Now showing items 25385-25404 of 39117

    • O'odham ki: The development of a theme residence and its effect on American Indian students

      Stauss, Joseph A.; Mason, Julia Marie, 1970- (The University of Arizona., 1994)
      American Indian students have historically been underrepresented in higher education. Graduation and persistence rates for American Indians are distressingly low. Increasing Indian student retention has become a priority on many campuses. At the University of Arizona, a wing within a residence hall was reserved for American Indian students as part of a recruitment and retention program. The purpose of this thesis was to describe and assess the history, development and implementation of the American Indian wing. All of the traditional predictors for academic success show that the residents of the wing were at risk for dropping out of college. All of the first year students who lived on the wing were enrolled in Spring 1994. Given this important indicator the wing was a success. The American Indian wing was the beginning of a retention program that encourages Indians to remain at college without compromising cultural values.
    • O'odham rhythms

      Hammond, Michael; Fitzgerald, Colleen Miriam, 1969- (The University of Arizona., 1997)
      Morphology and syllable weight have both been shown to affect stress patterns, but these effects are analyzed in different ways. The theoretical goal of this dissertation is to propose a Optimality Theoretic model to account for how morphology influences stress, and to do this in a way that parallels the influence of weight upon stress. Prince (1990) lays out the W scEIGHT- scTO-S scTRESS P scRINCIPLE, formalizing the principle by which heavy syllables attract stress in quantity-sensitive systems. I argue for the M scORPHEME- scTO-S scTRESS P scRINCIPLE, a constraint that forces morphemes to attract stress in morphological stress systems. The W scEIGHT- scTO-S scTRESS P scRINCIPLE has a counterpart, the S scTRESS- scTO-W scEIGHT P scRINCIPLE, which forces stressed syllables to be heavy. The counterpart of the M scORPHEME- scTO-S scTRESS P scRINCIPLE is the S scTRESS- scTO-M scORPHEME P scRINCIPLE, which forces stressed syllables to belong to morphemes. This accounts for systems where epenthetic vowels resist stress assignment.
    • O-glycopeptide analogues of enkephalin: FMOC-amino acid glycoside synthesis, solid-phase glycopeptide synthesis and optimizations, and pharmacology

      Polt, Robin L.; Mitchell, Scott Allan (The University of Arizona., 1999)
      The synthesis of a series of N-9-fluorenylmethoxycarbonyl (N-FMOC) protected amino acid glycosides is reported. These (1-2)-trans glycosides came directly from Koenigs-Knorr type glycosylations under Hanessian's silver triflate conditions, except for the synthesis of N-acetylgalactosamine FMOC amino acid in which silver perchlorate conditions were used to promote α-glycoside formation. The effect of D-amino acid aglycones was investigated under glucosylation conditions, and a yield dependence on amino protection was seen in the enantiomers of threonine. Due to this match vs. mismatch dichotomy, both O'Donnell Schiff bases and FMOC-amino aglycones were used in the subsequent glycosylation reactions. Glycosides were made using the monosaccharides xylose, mannose, glucose, galactose, N-acetylglucosamine, N-acetylgalactosamine, and disaccharides lactose [galactose-β-(1-4)-glucose], cellobiose [glucose-β-(1-4)-glucose] and melibiose [galactose-α-(1-6)-glucose]. All glycosides were converted to their respective FMOC-amino acid forms for direct use in solid-phase glycopeptide synthesis (SPGPS) using established methodology. A strategy into the synthesis of an FMOC-amino acid trisaccharide of Lewis ˣ (Leˣ) was also investigated in an effort to expand on the established glycoside methodology. Preliminary work with D-glucosamine and L-fucose is reported. Our synthetic rationale was based on retaining the peptide pharmacophore or message sequence constant as DCDCE (D-cys²ʼ⁵-enkephalin) with a serine-glycine tether, and making changes only in the environment of the amino-acid glycoside. Changes in amino acid, amino acid chirality, and in the sugar moiety itself would provide a stereochemical investigation into the requisite orientation and electronics for optimum blood-brain barrier (BBB) penetration, opiate receptor binding, and analgesia. Several glycopeptides were synthesized, and all were purified in both reduced and oxidized forms (if containing cysteine). A highly optimized glycopeptide synthetic strategy has been developed and will be presented and critiqued. Pharmacological analysis involving serum stability studies, BBB-penetration studies, GPI/MVD physicochemical studies and mu/delta-opiate receptor studies were completed on all glycopeptides. SAM-1095, the most potent of the glycopeptides synthesized, was resynthesized on a large scale, and this compound was assessed for in vivo pharmacology, along with the non-glycosylated version SAM-995. Preliminary results demonstrate an analgesic effect similar to that of the narcotic morphine. Assessment of all pharmacology will afford a platform for future SAR-based glycopeptide investigations.
    • O-okun Yoruba in Yoruba art historiography: History, problems and prospects

      Omari-Obayemi, Mikelle Smith; Ijagbemi, Bayo, 1963- (The University of Arizona., 1996)
      One of the most obtrusive features of Yoruba studies has been its clear pattern of regional preferences and biases in its scholarship. This pattern is reflected in the present concentration of studies on the southwest, the northwest, the central subgroups of Ife, Owo, Ijesha, Egba, Ijebu, Oyo, and Ilorin on one hand, and the paucity of works on the northeast and southeast subgroups of the O-okun Yoruba, the Igbomina, the Ikale and the Ilaje on the other. There is no other subgroup where this particularistic trend in Yoruba studies and especially, art historiography can better be observed than with the scholarly neglect of the O-okun peoples, the most northeasterly of the Yoruba subgroups. An important goal of this thesis is to foreground the multi-culturalistic tendencies among the Yoruba and underscore the necessity to provide comparable scholarly attention to neglected subgroups, the O-okun peoples in particular.

      Dueñez, Ricardo Luis, 1954- (The University of Arizona., 1987)
    • Oaths and imprecations in Chaucer's Canterbury tales

      Birdsall, Esther Katherine Schiefer, 1924- (The University of Arizona., 1950)
    • Obese Adolescent Females and Actual Behavioral Responses to a Mindful Eating Intervention

      Berg, Judith; Daly, Patricia; Berg, Judith; Moore, Ki; Archbold, Kristen (The University of Arizona., 2013)
      Background: Adolescent obesity has tripled over the last three decades and is associated with an 80 percent risk of adult obesity, hypertension, diabetes, hypercholesterolemia, and decreased life expectancy. Current adolescent obesity medical recommendations include bariatric surgery and appetite suppressants which lower BMI, but present serious health risks. Nutrition and exercise interventions promote health, however, meta-analysis reveal do not lower BMI. Mindful eating, a behavioral skill, reconnecting eating to satiety cues, and has potential as an anti-obesity intervention which lowers BMI, while promoting health. Study Aims: Aim 1: To determine the effect of a mindful eating intervention compared to usual diet and exercise information on BMI of obese female adolescents. Aim 2: To determine if the effect of a mindful eating intervention on BMI of obese female adolescents is sustained over time. Aim 3: To determine the feasibility of conducting a group mindful eating intervention over six weeks for obese adolescent girls in their school setting. Methods: Obesity was measured by Body Mass Index (BMI) = Weight in Pounds / Height in inches x Height in inches x 703. The sample included adolescent females aged 14-17 years with BMI>90th%. Participants were randomized to an intervention group receiving a 6 week mindful eating intervention and a comparison group receiving the usual care of nutrition and physical activity handouts. Participants' BMI was measured at baseline, immediately post intervention and at 4 week follow up assessing intervention effectiveness. Results: ANOVA results demonstrate a statistically significant difference in BMI between the experimental and comparison groups F(1,2)=22.24, p<.001. On average, the experimental group's BMI decreased 0.71, whereas the comparison group's BMI increased by 1.1 over the 6 week intervention. The experimental group's BMI continued to decline at the 4 week follow up. Attrition from the study was 38%, below the 45% set feasibility threshold. A group mindful eating intervention over six weeks for obese adolescent girls was effective in lowering BMI sustained over time is feasible. Teaching the behavioral skill of mindful eating holds great promise for combatting obesity in adolescents. Future study should include a school based intervention with a larger more diverse sample.

      Fuglevand, Andrew; Hassan, Yezan Haitham (The University of Arizona., 2018)
      Clinically relieving pain is a top priority in the fields of pharmacology, health sciences, medicine, and neuroscience. With a plethora of pain-related or pain-inflicting conditions and disorders, understanding how this sensory system’s circuitry functions is proving to be more and more valuable. This review looks shines light on the role that adipose tissue and obesity can have on nociception and focuses on the interest in studying the periaqueductal gray matter.
    • Obesity in a Southwest Native American tribe: Examination of prevalence, predictive factors, and health risks

      Gray, Norma (The University of Arizona., 1989)
      This research examined obesity in a Southwest Native American Tribe by utilizing data obtained from Indian Health Service regarding individuals who used their health clinics. Sixteen cohorts, ranging in age from 3 to 75 years, were studied across the four years of 1971, 1976, 1981, and 1986. This was an exploratory study designed to investigate four areas related to obesity in this Tribe: (1) Weight and height norms, (2) prevalence of obesity, (3) factors predictive of adolescent obesity, and (4) health risks associated with obesity. The results indicate that this population of Southwest Native Americans generally weigh more and are shorter than national norms, which results in significantly greater BMIs. Norms for weight, height, and Body Mass Index (BMI) were established for all categories during each of the data gathering years of 1971, 1976, 1981, and 1986. Prevalence of obesity based on weight and BMI was established for this time period, also. Predictive factors of adolescent obesity in this Tribe revealed several of children's prior weight variables to be significantly related to adolescent obesity. Whereas, variables related to the children's mothers tended to be nonsignificant. The results indicated two health problems are related to adult obesity in this population: diabetes and cardiovascular disorders. In addition, blood pressure was also related to obesity in that those who were obese tended to have higher systolic and diastolic blood pressures than the nonobese. Several childhood characteristics are seen as indicators that children may need preventive measures in order to reduce the chance of later obesity. Future research is discussed in terms of prospective studies which might provide more information about obesity in this Tribe.
    • Obfuscation of Transmission Fingerprints for Secure Wireless Communications

      Krunz, Marwan; Rahbari, Hanif; Lazos, Loukas; Li, Ming; Krunz, Marwan (The University of Arizona., 2016)
      Our world of people and objects is on the verge of transforming to a world of highly-interconnected wireless devices. Incredible advances in wireless communications, hardware design, and power storage have facilitated hasty spread of wireless technologies in human life. In this new world, individuals are often identified and reached via one or multiple wireless devices that they always carry (e.g., smartphones, smart wearable, implantable medical devices, etc.), and their biometrics identities are replaced by their digital fingerprints. In near future, vehicles will be controlled and monitored via wireless monitoring systems and various physical objects (e.g., home appliance and retail store items) will be connected to the Internet. The list of these changes goes on. Unfortunately, as different aspects of our lives are being immerged in and dependent to wireless devices and services, we will become more vulnerable to wireless service/connection interruptions due to adversarial behavior and our privacy will become more potent to be exposed to adversaries. An adversary can learn the procedures of a wireless system and analyze its stages, and accordingly, launch various attacks against the operations of the system or the privacy of the people. Existing data confidentiality and integrity services (e.g., advanced encryption algorithms) have been able to prevent the leakage of users' messages. However, in wireless networks, even when upper-layer payloads are encrypted, the users' privacy and the operation of a wireless network can be threatened by the leakage of transmission attributes at the physical (PHY) layer. Examples of these attributes are payload size, frequency offset (FO), modulation scheme, and the transmission rate. These attributes can be exploited by an adversary to launch passive or active attacks. A passive attacker may learn about the interests, sexual orientation, political views, and patentable ideas of the user through analyzing these features, whereas an active attacker exploits captured attributes to launch selective packet jamming/dropping and disrupt wireless services. These call for novel privacy preserving techniques beyond encryption. In this dissertation, we study the vulnerability of current wireless systems to the leakage of transmission attributes at the PHY layer and propose several schemes to prevent it. First, we design and experimentally demonstrate with USRPs an energy-efficient and highly disruptive jamming attack on the FO estimation of an OFDM system. OFDM is the core multiplexing scheme in many modern wireless systems (e.g., LTE/5G and 802.11a/n/ac) and is highly susceptible to FO. FO is the difference in the operating frequencies of two radio oscillators. This estimation is done by the receiver using the publicly-known frame preamble. We show that the leakage of FO value via the preamble can facilitate an optimally designed jamming signal without needing to know the channel between the transmitter and the legitimate receiver. Our results show that the jammer can guarantee a successful attack even when its power is slightly less than the transmitter's power. We then propose four mitigation approaches against the proposed FO attack. Next, we consider certain transmission attributes that are disclosed via unencrypted PHY/MAC headers. Example of these attributes are payload size, transmission rate, and MAC addresses. Beyond unencrypted headers, the adversary can estimate the frame size and transmission rate through identifying the payload's modulation scheme and measuring the transmission time. To prevent the leakage of these attributes, we propose Friendly CryptoJam scheme, which consists of three components: First, a modulation-aware encryption scheme to encrypt the headers. Second, an efficient modulation obfuscation techniques. Specifically, the proposed modulation obfuscation scheme embeds the modulation symbols of a frame's payload into the constellation of the highest-order modulation scheme supported by the system. Together with effective PHY/MAC header encryption at the modulation level, the proposed obfuscation scheme hides the transmission rate, payload size, and other attributes announced in the headers while avoiding any BER performance loss. Compared with prior art, Friendly CryptoJam enjoys less complexity and less susceptibility to FO estimation errors. The third component is a novel PHY-level identification method. To facilitate PHY/MAC header encryption when a MAC layer sender identifier cannot be used (e.g., due to MAC address encryption), we propose two preamble-based sender identification methods, one for OFDM and one for non-OFDM systems. A sender identifier is special message that can be embedded in the frame preamble. The extent of the applications of our embedding scheme goes beyond identifier embedding and include embedding part of the data frame, the sender's digital signature, or any meta-data that the sender provides. Our message embedding method can further be used to mitigate the FO estimation attack because the jammer can no longer optimize its jamming signal with respect to a fixed preamble signal. In addition, we considered friendly jamming technique in a multi-link/hop network to degrade the channels of the eavesdroppers and prevent successful decoding of the headers, while minimizing the required jamming power by optimally placing the friendly jamming devices.
    • Object and spatial memory in fetal alcohol syndrome: An assessment of hippocampal dysfunction.

      Uecker, Anne Cantalupo.; Nadel, Lynn; Rosser, Rosemary; Copple, Peggy; Kaszniak, Alfred W.; McNaughton, Bruce (The University of Arizona., 1993)
      Fetal alcohol syndrome (FAS), a leading cause of mental retardation, was initially described in the United States only twenty years ago. Because it is likely that fetal alcohol exposure contributes substantially to the heterogeneously-grouped learning disabled population, it is worthwhile to review the known cognitive and neurobiological bases of this syndrome, and to test promising neuropsychological hypotheses. For example, animal models of FAS indicate neuroanatomical and behavioral deficits attributable to dysfunction of the hippocampus, a neural structure important in learning and especially spatial memory. In addition, although humans with FAS have demonstrated difficulty with nonverbal problems that are spatial in nature, no specific tests of hippocampal dysfunction have been administered. Thus, fifteen children (x age = 9.8 ± 2.32) with alcohol related birth defects (ARBD), and 15 control children (x age = 9.7 ± 2.40) were tested on several spatial and object memory tasks. These tasks were administered in (1) a small-scale desk-work type environment, and (2) a large-scale environment designed to parallel animal work. The spatial tasks were presumed to be indicators of intact hippocampal functioning, but the object memory tasks were not. As expected, individuals with ARBD consistently demonstrated a deficit spatial memory performance. There was never a significant difference on an immediate object recall task, but the children with ARBD tended "to forget" more objects after a delay in two of the three experiments. Previous research emphasizes the role of the hippocampus in spatial memory (Morris, Garrud, Rawlins, & O'Keefe, 1982) as well as in visually-mediated delayed object recall. Left neocortical structures that subserve immediate object recall appear to be relatively intact. Visuospatial descriptive testing indicated a further disturbance in nonverbal information processing that could involve such neuroanatomical structures as the frontal lobe, parietal cortex, basal ganglia, corpus callosum, and cerebellum. Further studies that address intact vs. deficit performance in children with ARBD could illuminate some specific structural-functional attributes in the brains of children. Defining the neurodevelopmental role of the hippocampus in learning and memory is a priority to be accomplished.
    • Object Category Formation in 4.5 Month-Old Infants

      Bishop, Keri Elizabeth (The University of Arizona., 2011-05)
    • Object Discrimination Using Electrotactile Feedback

      Fuglevand, Andrew J.; Bailey, Elizabeth Fiona; Arakeri, Tapas Jaywant; Fuglevand, Andrew J.; Bailey, Elizabeth Fiona; Fregosi, Ralph F.; Eggers, Erika D. (The University of Arizona., 2017)
      A variety of bioengineering systems are being developed to restore the sense of touch in individuals who have lost this mode of sensory feedback because of spinal cord injury, stroke, or amputation. Typically, these systems detect touch pressure on the fingers of an insensate hand (or from a prosthetic hand in the case of amputees) and deliver the detected pressure information to sensate skin above the site of injury (for example, on the back of the neck) by electrically stimulating that skin with an intensity that matches the detected pressure. We implemented a project that involves developing a method to artificially represent tactile and proprioceptive sensations using electrotactile feedback in prosthetic users. Our system uses one set of electrodes to provide information about contact forces applied by the digits and a separate set to indicate aperture of the hand. We tested the ability of five intact human subjects to distinguish objects of varying weight, width and compliance based on electrotactile feedback arising from sensors placed on the hand of an experimenter (not visible to the subject) grasping and lifting the test objects. Over the course of five separate training sessions, we observed a statistically significant (P=0.026) improvement in the mean performance of all subjects. Thus, this study serves as proof that human subjects can learn to make sense of multichannel-multivariable electrotactile feedback to comprehend certain physical features associated with an object.
    • An object oriented approach to finite element analysis and multi-body dynamic analysis program designs

      Arabyan, Ara; Sagal, Ellen Jean, 1954- (The University of Arizona., 1993)
      Procedurally-oriented computer programs used to perform finite element and multibody dynamics analyses are difficult to understand, use, and modify. A new approach, object-oriented programming, was used to develop a finite element code that is easier to apply, understand, and modify. Object-oriented code is easier to understand, as the characteristics and operations associated with a physical phenomena are grouped in a class whose structure closely parallels the modeled entity. Elements, bodies, joints, and mechanisms are modeled as classes. Program application is facilitated by a hierarchy of class structure. Manipulation of higher level body and mechanism class types direct the complicated, lower level code of element calculations. Lower level code is hidden in an object library resulting in a shorter, simpler driver program for an analysis. Modification and expansion of programs is easily accomplished through object-oriented language features such as modularization of code into classes and overloaded functions. Body and element abstract base classes provide "templates" for creation of new type classes used to develop additional analyses.
    • Object Recognition and Classification

      Johnson, Taylor Christine (The University of Arizona., 2012-05)
      Object recognition and classification is a common problem facing computers. There are many shortcomings in proper identification of an object when it comes to computer algorithms. A very common process used to deal with classification problems is neural networks. Neural networks are modelled after the human brain and the neuron _rings that occur when an individual looks at an image and identifies the objects in it. In this work we propose a probabilistic neural network that takes into account the regional properties of an image of either an ant or an egg as determined by edge segmentation and an extraction of geometric features specific to the object. To do this the algorithm calculates the regional properties of a black and white representation of the object and then gives these properties to the probabilistic neural network which calculates the probability of the object being an ant or an egg.
    • An object-oriented environment for system structuring

      Rozenbilt, Jerzy W.; Hover, Edward Martin, 1954- (The University of Arizona., 1991)
      This thesis describes the design and implementation of a structured knowledge representation scheme within an object-oriented environment. The knowledge representation scheme is based on the system entity structure (SES), a labeled tree-like graph which can be used to represent families of systems. The object-oriented environment is the Knowledge Representation for Object-oriented Simulation (KROS). A brief introduction to these two systems is made and a design of an automated model structuring system based on them is discussed. A detailed example based on a visual flight simulation graphical display system (GDS) is developed to demonstrate features of the model structuring system and show its utility. The SES has been implemented within KROS and does contribute formal ideas for decomposing systems. Implementing the SES within KROS allowed the use of the object-oriented methodology that KROS provides for algorithm implementation. The standardization provided by the Common LISP language allows the resulting system to be used on a variety of machines.
    • Object-oriented remote consultation and diagnosis in global PACS using multi-thread Java

      Martinez, Ralph; Yu, Yuan-Pin, 1967- (The University of Arizona., 1996)
      Designing an integrated portable, object-oriented, real-time multimedia remote consultation and diagnosis (RCD) system for Global PACS has been a research challenge for the past years. There are many specialties in the medical environment, generating multimedia information. During a diagnosis, physicians need to refer to other cases, medical references and other physicians. Continuing medical education and exchanging experience among physicians are critical items to improve the quality of diagnosis. In clinical telemedicine, there is a need to have a viewing workstation serving different purposes in an heterogeneous medical environment. This viewing workstation must be portable and flexible to meet the needs of various medical specialties. The objective of this research is to perform an object oriented analysis and design for a Global PACS environment and implement in Java. In this research, the Java programming environment is used. Object-oriented Java is portable across several platforms. It has a Graphics User Interface (GUI) package, a network package, a Web package, a security package and a thread package. In this research, common objects are defined and implemented for the RCD system. The GUI part can be customized to fit different purposes. This development is performed in the context of a Global PACS environment. The Global PACS RCD has three major program components: the diagnosis component, the education component and management component. These components all share the same common objects and methods. The software modules are designed to run as stand-alone Java applications and as applets in the Java-enabled Web browsers. Physicians can use it to do diagnosis of store and forward cases on-line or off-line in a Global PACS. Students can check out cases and turn in their diagnosis from the Web browser. A system manager can manage the RCD workstations and Global PACS database from the same workstation. Performance tests of the object oriented Java software show a performance equal or better to previous RCD implementation in Global PACS.
    • The Objective Grading of Original Unaccompanied Four-Mallet Solo Vibraphone Literature

      Weinberg, Norman; Hewitt, Jeffrey Allen; Weinberg, Norman; Reid, Edward; Thomas, Kelly (The University of Arizona., 2014)
      An important resource in many areas of music is the availability of standardized graded databases of literature for solo instruments. These databases provide a progression of technical abilities that help musicians follow a proper path in developing new skills. Currently in the area of percussion, there are no graded databases for solo vibraphone literature. While there are several sources that contain subjective graded music lists, none of these sources have a standardized approach in defining each of their difficulty levels, and this creates contradicting information for particular pieces. The goal of this research is to present the first standardized and systematic approach to grading the difficulty levels of vibraphone literature. Influenced by pianist Jane Magrath's reference guide of piano teaching literature and percussionist Julia Gaines' research project on marimba repertoire, this research is modeled on Gaines' objective analysis document used to grade marimba literature with ten different levels of difficulty. With the exception of dampening and pedaling, all of the technical aspects required for playing the vibraphone remain the same as the marimba. Because musical considerations are subjective in nature, only the quantifiable technical considerations are used for grading each work in an objective manner. The technical difficulty of original unaccompanied four-mallet solo vibraphone literature is assessed through the analysis of stroke speed, interval size, wrist turns, manual changes, independence, dampening, and pedaling. Each piece's grade will be classified based on the highest level of technical difficulty found in the music. The selection of vibraphone literature for this research comes from pieces found on prescribed state music lists and university handbook recommendation lists. Annotations are included to describe the pieces that are particularly mislabeled, and a discussion regarding the performance challenges that each piece presents are offered. Three annotations from each of the ten difficulty levels contain a justification based on the results recorded in the analysis document. With an extensive graded database containing over one hundred seventy vibraphone pieces listed in the appendix, this resource will assist percussion students and educators in selecting appropriate vibraphone literature to study and perform within a proper progression from one work to another.
    • Objective Measures of Tropical Cyclone Intensity and Formation from Satellite Infrared Imagery

      Ritchie, Elizabeth A; Tyo, J Scott; Pineros, Miguel F.; Ritchie, Elizabeth A; Tyo, J Scott; Gehm, Michael (The University of Arizona., 2009)
      This document proposes an objective technique to estimate the intensity and predict the formation of tropical cyclones using infrared satellite imagery. As the tropical cyclone develops from an unstructured cloud cluster and intensifies the cloud structures become more axisymmetric around an identified reference point or center. This methodology processes the image gradient to measure the level of symmetry of cloud structures, which characterizes the degree of cloud organization of the tropical cyclone.The center of a cloud system is calculated by projecting and accumulating parallel lines to the gradient vectors. The point where the highest number of line intersections is located pinpoints a common point where the corresponding gradients are directed. This location is used as the center of the system. Next, a procedure that characterizes the departure of the weather system structure from axisymmetry is implemented. The deviation angle of each gradient vector relative to a radial line projected from the center is calculated. The variance of the set of deviation angles enclosed by a circular area around the center describes the axisymmetry of the system, and its behavior through time depicts its dynamics. Results are presented that show the time series of the deviation angle variances is well correlated with the National Hurricane Center best-track estimates.The formation of tropical cyclones is detected by extending the deviation-angle variance technique, it is calculated using every pixel in the scene as the center of the cloud system. Low angle variances indicate structures with high levels of axisimmetry, and these values are compared to a set of thresholds to determine whether a cloud structure can be considered as a vortex. The first detection in a sequence indicates a nascent storm. It was found that 86% of the tropical cyclones during 2004 and 2005 were detected 27 h on average before the National Hurricane Center classified them as tropical storms (33kt).Finally, two procedures to locate the center of a tropical cyclone are compared to the National Hurricane Center best-track center database. Results show that both techniques provide similar accuracy, which increases as the tropical cyclone evolves.