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Pseudo random oracle of Merkle-Damg?rd hash functions revisited

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Science China(Information Sciences) 2019年第3期 160-174页

作者： kamel AMMOUR Lei WANG Dawu GU School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University

Following the well-known random oracle Methodology, a cryptographic hash function is required to satisfy the property of pseudo-random oracle(PRO), that is indifferentiable from a random oracle. This paper revisits the PRO property of popular hash function modes purely from a theoretical point of *** Merkle-Damg?rd mode(sometimes referred to as Strengthened Merkle-Damg?rd) does not satisfy the PRO security due to the length-extension attack. To remedy it, a series of variants have been proposed with tweaks of either adopting a prefix-free padding or modifying the final primitive call. From these tweaks, we derive a common structural property named prefix-free computing. Indeed, all PRO-secure Merkle-Damg?rd variants published so far are prefix-free computing. Hence, an interesting question with respect to the nature of PRO security arises: is prefix-free computing a necessary condition for PRO-secure Merkle-Damg?rd hash function? This paper gives a negative answer. We investigate the difference between length-extension resistance and prefix-free computing, and find that length-extension resistance does not necessarily imply prefix-free computing. Consequently, we construct a dedicated Merkle-Damg?rd variant as a counterexample that is PRO-secure but not prefix-free computing.

关键词： Merkle-Damg?rd random oracle indifferentiability prefix free length extension attack

Effect of concrete buildings on the environmental neutron flux by using the reaction ^(197)Au (n,γ) ^(198)Au and extremely low level gamma ray spectroscopy

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Nuclear Science and Techniques 2004年第6期15卷 368-374页

作者： K. KOMURA N.K. AHMED A.H. EL-kamel A.M.M. YOUSEF Low Level Radioactivity Laboratory Kanazawa University Wake Tatsunokuchi Ishikawa 923-1224 JapanPhysics Department Faculty of Science South Valley University Kena EgyptPhysics Department Faculty of Science Assiut University Assiut EgyptPhysics Department Faculty of Science South Valley University Kena Egypt

The activation of gold by environmental neutrons through the reaction 197Au (n,γ) 198Au was used to study the effect of concrete buildings on the neutron flux, and to estimate the thermal neutron flux inside and outside these buildings. The results showed that three ceilings of thickness 34 g/cm2 decrease the fast neutrons to 26% from its original value. However, the same reinforced concrete decreases the slow neturon flux to only 62% of its original value. The thermal neutron flux at 283 m from the center of Training Reactor of Kinki University, was twice higher than the environmental neutron background.

关键词：金活性混凝土环境中子宇宙射线

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Variation of environmental neutron flux with altitude and depth of both water and soil

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Nuclear Science and Techniques 2004年第4期15卷 248-256页

作者： K.KOMURA N.K.AHMED A.H.EL-kamel A.M.M.YOUSEF Low Level Radioactivity Laboratory Kanazawa UniversityWake TatsunokuchiIshikawa 923-1224JapanPlrysics DepartmentFaculty of Science.South Valley UniversityKenaEgyptPhysics DepartmentFaculty of ScienceAssiut UniversityAssiutEgyptPhysics DepartmentFaculty of Science.South Valley UniversityKenaEgypt

Applying the extreme low-level γ-ray spectroscopic analysis the environmental neutron flux is measured using different moderator construction and environment through the reaction 197Au (n, γ) 198Au. The contribution of thermal and resonance neutrons is separated using the cadmium difference technique, while fast neutrons are measured by the paraffin moderator. The results of altitude dependence of the neutron flux are discussed. The thermal neutron flux near the surface of sea water is less than its value at 100 cm over ground near sea water, while the value over the surfaces of fresh water is higher than that near the surface of sea water. Also the thermal neutron flux at 5 cm soil depth increases, then decreases to its original value at 10 cm depth and still constant until 25 cm, then decreases rapidly to reach 27% of its original value at 60 cm depth. The soil compositions, corresponding neutron temperatures and effective absorption cross sections of earth are the most effective factors on the equilibrium region of thermal neutrons in the ground.

关键词：环境中子流金活化作用 γ射线光谱学环境放射学水土壤

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Correlation between corneal demarcation line depth in epithelium-off and trans-epithelium accelerated corneal cross linking and keratoconus progression

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International Journal of Ophthalmology(English edition) 2020年第6期13卷 907-912页

作者： Mahmoud Abdel-Radi Zeiad Eldaly Hazem Abdelmotaal Reham Abdelrahman Mohamed Sayed kamel Soliman Department of Ophthalmology Assiut UniversityAssiut 71516Egypt

AIM:To compare corneal demarcation line(DL)depth in both accelerated epithelium-off and trans-epithelium cross linking(CXL)using anterior segment optical coherence tomography(AS-OCT)and its relation to maximum keratometry(Kmax)progression in both ***:A prospective comparative interventional study where patients with mild to moderate keratoconus(KC)were classified into two groups:accelerated epitheliumoff and trans-epithelium CXL based on corneal *** of corneal DL depth was carried out after 3mo by *** readings were evaluated after one year follow up using the Scheimpflug imaging ***:Study included 74 eyes of 44 *** A underwent epithelium-off CXL(41 eyes),while Group B underwent trans-epithelium CXL(33 eyes).At 3mo follow up,mean corneal DL depth in Group A was 219.9±58.4μm while in Group B was 127.2±7.8μm(P0.05).In addition,no significant change in corneal pachymetry was found in both groups(meanchange at 1y:6.4±4.7 and-10.1±2.3μm in Groups A and B respectively).CONCLUSION:Despite a significantly deeper corneal DL depth created by accelerated epithelium-off CXL technique compared to accelerated trans-epithelium CXL,there is no significant impact on keratoconus progression.

关键词： anterior segment optical coherence tomography cross linking demarcation line keratoconus

Assessment of antifungal activity of herbal and conventional toothpastes against clinical isolates of Candida albicans

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Asian Pacific Journal of Tropical Biomedicine 2012年第5期2卷 375-379页

作者： Ghaleb Adwan Yousef Salameh kamel Adwan Ali Barakat Department of Biology and Biotechnology An-Najah N.University Statistics Department An-Najah N.University

Objective:To detect the anticandidal activity of nine toothpastes containing sodium fluoride, sodium monofluorophosphate and herbal extracts as an active ingredients against 45 oral and non oral Candida albicans(***) ***:The antifungal activity of these toothpaste formulations was determined using a standard agar well diffusion *** analysis was performed using a statistical package,SPSS windows version 15,by applying mean values using one-way ANOVA with post-hoc least square differences(LSD) method.A P value of less than 0.05 was considered ***:All toothpastes studied in our experiments were effective in inhibiting the growth of all *** *** highest anticandidal activity was obtained from toothpaste that containing both herbal extracts and sodium fluoride as active ingredients, while the lowest activity was obtained from toothpaste containing sodium monofluorophosphate as an active *** activity of Parodontax toothpaste showed a significant difference(P<0.001) against *** isolates compared to toothpastes containing sodium fluoride or herbal ***:In the present study,it has been demonstrated that toothpaste containing both herbal extracts and sodium fluoride as active ingredients are more effective in control of ***,while toothpaste that containing monofluorophosphate as an active ingredient is less effective against *** herbal toothpaste formulations studied in our experiments,appear to be equally effective as the fluoride dental formulations and it can be used as an alternative to conventional formulations for individuals who have an interest in naturally-based *** results may provide invaluable information for dental professionals.

关键词： Candida albicans Sodium fluoride Sodium monofluorophosphate Herbal toothpaste Conventional toothpaste Anticandidal activity Fluoride Oral cavity Herbel extract Plaque

The Multifractal Formalism for Measures, Review and Extension to Mixed Cases

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Analysis in Theory and Applications 2016年第4期32卷 303-332页

作者： Mohamed Menceur Anouar Ben Mabrouk kamel Betina Algerba and Number Theory Laboratory Faculty of Mathematics University of Sciences and Technology Houari Boumediene Computational Mathematics Laboratory Department of Mathematics Faculty of Sciences Department of Mathematics HIgher Institute of Applied Mathematics and Informatics Street of Assad Ibn Alfourat Kairouan University

The multifractal formalism for single measure is reviewed. Next, a mixed generalized multifractal formalism is introduced which extends the multifractal formalism of a single measure based on generalizations of the Hausdorff and packing measures to a vector of simultaneously many measures. Borel-Cantelli and Large deviations Theorems are extended to higher orders and thus applied for the validity of the new variant of the multifractal formalism for some special cases of multi-doubling type measures.

关键词： Hausdorff measures packing measures Hausdorff dimension packing dimension renyi dimension multifractal formalism vector valued measures mixed cases Holderian measures doubling measures Borel-Cantelli large deviations

Hepatitis C Virus RNA Strands Detection in Peripheral Blood Mononuclear Cells Legitimizes Virus Eradication in Negative Serum PCR Naive and Post-treatment Patients

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Journal of Clinical and Translational Hepatology 2017年第1期5卷 1-8页

作者： Mohamed Darwish Ahmed Abd Alla Mostafa kamel El Awady Tropical Medicine Department Faculty of MedicineAl-Azhar UniversityCairoEgypt Department of Microbial Biotechnology National Research CenterCairoEgypt

Background and Aims:Hepatitis C virus(HCV)hepatotropism is associated with intra-peripheral blood mononuclear cell(PBMC)infection that causes post-treatment relapse in RNA seronegative *** understanding of the association of non-viremic hepatic fibrosis with positive anti-HCV IgG antibodies and active hepatocellular damage might be increased by PBMCs screening for intracellular ***,the goals of this study included evaluation of PBMCs PCR for diagnosing HCV infection,addressing PBMCs plus serum real-time(SRT)PCR benefits over SRT-PCR alone,studying intraPBMCs distribution of RNA sense and antisense strands,and identifying treatment feasibility in solitary intracellular ***:Enzyme-linked immunosorbent assay,SRT-PCR and PBMCs PCR were used to evaluate HCV infection in 401 *** patients were classified into groups of negative controls(n=30),positive controls(n=63),non-viremia post-treatment(experienced;n=166)and na(i)ve(n=49)cases,and non-viremia positive PBMCs PCR na(i)ve(n=35)and experienced(n=58)***:The diagnosis of true positive and negative by PBMCs PCR and SRT-PCR had 100%and 96.7%compatibility *** PCR detected intracellular HCV infection in 49 out of 215 non-viremia patients;among them,na(i)ve cirrhotics had significantly higher number of intracellular infection than the na(i)ve non-cirrhotic(P<0.001)and experienced patients(P<0.0001).Antisense and sense strands were respectively recognized in na(i)ve and experienced cases(P=0.01218).Intracellular HCV strands were detected in 18.02%of experienced *** of intracellular RNA strands showed significant decline in experienced compared to na(i)ve patients(P<0.05).Conclusion:PBMCs PCR is a valid diagnostic test that can diagnose intracellular HCV when SRT-PCR is *** and sense strands are respectively recognized more often in na(i)ve and experienced *** expected overall relapsing rate in our cohort was 18.02%.Int

关键词： HCV PBMCs RNA Strands

Causes of gastrointestinal bleeding in children based on endoscopic evaluation at a tertiary care center in Bahrain

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World Journal of Gastrointestinal Endoscopy 2023年第4期15卷 297-308页

作者： Hasan M Isa Fatema A Alkharsi Hana A Ebrahim kamel J Walwil Jumana A Diab Nafelah M Alkowari Department of Pediatrics Salmaniya Medical ComplexManama 26671Bahrain Department of Pediatrics Arabian Gulf UniversityManama 26671Bahrain Department of Pediatrics Royal College of Surgeons in Ireland-Medical University of BahrainBusaiteen 15503Bahrain Department of Pediatrics King Hamad University HospitalMuharraq 24343Bahrain

BACKGROUND Gastrointestinal bleeding(GIB)is a serious health problem worldwide,particularly during *** can be an alarming sign of an underlying *** endoscopy(GIE)is a safe method for the diagnosis and treatment of GIB in most *** To determine the incidence,clinical presentation,and outcomes of GIB in children in Bahrain over the last two *** This was a retrospective cohort review of the medical records of children with GIB who underwent endoscopic procedures in the Pediatric Department at Salmaniya Medical Complex,Bahrain,between 1995 and *** data,clinical presentation,endoscopic findings,and clinical outcomes were *** was classified into upper(UGIB)and lower(LGIB)GIB according to the site of *** were compared with respect to patients’sex,age,and nationality using the Fisher’s exact,Pearson’sχ2,or the Mann-Whitney U *** A total of 250 patients were included in this *** median incidence was 2.6/100000 per year(interquartile range,1.4-3.7)with a significantly increasing trend over the last two decades (P < 0.0001). Most patients were males (n = 144, 57.6%). Themedian age at diagnosis was 9 years (5-11). Ninety-eight (39.2%) patients required upper GIEalone, 41 (16.4%) required colonoscopy alone, and 111 (44.4%) required both. LGIB was morefrequent (n = 151, 60.4%) than UGIB (n = 119, 47.6%). There were no significant differences in sex (P = 0.710), age (P = 0.185), or nationality (P = 0.525) between the two groups. Abnormalendoscopic findings were detected in 226 (90.4%) patients. The common cause of LGIB was inflammatorybowel disease (IBD) (n = 77, 30.8%). The common cause of UGIB was gastritis (n = 70, 28%).IBD and undetermined cause for bleeding were higher in the 10-18 years group (P = 0.026 and P =0.017, respectively). Intestinal nodular lymphoid hyperplasia, foreign body ingestion, andesophageal varices were more common in the 0-4 years group (P = 0.034, P < 0.0001

关键词： Pediatric Gastrointestinal bleeding Endoscopy Causes Outcome Bahrain

The Beneficial Effect of 3-Month-Induction Therapy with Corticosteroids and Mycophenolate Mofetil Followed by Maintenance Therapy with Yearly Rituximab Infusions as Sole Maintenance Therapy in Cryptogenic Chronic Hypersensitivity Pneumonitis

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International Journal of Clinical Medicine 2023年第8期11卷 338-346页

作者： kamel El-Reshaid Abdulmohsen Al-Bader Sana S. Almutairi Sayed H. M. Mohamad Department of Medicine Faculty of Medicine Kuwait University Kuwait City Kuwait Department of Otolaryngeology Farwania Hospital Ministry of Health Kuwait City Kuwait Department of Medicine Respiratory Unit Amiri Hospital Ministry of Health Kuwait City Kuwait Department of Radiology Al Salam Hospital Kuwait City Kuwait

Background: The available data on cryptogenic chronic hypersensitivity pneumonitis (ccHP) indicate an inherited predisposition to disease with triggering autoimmune phenomena. Hence, we evaluated prospectively the role of a new autoimmune regimen in treatment of its severe and progressive disease. Patients and Methods: A total of 9 patients were included in the study. They had criteria for ccHP viz. 1) clinical features of cryptogenic progressive restrictive lung disease, 2) high-resolution computed tomographic pulmonary abnormalities, and 3) bronchoalveolar lavage lymphocytosis (>30%). The regimen consisted of an initial induction phase of 3-month Solumedrol 1 g IV daily for 3 days followed by 1 month of Prednisone (P) 60 mg/day to tapered down to discontinuation by 3rd month. They also had received Mycophenolate mofetil (MMF) 1 g twice daily for 3 months. This stage was followed by a maintenance phase of yearly Rituximab infusions (1 g followed by 1 g 2 weeks later). Results: compared to their previous 6 months deterioration;all patients showed significant improvement in their forced vital volume, diffusion capacity for carbon monoxide, 6-minutes-walk after the induction phase (at 3 months) which improved further at 15 months with Rituximab therapy. Conclusion: After 3-month induction therapy with P and MMF;yearly R treatment is a safe, practical and effective long-term therapy for ccHP.

关键词： Hypersensitivity Pneumonitis Mycophenolate Mofetil Rituximab Spirometry HRCT BAL