kn p ≤ (k +1)n. The Bertrand-Chebyshev’s theorem is a special case of this theorem when k = 1. In the field of prime number distribution, just as the prime number theorem provides the approximate number of prime numbers relative to natural numbers, while the new theory indicates that prime numbers exist in the specific intervals between natural numbers, that is, the new theorem provides the approximate positions of prime numbers among natural numbers. 展开更多
关键词 Bertrand’s Postulate-Chebyshev’s Theorem The Prime number Theorem Landau Problems Legendre’s Conjecture Prime number Distribution
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Products of Odd Numbers or Prime Number Can Generate the Three Members’ Families of Fermat Last Theorem and the Theorem Is Valid for Summation of Squares of More Than Two Natural Numbers
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作者 Susmita Pramanik Deepak Kumar Das Panchanan Pramanik 《Advances in Pure Mathematics》 2023年第10期635-641,共7页
Fermat’s last theorem, had the statement that there are no natural numbers A, B, and C such that A<sup>n</sup> + B<sup>n</sup> = C<sup>n</sup>, in which n is a natural number great... Fermat’s last theorem, had the statement that there are no natural numbers A, B, and C such that A<sup>n</sup> + B<sup>n</sup> = C<sup>n</sup>, in which n is a natural number greater than 2. We have shown that any product of two odd numbers can generate Fermat or Pythagoras triple (A, B, C) following n = 2 and also it is applicable A<sup>2</sup> + B<sup>2</sup> + C<sup>2</sup> + D<sup>2</sup> + so on =A<sub>n</sub><sup>2 </sup>where all are natural numbers. 展开更多
关键词 Fermat Last Theorem Generation of Fermat’s numbers Extension of Fermat’s Expression Fermat’s Expression from Products of Odd numbers
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Very Original Proofs of Two Famous Problems: “Are There Any Odd Perfect Numbers?” (Unsolved until to Date) and “Fermat’s Last Theorem: A New Proof of Theorem (Less than One and a Half Pages) and Its Generalization” 被引量:2
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作者 Demetrius Chr. Poulkas 《Advances in Pure Mathematics》 2021年第11期891-928,共38页
This article presents very original and relatively brief or very brief proofs about of two famous problems: 1) Are there any odd perfect numbers? and 2) “Fermat’s last theorem: A new proof of theorem and its general... This article presents very original and relatively brief or very brief proofs about of two famous problems: 1) Are there any odd perfect numbers? and 2) “Fermat’s last theorem: A new proof of theorem and its generalization”. They are achieved with elementary mathematics. This is why these proofs can be easily understood by any mathematician or anyone who knows basic mathematics. Note that, in both problems, proof by contradiction was used as a method of proof. The first of the two problems to date has not been resolved. Its proof is completely original and was not based on the work of other researchers. On the contrary, it was based on a simple observation that all natural divisors of a positive integer appear in pairs. The aim of the first work is to solve one of the unsolved, for many years, problems of the mathematics which belong to the field of number theory. I believe that if the present proof is recognized by the mathematical community, it may signal a different way of solving unsolved problems. For the second problem, it is very important the fact that it is generalized to an arbitrarily large number of variables. This generalization is essentially a new theorem in the field of the number theory. To the classical problem, two solutions are given, which are presented in the chronological order in which they were achieved. <em>Note that the second solution is very short and does not exceed one and a half pages</em>. This leads me to believe that Fermat, as a great mathematician was not lying and that he had probably solved the problem, as he stated in his historic its letter, with a correspondingly brief solution. <em>To win the bet on the question of whether Fermat was telling truth or lying, go immediately to the end of this article before the General Conclusions.</em> 展开更多
关键词 Perfect numbers Odd Perfect numbers Fermat’s Last Theorem Generalization of the Fermat’s Last Theorem Prime number Problems Millennium Problems
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The Theoretical Significance and Reality of Imaginary Number
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作者 Wenbing Wu Xiaojian Yuan 《Natural Science》 2023年第11期285-288,共4页
It is a fact that imaginary numbers do not have practical significance. But the role of imaginary numbers is very broad and enormous, due to the existence of Euler’s formula. Due to Euler’s formula, imaginary number... It is a fact that imaginary numbers do not have practical significance. But the role of imaginary numbers is very broad and enormous, due to the existence of Euler’s formula. Due to Euler’s formula, imaginary numbers have been applied in many theoretical theories. One of the biggest functions of imaginary numbers is to represent changes in phase, which is indispensable in signal analysis theory. The imaginary numbers in quantum mechanics pose a greater mystery: do the imaginary numbers really exist? This question still needs further scientific development to be answered. 展开更多
关键词 Imaginary number Euler’s Formula PHAsE Quantum Mechanics
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Representation of an Integer by a Quadratic Form through the Cornacchia Algorithm
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作者 Moumouni Djassibo Woba 《Applied Mathematics》 2024年第9期614-629,共16页
Cornachia’s algorithm can be adapted to the case of the equation x2+dy2=nand even to the case of ax2+bxy+cy2=n. For the sake of completeness, we have given modalities without proofs (the proof in the case of the equa... Cornachia’s algorithm can be adapted to the case of the equation x2+dy2=nand even to the case of ax2+bxy+cy2=n. For the sake of completeness, we have given modalities without proofs (the proof in the case of the equation x2+y2=n). Starting from a quadratic form with two variables f(x,y)=ax2+bxy+cy2and n an integer. We have shown that a primitive positive solution (u,v)of the equation f(x,y)=nis admissible if it is obtained in the following way: we take α modulo n such that f(α,1)≡0modn, u is the first of the remainders of Euclid’s algorithm associated with n and α that is less than 4cn/| D |) (possibly α itself) and the equation f(x,y)=n. has an integer solution u in y. At the end of our work, it also appears that the Cornacchia algorithm is good for the form n=ax2+bxy+cy2if all the primitive positive integer solutions of the equation f(x,y)=nare admissible, i.e. computable by the algorithmic process. 展开更多
关键词 Quadratic Form Cornacchia Algorithm Associated Polynomials Euclid’s Algorithm Prime number
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Small Modular Solutions to Fermat’s Last Theorem
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作者 Thomas Beatty 《Advances in Pure Mathematics》 2024年第10期797-805,共9页
The proof by Andrew Wiles of Fermat’s Last Theorem in 1995 resolved the existence question for non-trivial solutions in integers x,y,zto the equation xn+yn=znfor n>2. There are none. Surprisingly, there are infini... The proof by Andrew Wiles of Fermat’s Last Theorem in 1995 resolved the existence question for non-trivial solutions in integers x,y,zto the equation xn+yn=znfor n>2. There are none. Surprisingly, there are infinitely many solutions if the problem is recast in terms of modular arithmetic. Over a hundred years ago Issai Schur was able to show that for any n there is always a sufficiently large prime p0such that for all primes p≥p0the congruence xn+yn≡zn(modp)has a non-trivial solution. Schur’s argument wasnon-constructive, and there is no systematic method available at present to construct specific examples for small primes. We offer a simple method for constructing all possible solutions to a large class of congruences of this type. 展开更多
关键词 Fermat’s Last Theorem Modular Arithmetic CONGRUENCEs Prime numbers Primitive Roots Indices Ramsey Theory schur’s Lemma in Ramsey Theory
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Non-Darcy Flow in Molding Sands
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作者 Miguel A. Barron-Meza Joan Reyes-Miranda Daniel Flores-Sanchez 《Open Journal of Applied Sciences》 2024年第4期976-982,共7页
Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this ... Darcy’s law is widely used to describe the flow in porous media in which there is a linear relationship between fluid velocity and pressure gradient. However, it has been found that for high numbers of Reynolds this law ceases to be valid. In this work, the Ergun equation is employed to consider the non-linearity of air velocity with the pressure gradient in casting sands. The contribution of non-linearity to the total flow in terms of a variable defined as a non-Darcy flow fraction is numerically quantified. In addition, the influence of the shape factor of the sand grains on the non-linear flow fraction is analyzed. It is found that for values of the Reynolds number less or equal than 1, the contribution of non-linearity for spherical particles is around 1.15%. 展开更多
关键词 Darcy’s Law Molding sands Non-Darcy Flow Reynolds number shape Factor
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Reciprocity Relation between Alternative Gravity Formulas
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作者 Hans Hermann Otto 《Journal of Applied Mathematics and Physics》 2024年第4期1432-1440,共9页
We compare Newton’s force law of universal gravitation with a corrected simple approach based on Bhandari’s recently presented work, where the gravitation constant G is maintained. A reciprocity relation exists betw... We compare Newton’s force law of universal gravitation with a corrected simple approach based on Bhandari’s recently presented work, where the gravitation constant G is maintained. A reciprocity relation exists between both alternative gravity formulas with respect to the distances between mass centers. We conclude a one-to-one mapping of the two gravitational formulas. We don’t need Einstein’s construct of spacetime bending by matter. 展开更多
关键词 Gravity Formulas Reciprocity Distance Relation NEWTON EINsTEIN Bhandari Higgs Field Dirac’s Large number
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数论中的Wilson定理通过群论中的Cauchy定理的证明
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作者 张海诚 《高等数学研究》 2024年第5期93-93,F0003,共2页
本文利用近世代数课程中有限群的Cauchy定理证明数论课程里的Wilson定理.
关键词 数论 WILsON定理 群论 CAUCHY定理
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雷诺数和侧风对S型垂直轴风力机气动特性的影响
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作者 朱洋 左行 +1 位作者 朱建勇 赵秀勇 《风机技术》 2024年第1期69-76,共8页
相较于工作在郊外良好风场的大型风力机,小型风力机易受城市风环境如低风速、高湍流度以及时变风速风向的影响。采用数值模拟手段研究了雷诺数和来流倾角对小型S型垂直轴风力机气动性能的影响。研究结果表明:S型风力机的气动性能对雷诺... 相较于工作在郊外良好风场的大型风力机,小型风力机易受城市风环境如低风速、高湍流度以及时变风速风向的影响。采用数值模拟手段研究了雷诺数和来流倾角对小型S型垂直轴风力机气动性能的影响。研究结果表明:S型风力机的气动性能对雷诺数不敏感,功率系数几乎不随雷诺数变化;侧风导致S型风力机的气动性能变差,静扭矩系数和功率系数降低,并且随着侧风来流倾角的增大,气动性能越差,侧风影响的流动机理一方面是来流倾角降低了水平速度分量,另一个方面是竖直速度分量减小了前进叶片的压力差,增加回转叶片的压力差,进一步加剧了气动性能的恶化。 展开更多
关键词 风能 s型垂直轴风力机 雷诺数 来流倾角 数值模拟
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Shift, the Law of the Invention of Zero
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作者 Emmanuel Cadier Anaxhaoza 《Advances in Pure Mathematics》 2023年第5期237-249,共13页
After posing the axiom of linear algebra, the author develops how this allows the calculation of arbitrary base powers, which provides an instantaneous calculation of powers in a particular base such as base ten;first... After posing the axiom of linear algebra, the author develops how this allows the calculation of arbitrary base powers, which provides an instantaneous calculation of powers in a particular base such as base ten;first of all by developing the any base calculation of these powers, then by calculating triangles following the example of the “arithmetical” triangle of Pascal and showing how the formula of the binomial of Newton is driving the construction. The author also develops the consequences of the axiom of linear algebra for the decimal writing of numbers and the result that this provides for the calculation of infinite sums of the inverse of integers to successive powers. Then the implications of these new forms of calculation on calculator technologies, with in particular the storage of triangles which calculate powers in any base and the use of a multiplication table in a very large canonical base are discussed. 展开更多
关键词 AXIOM Axiom of Linear Algebra {ALA} Any Base Calculation ABC Theory number’s origin number Theory Newton’s Binomial Formula Pascal’s Triangle Base Z Canonical Bases Calculator Revolution Infinite sums of Inverse of Integer to the successive Powers Information Completion Theory Cipher Factorizations That Are numbers Infinite numbers That Are Infinite sums
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Origin and Distribution of Hydrogen Sulfide in Oil-Bearing Basins,China 被引量:9
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作者 ZHU Guangyou ZHANG Shuichang LIANG Yingbo 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2009年第6期1188-1201,共14页
The concentration of hydrogen sulfide gas (H2S) varies greatly in the oil-bearing basins of China, from zero to 90%. At present, oil and gas reservoirs with high H2S concentration have been discovered in three basin... The concentration of hydrogen sulfide gas (H2S) varies greatly in the oil-bearing basins of China, from zero to 90%. At present, oil and gas reservoirs with high H2S concentration have been discovered in three basins, viz. the Bohai Bay Basin, Sichuan Basin and the Tarim Basin, whereas natural gas with low H2S concentration has been found in the Ordos Basin, the Songliao Basin and the Junggar Basin. Studies suggest that in China H2S origin types are very complex. In the carbonate reservoir of the Sichuan Basin, the Ordos Basin and the Tarim Basin, as well as the carbonatedominated reservoir in the Luojia area of the Jiyang depression in the Bohai Bay Basin, Wumaying areas of the Huanghua depression, and Zhaolanzhuang areas of the Jizhong depression, the H2S is of Thermochemical Sulfate Reduction (TSR) origin. The H2S is of Bacterial Sulphate Reduction (BSR) origin deduced from the waterflooding operation in the Changheng Oilfield (placanticline oil fields) in the Songliao Basin. H2S originates from thermal decomposition of sulfur-bearing crude oil in the heavy oil area in the Junggar Basin and in the Liaohe heavy oil steam pilot area in the western depression of the Bohai Bay Basin. The origin types are most complex, including TSR and thermal decomposition of sulfcompounds among other combinations of causes. Various methods have been tried to identify the origin mechanism and to predict the distribution of H2S. The origin identification methods for H2S mainly comprise sulfur and carbon isotopes, reservoir petrology, particular biomarkers, and petroleum geology integrated technologies; using a combination of these applications can allow the accurate identification of the origins of H2S. The prediction technologies for primary and secondary origin of H2S have been set up separately. 展开更多
关键词 H2s TsR BsR DIsTRIBUTION origin mechanism oil-bearing basins
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The role of bone marrow-derived cells in the origin of liver cancer revealed by single-cell sequencing 被引量:4
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作者 Lu Chen Xianfu Yi +10 位作者 Piao Guo Hua Guo Ziye Chen Chunyu Hou Lisha Qi Yongrong Wang Chengwen Li Peng Liu Yucun Liu Yuanfu Xu Ning Zhang 《Cancer Biology & Medicine》 SCIE CAS CSCD 2020年第1期142-153,共12页
Objective:Epithelial cancers often originate from progenitor cells,while the origin of hepatocellular carcinoma(HCC)is still controversial.HCC,one of the deadliest cancers,is closely linked with liver injuries and chr... Objective:Epithelial cancers often originate from progenitor cells,while the origin of hepatocellular carcinoma(HCC)is still controversial.HCC,one of the deadliest cancers,is closely linked with liver injuries and chronic inflammation,which trigger massive infiltration of bone marrow-derived cells(BMDCs)during liver repair.Methods:To address the possible roles of BMDCs in HCC origination,we established a diethylnitrosamine(DEN)-induced HCC model in bone marrow transplanted mice.Immunohistochemistry and frozen tissue immunofluorescence were used to verify DENinduced HCC in the pathology of the disease.The cellular origin of DEN-induced HCC was further studied by single cell sequencing,single-cell nested PCR,and immunofluorescence-fluorescence in situ hybridization.Results:Studies by using single cell sequencing and biochemical analysis revealed that HCC cells in these mice were coming from donor mice BMDCs,and not from recipient mice.Furthermore,the copy numbers of mouse orthologs of several HCC-related genes previously reported in human HCC were also altered in our mouse model.DEN-induced HCCs exhibited a similar histological phenotype and genomic profile as human HCCs.Conclusions:These results suggested that BMDCs are an important origin of HCC,which provide important clues to HCC prevention,detection,and treatments. 展开更多
关键词 Hepatocellular carcinoma bone marrow-derived cells(BMDCs) originATION genome sequencing copy number alteration
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Identification of portal vein tumor thrombus with an independent clonal origin in hepatocellular carcinoma via multi-omics data analysis 被引量:1
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作者 Shupeng Liu Zaixin Zhou +5 位作者 Yin Jia Jie Xue Zhiyong Liu Kai Cheng Shuqun Cheng Shanrong Liu 《Cancer Biology & Medicine》 SCIE CAS CSCD 2019年第1期147-156,共10页
Objective: Multiple mechanisms underlying the development of portal vein tumor thrombus(PVTT) in hepatocellular carcinoma(HCC) have been reported recently. However, the origins of PVTT remain unknown. Increasing multi... Objective: Multiple mechanisms underlying the development of portal vein tumor thrombus(PVTT) in hepatocellular carcinoma(HCC) have been reported recently. However, the origins of PVTT remain unknown. Increasing multi-omics data on PVTTs in HCCs have made it possible to investigate whether PVTTs originate from the corresponding primary tumors(Ts).Methods: The clonal relationship between PVTTs and their corresponding primary Ts was investigated using datasets deposited in public databases. One DNA copy number variations dataset and three gene expression datasets were downloaded for the analyses.Clonality analysis was performed to investigate the clonal relationship between PVTTs and Ts from an individual patient.Differential gene expression analysis was applied to investigate the gene expression profiles of PVTTs and Ts.Results: One out of 19 PVTTs had no clonal relationship with its corresponding T, whereas the others did. The PVTTs with independent clonal origin showed different gene expression and enrichment in biological processes from the primary Ts. Based on the unique gene expression profiles, a gene signature including 24 genes was used to identify pairs of PVTTs and primary Ts without any clonal relationship. Validation in three datasets showed that these types of pairs of PVTTs and Ts can be identified by the 24-gene signature.Conclusions: Our findings show a direct evidence for PVTT origin and consolidate the heterogeneity of PVTTs observed in clinic.The results suggest that PVTT investigation at a molecular level is clinically necessary for diagnosis and treatment. 展开更多
关键词 HEPATOCELLULAR carcinoma portal VEIN tumor THROMBUs CLONAL origin COPY number variation bioinformatics
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Strong Law of Large Numbers and Complete Convergence for Sequences of -Mixing Random Variables 被引量:3
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作者 GAN Shixin CHEN Pingyan QIU Dehua 《Wuhan University Journal of Natural Sciences》 CAS 2007年第2期211-217,共7页
We give some theorems of strong law of large numbers and complete convergence for sequences of φ-mixing random variables. In particular, Wittmann's strong law of large numbers and Teicher's strong law of large nnum... We give some theorems of strong law of large numbers and complete convergence for sequences of φ-mixing random variables. In particular, Wittmann's strong law of large numbers and Teicher's strong law of large nnumbers for independent random variables are generalized to the case of φ -minxing random variables. 展开更多
关键词 strong law of large numbers complete convergence φ-mixing random variable sequence Wittmann's strong law oflarge numbers Teicher's strong law of large numbers
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Anomalous origin of left pulmonary artery branch from the aorta with Fallot's tetralogy:one case report 被引量:4
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作者 Cheng Wei Xiao Yingbin Zhong Qianjin Wen Renguo 《Journal of Medical Colleges of PLA(China)》 CAS 2008年第1期55-58,共4页
We report the case of a ten-year-old boy who had often presented with respiratory distress since born. Chest X-ray showed an enlarged right ventricle. Echocardiography demonstrated characteristic features of Fallot's... We report the case of a ten-year-old boy who had often presented with respiratory distress since born. Chest X-ray showed an enlarged right ventricle. Echocardiography demonstrated characteristic features of Fallot's tetralogy and the left pulmonary artery could not be visualized. However, cardiac catheterization disclosed that the left pulmonary artery had an anomalous origin in the ascending aorta. The patient underwent total surgical correction of the defects. Nine days later, he was discharged. We present the results of a literature review of the incidence, physiopathological, clinical, diagnostic, and surgical characteristics of this rare disease. 展开更多
关键词 Cardiac surgery Fallot's tetralogy Anomalous origin Left pulmonary artery
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Some results on circular chromatic number of a graph
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作者 吴建专 林文松 《Journal of Southeast University(English Edition)》 EI CAS 2008年第2期253-256,共4页
For two integers k and d with (k, d) = 1 and k≥2d, let G^dk be the graph with vertex set {0,1,…k - 1 } in which ij is an edge if and only if d≤| i -j I|≤k - d. The circular chromatic number χc(G) of a graph... For two integers k and d with (k, d) = 1 and k≥2d, let G^dk be the graph with vertex set {0,1,…k - 1 } in which ij is an edge if and only if d≤| i -j I|≤k - d. The circular chromatic number χc(G) of a graph G is the minimum of k/d for which G admits a homomorphism to G^dk. The relationship between χc( G- v) and χc (G)is investigated. In particular, the circular chromatic number of G^dk - v for any vertex v is determined. Some graphs withx χc(G - v) =χc(G) - 1 for any vertex v and with certain properties are presented. Some lower bounds for the circular chromatic number of a graph are studied, and a necessary and sufficient condition under which the circular chromatic number of a graph attains the lower bound χ- 1 + 1/α is proved, where χ is the chromatic number of G and a is its independence number. 展开更多
关键词 (k d)-coloring r-circular-coloring circular chromatic number Mycielski' s graph
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