Cesar Hernandez - Academia.edu (original) (raw)

Papers by Cesar Hernandez

Mechanism and Machine Theory, 2004

This article presents an integrated methodology for the determination of the workspace and the si... more This article presents an integrated methodology for the determination of the workspace and the singularity distribution for the 5R spherical, symmetric manipulator. In the first instance, the branching problem of the manipulator was considered and its solution was used to locate positions on a sphere that can be attained by the end effector. Moreover, it was found that the bounds on the workspace depend on the relative position existing between two major circles and two minor circles, which were geometrically determined in terms of the manipulatorÕs link lengths. Second, singular configurations were defined and singularity curves were generated. Thus, it was possible to obtain an integrated characterization scheme for the workspace and singularity distribution, by analyzing the relative position of the major and minor circles. As a result, 14 different characteristic shapes of the manipulatorÕs workspace and their related singularity curves were obtained. This should be a key issue in the context of manipulatorÕs design and trajectory design.

Transplantation, 1993

Recent studies suggest that graft microvascular endothelia may play an important role in the regu... more Recent studies suggest that graft microvascular endothelia may play an important role in the regulation of rejection. Alloantigen-dependent changes in microvascular endothelial phenotype may be associated with differences in infiltrate function in allografts vs. isografts, as reflected in alloantigen-specific CTL accumulation and cytokine production. To correlate cytokine production with differences in microvascular endothelial phenotype during allograft inflammation, we used PCR to identify cytokine mRNAs isolated from pooled cardiac isografts and allografts on days 1, 3, and 5 after transplantation. Graft microvascular endothelia express an inflamed phenotype associated with wound healing and the repair of tissue damage due to mechanical trauma, ischemia, and/or reperfusion injury--i.e., high levels of ICAM-1 expression and MECA-32 mAb reactivity. By day 1 in both isografts and allografts, mRNAs for the cytokines IL1 alpha, IL6, TNF, LT, and TGF beta are upregulated or induced. By the third day in cardiac allografts, an antigen-dependent endothelial phenotype is expressed, characterized by the presence of cell surface VCAM-1. Concomitantly, mRNAs for the lymphokines IL2 and IFN gamma are detected, followed by IL4 mRNA by day 5. The expression of VCAM-1 by allograft endothelia may influence the inflammatory process, by physically recruiting specific T cell subpopulations into the response and/or by delivering additional signals to the infiltrating cells. Eventually, these and other regulatory events occurring at these early times initiate a process that later results in alloreactive tissue destruction.

The security level of the EPC Class-1 Generation-2 RFID standard is very low, as shown in previou... more The security level of the EPC Class-1 Generation-2 RFID standard is very low, as shown in previous works such as . In particular, the security of the access and kill passwords of an RFID tag is almost non-existent. A first initiative by Konidala and Kim [5] tried to solve these problems by proposing a tag-reader mutual authentication scheme (TRMA) to protect the tag access password. However, Lim and Li showed how a passive attacker can recover the access password of the tag [6]. Recently, Konidala and Kim proposed a new version of the TRMA scheme (TRMA + ) in which the tag access and kill passwords are used for authentication . In this paper, we show that this new version still contains serious security flaws. The 16 least significant bits of the access password can be obtained with probability 2 −2 , and the 16 most significant bits with a probability higher than 2 −5 . Finally, we show how an attacker can recover the entire kill password with probability 2 −2 within 4 eavesdropped sessions in the case of a passive attack, or just 2 consecutive sessions under an active attack.

Rheumatic Disease Clinics of North America, 1998

Chaos Solitons & Fractals, 2008

In this paper, an analysis for chaos synchronization under nonvanishing perturbations is presente... more In this paper, an analysis for chaos synchronization under nonvanishing perturbations is presented. In particular, we use model-matching approach from nonlinear control theory for output synchronization of identical and nonidentical chaotic systems under nonvanishing perturbations in a master-slave configuration. We show that the proposed approach is indeed suitable to synchronize a class of perturbed slaves with a chaotic master system; that is the synchronization error trajectories remain bounded if the perturbations satisfy some conditions. In order to illustrate this robustness synchronization property, we present two cases of study: (i) for identical systems, a pair of coupled Rö ssler systems, the first like a master and the other like a perturbed slave, and (ii) for nonidentical systems, a Chua's circuit driving a Rö ssler/slave system with a perturbed control law, in both cases a quantitative analysis on the perturbation is included.

Anaerobe, 2006

The wood-boring beetle Anoplophora chinensis Forster, native to China, has recently spread to Nor... more The wood-boring beetle Anoplophora chinensis Forster, native to China, has recently spread to North America and Europe causing serious damage to ornamental and forest trees. The gut microbial community associated with these xylophagous beetles is of interest for potential biotechnological applications in lignocellulose degradation and development of pest-control measures. In this study the gut bacterial community of larvae and adults of A. chinensis, collected from different host trees in North Italy, was investigated by both culture and culture-independent methods. Larvae and adults harboured a moderately diverse bacterial community, dominated by Proteobacteria, Actinobacteria, and Firmicutes. The gammaproteobacterial family Enterobacteriaceae (genera Gibbsiella, Enterobacter, Raoultella, and Klebsiella) was the best represented. The abundance of such bacteria in the insect gut is likely due to the various metabolic abilities of Enterobacteriaceae, including fermentation of carbohydrates derived from lignocellulose degradation and contribution to nitrogen intake by nitrogen-fixing activity. In addition, bacteria previously shown to have some lignocellulose-degrading activity were detected at a relatively low level in the gut. These bacteria possibly act synergistically with endogenous and fungal enzymes in lignocellulose breakdown. The detection of actinobacterial symbionts could be explained by a possible role in the detoxification of secondary plant metabolites and/or protection against pathogens.

Computer Standards & Interfaces, 2009

RFID is a relatively heterogenous radio technology, where it is necessary to put an extra effort ... more RFID is a relatively heterogenous radio technology, where it is necessary to put an extra effort on security and privacy-related issues. As early as 2004, some authors suggested the use of a PRNG for increasing security. This was later questioned because many thought a PRNG implementation may go well beyond the very limited computational capabilities of low-cost RFID tags. However, its use has been ratified by EPCGlobal (EPC Class-1 Generation-2) and ISO (ISO/IEC 18000-6C). This motivates our proposal of a new PRNG, named LAMED, which is compliant with the standards and successfully passes several batteries of very demanding randomness tests (ENT, DIEHARD, NIST, and SEXTON). A study of its hardware complexity shows that LAMED can be implemented with slightly less than 1.6 K gates, and that pseudorandom numbers can be generated each 1.8 ms. So we can affirm this is a realist proposal both conforming with the EPC-G1C2 standard, and suitable for low-cost RFID tags.

Journal of Clinical Microbiology, 2003

RFID tags are devices of very limited computational capabilities, which only have 250-3K logic ga... more RFID tags are devices of very limited computational capabilities, which only have 250-3K logic gates that can be devoted to security-related tasks. Many proposals have recently appeared, but all of them are based on RFID tags using classical cryptographic primitives such as PRNGs, hash functions, block ciphers, etc. We believe this assumption to be fairly unrealistic, as classical cryptographic constructions lie well beyond the computational reach of very low-cost RFID tags. A new approach is necessary to tackle this problem, so we propose an extremely efficient lightweight mutual-authentication protocol that offers an adequate security level for certain applications and can be implemented even in the most limited low-cost RFID tags, as it only needs around 150 gates.

Journal of Information Science and Engineering

Low-cost Radio Frequency Identification (RFID) tags affixed to consumer items as smart labels are... more Low-cost Radio Frequency Identification (RFID) tags affixed to consumer items as smart labels are emerging as one of the most pervasive computing technologies in history. This presents a number of advantages, but also opens a huge number of security problems that need to be addressed before its successful deployment. Many proposals have recently appeared, but all of them are based on RFID tags using classical cryptographic primitives such as Pseudorandom Number Generators (PRNGs), hash functions, or block ciphers. We believe this assumption to be fairly unrealistic, as classical cryptographic constructions lie well beyond the computational reach of very low-cost RFID tags. A new approach is necessary to tackle the problem, so we propose a minimalist lightweight mutual authentication protocol for low-cost RFID tags that offers an adequate security level for certain applications, which could be implemented even in the most limited low-cost tags as it only needs around 300 gates.

RFID technology is a ubiquitous technology, and seems destined to become more a more ubiquitous. ... more RFID technology is a ubiquitous technology, and seems destined to become more a more ubiquitous. Traditional cryptographic primitives are not supported on low-cost RFID tags since, at most, 4K gates can be devoted to security-related tasks. Despite this, there are a vast number of proposals based on the use of classical hash functions, an assumption that is not realistic (at least at the present time). Furthermore, none of the published authentication protocols are resistant to active attacks. We try to address these two issues in this work by designing a new authentication protocol, secure against passive and active attacks, inspired by Shieh et al.’s protocol for smart-cards, but adapted to RFID systems. The original Shieh et al.’s scheme is considered one of the most secure an efficient protocols in the smart-card field. Because in this protocol tags should support a hash-function on-board, a new lightweight hash function, named Tav-128, is also proposed. A preliminary security analysis is shown, as well as a study on its hardware complexity, which concludes that its implementation is possible with around 2.6K gates.

Arthritis and Rheumatism, 1997

Objective. To describe the patterns of clinical presentation in a series of 407 patients with uve... more Objective. To describe the patterns of clinical presentation in a series of 407 patients with uveitis and to establish the relationship between these patterns and the final diagnosis.Methods. Patients were referred to the Uveitis Clinic of a tertiary hospital from January 1992 to January 1996. All patients received a complete ophthalmologic examination, and a general clinical history was obtained. The current International Uveitis Study Group classification system was used for anatomic classification. To establish the final diagnosis of the most common entities causing uveitis, current diagnostic criteria were used. A discriminant analysis, with diagnostic grouping as the outcome variable and the clinical presentation features as discriminating variables, was performed.Results. With our classification system, 66.5% of the cases could be correctly classified according to the clinical pattern and morphologic findings. By diagnostic groups, discriminant analysis showed that 75% of patients with Behçet's disease, 77.1% of those with spondylarthropathy (including inflammatory bowel disease), 33.3% of those with sarcoidosis, 97.9% of those with toxoplasmosis, 85.7% of those with Vogt-Koyanagi-Harada syndrome, 100% of those with herpes, and 50.4% of those with idiopathic uveitis were correctly classified. In the miscellaneous group, which included disease entities with fewer than 5 cases, 42.9% were correctly classified.Conclusion. Rheumatologic evaluation of the patient with uveitis can be more cost-effective if the referring ophthalmologist follows the classification system described herein, allowing a tailored approach in which only specific and necessary diagnostic tests are used.

Mechanism and Machine Theory, 2000

In this paper, a broadly applicable approach for numerically obtaining the workspace and the sing... more In this paper, a broadly applicable approach for numerically obtaining the workspace and the singularity curves of a planar RRRRR-type manipulator is presented. The workspace generation is formulated as a direct kinematic problem involving only two branches which are mathematically de®ned and related with the manipulator's assembly con®gurations. For solving that problem, the analytical solution of two simple quadratic equations is found. A simple existence criterion is also obtained to detect the set of points forming the manipulator's workspace. On the other hand, the singularity curves are composed of sets of singular points. In order to obtain the singular points, the properties of the Jacobian matrix are used. The complete method has been implemented and tested, as illustrated with examples for dierent geometrical properties of the manipulator. For each of these examples, the corresponding singularity curves are graphically generated to obtain the practical manipulator's workspace. This feature is a very powerful design tool which is indispensable in visualizing and analyzing the kinematic working capability of the manipulator. 7

Fems Microbiology Letters, 2004

A lysine aminopeptidase was purified from the yeast Kluyveromyces marxianus. This enzyme was puri... more A lysine aminopeptidase was purified from the yeast Kluyveromyces marxianus. This enzyme was purified 100-fold from a soluble extract obtained at 100,000g. The purification procedure consisted in fractionated precipitation with ammonium sulfate and five chromatography steps. The native enzyme had a molecular mass of 46 kDa assessed through gel filtration. This aminopeptidase depicted an optimal pH of 7.0 and was stable at a pH range of 4-8, its optimal temperature was 45°C and the enzyme became unstable at temperatures above 55°C. The isoelectric point of the purified enzyme was 4.4. Michaelis constant and V max for L L -lysinep-nitroanilide were 0.33 mM and 2.2 mM min À1 per milligram of protein, respectively. The enzyme was strongly inhibited by bestatin, o-phenanthroline and, to a lesser extent, by EDTA, suggesting that this enzyme is a metalloprotease. Our results suggest that the lysine aminopeptidase from Kluyveromyces marxianus might be of biotechnological relevance.

Arthritis and Rheumatism, 1994

Objective. To test the hypothesis that local proliferation contributes significantly to the hyper... more Objective. To test the hypothesis that local proliferation contributes significantly to the hyperplasia of rheumatoid synovium.Methods. Immunohistologic and chemical staining was used to identify 3 markers of cell proliferation: proliferating cell nuclear antigen, c-myc proto-oncogene, and nucleolar organizer regions. Synovium from 21 patients with rheumatoid arthritis, 34 with degenerative joint disease, and 7 with joint trauma was examined.Results. All 3 markers indicated substantial, active proliferation of synovial lining cells in synovium with hyperplasia. Proliferating cells showed type I procollagen immunoreactivity but were negative for CD68, a monocyte/macrophage marker. Proliferation was greater in rheumatoid arthritis than in the other conditions evaluated.Conclusion. In situ proliferation of fibroblast-like synoviocytes in the synovium lining contributes considerably to the increase in cell numbers in rheumatoid synovium.

Computer Standards & Interfaces, 2009

Journal of The American Association of Gynecologic Laparoscopists, 1998

Uterine tube prolapse into the vaginal vault is an uncommon complication after hysterectomy, and ... more Uterine tube prolapse into the vaginal vault is an uncommon complication after hysterectomy, and our 6 patients bring to 90 the number of cases reported in the literature. Symptoms consist almost exclusively of vaginal bloody discharge and/or leukorrhea, persistent pelvic pain, and dyspareunia. Surgical treatment must be individualized according to the patient's symptoms. In our series, sexually active women with pelvic pain and dyspareunia had the best outcome when a combined laparoscopic and vaginal approach was used.

American Journal of Obstetrics and Gynecology, 2002

The purpose of this study was to examine the roles of intrauterine infection, inflammation, and s... more The purpose of this study was to examine the roles of intrauterine infection, inflammation, and spontaneous labor on the expression of matrix metalloproteinase-9 in fetal membranes and amniotic fluid of late pregnant rhesus monkeys. Pregnant rhesus monkeys with timed gestations were chronically catheterized to allow serial sampling of amniotic fluid before and during experimentally induced intrauterine inflammation. Six animals received group B streptococci into the chorionic-decidual space, and 4 animals received intra-amniotic interleukin-1 beta infusions (10 microg). Three additional animals were serially sampled by amniocentesis through late pregnancy until spontaneous term labor. Amniotic fluid samples were examined by zymography for matrix metalloproteinase-9 and -2 and Western immunoblot for matrix metalloproteinase-9 and -2 and tissue inhibitors of metalloproteinase-1 and -2. Fetal membranes were obtained at cesarean delivery during labor (before rupture), formalin fixed, and embedded in paraffin for immunocytochemistry of matrix metalloproteinase-9 and in situ hybridization of matrix metalloproteinase-9 messenger RNA. Tissues from 2 additional animals were collected as age-matched non-labor controls. In amniotic fluid, the 92-kd latent matrix metalloproteinase-9 was detectable in late pregnancy and increased dramatically, followed by the appearance of the 83-kd active form before spontaneous term delivery. Amniotic fluid matrix metalloproteinase-2 levels (both latent and active forms) remained relatively constant throughout pregnancy and in labor. Both bacteria and interleukin-1 beta rapidly increased the signal of latent matrix metalloproteinase-9 without a consistent increase in the active form before the onset of labor. Chorionic-decidual inoculation of group B streptococci was followed by the expression of latent matrix metalloproteinase-9 before the appearance of group B streptococci in amniotic fluid or the onset of labor. Matrix metalloproteinase-2 increased to a new steady-state level or remained unchanged after group B streptococci inoculation or interleukin-1 beta infusion, respectively. Amniotic fluid tissue inhibitors of metalloproteinase-1 declined and tissue inhibitors of metalloproteinase-2 remained unchanged during early group B streptococci infection, after interleukin-1 beta infusion and on the day of spontaneous term labor. However, both tissue inhibitors of metalloproteinase-1 and -2 levels increased after preterm labor that was induced by group B streptococci. Immunocytochemistry localized matrix metalloproteinase-9 protein to amnion and chorion epithelial and mesenchymal cells and decidual stromal cells. Granular matrix metalloproteinase-9 staining was observed in the connective tissue layer of inflamed fetal membranes. In situ hybridization for messenger RNA confirmed the production of matrix metalloproteinase-9 by amnion and chorion. Bacterial- and interleukin-1 beta-induced preterm labor and spontaneous term labor are preceded and accompanied by progressive increases in amniotic fluid matrix metalloproteinase-9 (92 kd) in rhesus monkeys. Amniotic fluid matrix metalloproteinase-9 may serve as a clinical marker for the onset of both preterm and term labor.

Mechanism and Machine Theory, 2004

Transplantation, 1993

Rheumatic Disease Clinics of North America, 1998

Chaos Solitons & Fractals, 2008

Anaerobe, 2006

Computer Standards & Interfaces, 2009

Journal of Clinical Microbiology, 2003

Journal of Information Science and Engineering

Arthritis and Rheumatism, 1997

Mechanism and Machine Theory, 2000

Fems Microbiology Letters, 2004

Arthritis and Rheumatism, 1994

Computer Standards & Interfaces, 2009

Journal of The American Association of Gynecologic Laparoscopists, 1998

American Journal of Obstetrics and Gynecology, 2002