78 results on '"Challa M"'
Search Results
2. Theoretical Models for Adsorption and Diffusion of In on Cu(100)
- Author
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Challa, M. S. S., Li, Yi, Press, M. R., Khanna, S. N., Jena, P., Yousouff, M., Lotsch, H. K. V., editor, Landau, David P., editor, Mon, K. K., editor, and Schüttler, Heinz-Bernd, editor
- Published
- 1990
- Full Text
- View/download PDF
3. AE-CNN Based Supervised Image Classification
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Chandra, G., Challa, M., Chandra, G., and Challa, M.
- Abstract
Point of Care Ultrasound (PoCUS) imaging is an important tool in detecting lung consolidations and tissue sliding, and hence has a potential to identify the onset of novel-CoVID-19 attack in a person. Of late, Convolutional Neural Network (CNN) architectures have gained popularity in improving the accuracy of the predictions. Motivated by this, in this paper, we introduce a CNN based Auto Encoder (AE-CNN) for a better representation of the features to get an accurate prediction. While most of the existing models contain ‘fully connected’ (FC) layers, in our work, we use only convolutional layers instead of FC layers before the output layer, which helps us in achieving a less training time of the model. Moreover, fully connected layers of a network can not learn the patterns in an image as much as convolutional layers can. This is the main advantage of our model over its existing counterparts. We demonstrate that our model detects the lung abnormalities in the ultrasound images with an accuracy of 96.6%.
- Published
- 2021
4. An analysis of West African dynamics using a linearized GCM
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Nicholson, S.E., Barcilon, A.I., and Challa, M.
- Subjects
West Africa -- Environmental aspects ,Fluid dynamics -- Research ,Convection (Meteorology) -- Observations ,Dynamic meteorology -- Research ,Earth sciences ,Science and technology - Abstract
This study utilizes a linear, primitive equation spherical model to study the development and propagation of easterly wave disturbances over West Africa. Perturbations are started from an initial disturbance consisting of a barotropic vortex and the governing equations are integrated forward in time. The perturbations are introduced into basic states corresponding to the observed dynamical and thermodynamical characteristics of two wet years in the Sahel and two dry years. The model simulations show consistent contrasts in wave activity between the wet and dry years. The waves are markedly stronger in the wet years and show a barotropic structure throughout the troposphere. The waves tend to extend throughout the troposphere to the level of the tropical easterly jet (TEJ) in the wet years, but not in the dry years. The upper-tropospheric shear, which is stronger in wet years, appears to be a key factor in wave development. This shear is dependent on the intensity of the TEJ, suggesting that the TEJ is an important factor in interannual variability in the Sahel. When the overall shear is weak, vertical development is suppressed. Another contrast is that in the dry years the growth rates show a single maximum around 3000-4000 km, but in the wet years there is a second, around 6000-7000 km. This suggests that both synoptic-scale and planetary-scale waves are active in the rainy season of some wet years. Imposing considerations of potential vorticity, the generation of planetary-scale waves implies a strong link between the surface and the TEJ in wet years. Such a link is absent in the dry years. This is likely a major factor in the interannual variability of rainfall in the Sahel.
- Published
- 2008
5. Wave activity on the tropical easterly jet
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Nicholson, S.E., Barcilon, A.I., Challa, M., and Baum, J.
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West Africa -- Environmental aspects ,Tropics -- Environmental aspects ,Air jets -- Models ,Atmospheric circulation -- Observations ,Earth sciences ,Science and technology - Abstract
This article examines the question of the existence of waves on the tropical easterly jet (TEJ) over West Africa. The TEJ is a well-known feature of the Asian monsoon and waves on the jet have been implicated in various weather phenomena. Its role in West African meteorology has received little attention. A model simulation of wet and dry years over West Africa predicted wave development on the TEJ. NCEP reanalysis data confirmed the existence of these waves, using case studies in the dry year 1983 and the wet year 1950. Both the simulated and observed waves are of planetary scale, with a period of 5-6 days. Potential vorticity (PV) theory suggests that they develop via interactions between the surface and the TEJ. Overall, the results suggest that interactions between the TEJ and African easterly jet play an important role in the development of wave disturbances over West Africa.
- Published
- 2007
6. Image Mission Attitude Support Experiences
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Ottenstein, N, Challa, M, Home, A, Harman, R, and Burley, R
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Astrodynamics - Abstract
The spin-stabilized Imager for Magnetopause to Aurora Global Exploration (IMAGE) is the National Aeronautics and Space Administration's (NASA's) first Medium-class Explorer Mission (MIDEX). IMAGE was launched into a highly elliptical polar orbit on March 25, 2000 from Vandenberg Air Force Base, California, aboard a Boeing Delta II 7326 launch vehicle. This paper presents some of the observations of the flight dynamics analyses during the launch and in-orbit checkout period through May 18, 2000. Three new algorithms - one algebraic and two differential correction - for computing the parameters of the coning motion of a spacecraft are described and evaluated using in-flight data from the autonomous star tracker (AST) on IMAGE. Other attitude aspects highlighted include support for active damping consequent upon the failure of the passive nutation damper, performance evaluation of the AST, evaluation of the Sun sensor and magnetometer using AST data, and magnetometer calibration.
- Published
- 2001
7. Magnetometer-Only Attitude and Rate Estimates for Spinning Spacecraft
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Challa, M, Natanson, G, and Ottenstein, N
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Spacecraft Design, Testing And Performance - Abstract
A deterministic algorithm and a Kalman filter for gyroless spacecraft are used independently to estimate the three-axis attitude and rates of rapidly spinning spacecraft using only magnetometer data. In-flight data from the Wide-Field Infrared Explorer (WIRE) during its tumble, and the Fast Auroral Snapshot Explorer (FAST) during its nominal mission mode are used to show that the algorithms can successfully estimate the above in spite of the high rates. Results using simulated data are used to illustrate the importance of accurate and frequent data.
- Published
- 2000
8. Submillimeter Wave Astronomy Satellite (SWAS) Launch and Early Orbit Support Experiences
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Kirschner, S, Sedlak, J, Challa, M, Nicholson, A, Calder, A, Sande, C, and Rohrbaugh, D
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Spacecraft Design, Testing And Performance - Abstract
The Submillimeter Wave Astronomy Satellite (SWAS) was successfully launched on December 6, 1998 at 00:58 UTC. The two year mission is the fourth in the series of Small Explorer (SMEX) missions. SWAS is dedicated to the study of star formation and interstellar chemistry. SWAS was injected into a 635 km by 650 km orbit with an inclination of nearly 70 deg by an Orbital Sciences Corporation Pegasus XL launch vehicle. The Flight Dynamics attitude and navigation teams supported all phases of the early mission. This support included orbit determination, attitude determination, real-time monitoring, and sensor calibration. This paper reports the main results and lessons learned concerning navigation, support software, star tracker performance, magnetometer and gyroscope calibrations, and anomaly resolution. This includes information on spacecraft tip-off rates, first-day navigation problems, target acquisition anomalies, star tracker anomalies, and significant sensor improvements due to calibration efforts.
- Published
- 1999
9. Effects of magnetometer calibration and maneuvers on accuracies of magnetometer-only attitude-and-rate determination
- Author
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Challa, M and Natanson, G
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Astrodynamics - Abstract
Two different algorithms - a deterministic magnetic-field-only algorithm and a Kalman filter for gyroless spacecraft - are used to estimate the attitude and rates of the Rossi X-Ray Timing Explorer (RXTE) using only measurements from a three-axis magnetometer. The performance of these algorithms is examined using in-flight data from various scenarios. In particular, significant enhancements in accuracies are observed when' the telemetered magnetometer data are accurately calibrated using a recently developed calibration algorithm. Interesting features observed in these studies of the inertial-pointing RXTE include a remarkable sensitivity of the filter to the numerical values of the noise parameters and relatively long convergence time spans. By analogy, the accuracy of the deterministic scheme is noticeably lower as a result of reduced rates of change of the body-fixed geomagnetic field. Preliminary results show the filter-per-axis attitude accuracies ranging between 0.1 and 0.5 deg and rate accuracies between 0.001 deg/sec and 0.005 deg./sec, whereas the deterministic method needs a more sophisticated techniques for smoothing time derivatives of the measured geomagnetic field to clearly distinguish both attitude and rate solutions from the numerical noise. Also included is a new theoretical development in the deterministic algorithm: the transformation of a transcendental equation in the original theory into an 8th-order polynomial equation. It is shown that this 8th-order polynomial reduces to quadratic equations in the two limiting cases-infinitely high wheel momentum, and constant rates-discussed in previous publications.
- Published
- 1998
10. Accuracy Studies of a Magnetometer-Only Attitude-and-Rate-Determination System
- Author
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Challa, M and Wheeler, C
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Astrodynamics - Abstract
A personal computer based system was recently prototyped that uses measurements from a three axis magnetometer (TAM) to estimate the attitude and rates of a spacecraft using no a priori knowledge of the spacecraft's state. Past studies using in-flight data from the Solar, Anomalous, and Magnetospheric Particles Explorer focused on the robustness of the system and demonstrated that attitude and rate estimates could be obtained accurately to 1.5 degrees (deg) and 0.01 deg per second (deg/sec), respectively, despite limitations in the data and in the accuracies of te truth models. This paper studies the accuracy of the Kalman filter in the system using several orbits of in-flight Earth Radiation Budget Satellite (ERBS) data and attitude and rate truth models obtained from high precision sensors to demonstrate the practical capabilities. This paper shows the following: Using telemetered TAM data, attitude accuracies of 0.2 to 0.4 deg and rate accuracies of 0.002 to 0.005 deg/sec (within ERBS attitude control requirements of 1 deg and 0.0005 deg/sec) can be obtained with minimal tuning of the filter; Replacing the TAM data in the telemetry with simulated TAM data yields corresponding accuracies of 0.1 to 0.2 deg and 0.002 to 0.005 deg/sec, thus demonstrating that the filter's accuracy can be significantly enhanced by further calibrating the TAM. Factors affecting the fillter's accuracy and techniques for tuning the system's Kalman filter are also presented.
- Published
- 1996
11. A PC-based magnetometer-only attitude and rate determination system for gyroless spacecraft
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Challa, M, Natanson, G, Deutschmann, J, and Galal, K
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Astrodynamics - Abstract
This paper describes a prototype PC-based system that uses measurements from a three-axis magnetometer (TAM) to estimate the state (three-axis attitude and rates) of a spacecraft given no a priori information other than the mass properties. The system uses two algorithms that estimate the spacecraft's state - a deterministic magnetic-field only algorithm and a Kalman filter for gyroless spacecraft. The algorithms are combined by invoking the deterministic algorithm to generate the spacecraft state at epoch using a small batch of data and then using this deterministic epoch solution as the initial condition for the Kalman filter during the production run. System input comprises processed data that includes TAM and reference magnetic field data. Additional information, such as control system data and measurements from line-of-sight sensors, can be input to the system if available. Test results are presented using in-flight data from two three-axis stabilized spacecraft: Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) (gyroless, Sun-pointing) and Earth Radiation Budget Satellite (ERBS) (gyro-based, Earth-pointing). The results show that, using as little as 700 s of data, the system is capable of accuracies of 1.5 deg in attitude and 0.01 deg/s in rates; i.e., within SAMPEX mission requirements.
- Published
- 1995
12. Earth horizon modeling and application to static Earth sensors on TRMM spacecraft
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Keat, J, Challa, M, Tracewell, D, and Galal, K
- Subjects
Astrodynamics - Abstract
Data from Earth sensor assemblies (ESA's) often are used in the attitude determination (AD) for both spinning and Earth-pointing spacecraft. The ESA's on previous such spacecraft for which the ground-based AD operation was performed by the Flight Dynamics Division (FDD) used the Earth scanning method. AD on such spacecraft requires a model of the shape of the Earth disk as seen from the spacecraft. AD accuracy requirements often are too severe to permit Earth oblateness to be ignored when modeling disk shape. Section 2 of this paper reexamines and extends the methods for Earth disk shape modeling employed in AD work at FDD for the past decade. A new formulation, based on a more convenient Earth flatness parameter, is introduced, and the geometric concepts are examined in detail. It is shown that the Earth disk can be approximated as an ellipse in AD computations. Algorithms for introducing Earth oblateness into the AD process for spacecraft carrying scanning ESA's have been developed at FDD and implemented into the support systems. The Tropical Rainfall Measurement Mission (TRMM) will be the first spacecraft with AD operation performed at FDD that uses a different type of ESA - namely, a static one - containing four fixed detectors D(sub i) (i = 1 to 4). Section 3 of this paper considers the effect of Earth oblateness on AD accuracy for TRMM. This effect ideally will not induce AD errors on TRMM when data from all four D(sub i) are present. When data from only two or three D(sub i) are available, however, a spherical Earth approximation can introduce errors of 0.05 to 0.30 deg on TRMM. These oblateness-induced errors are eliminated by a new algorithm that uses the results of Section 2 to model the Earth disk as an ellipse.
- Published
- 1995
13. Magnetometer-only attitude and rate determination for a gyro-less spacecraft
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Natanson, G. A, Challa, M. S, Deutschmann, J, and Baker, D. F
- Subjects
Space Communications, Spacecraft Communications, Command And Tracking - Abstract
Attitude determination algorithms that requires only the earth's magnetic field will be useful for contingency conditions. One way to determine attitude is to use the time derivative of the magnetic field as the second vector in the attitude determination process. When no gyros are available, however, attitude determination becomes difficult because the rates must be propagated via integration of Euler's equation, which in turn requires knowledge of the initial rates. The spacecraft state to be determined must then include not only the attitude but also rates. This paper describes a magnetometer-only attitude determination scheme with no a priori knowledge of the spacecraft state, which uses a deterministic algorithm to initialize an extended Kalman filter. The deterministic algorithm uses Euler's equation to relate the time derivatives of the magnetic field in the reference and body frames and solves the resultant transcendental equations for the coarse attitude and rates. An important feature of the filter is that its state vector also includes corrections to the propagated rates, thus enabling it to generate highly accurate solutions. The method was tested using in-flight data from the Solar, Anomalous, and Magnetospheric Particles Explorer (SAMPEX), a Small Explorer spacecraft. SAMPEX data using several eclipse periods were used to simulate conditions that may exist during the failure of the on-board digital sun sensor. The combined algorithm has been found effective, yielding accuracies of 1.5 deg in attitude (within even nominal mission requirements) and 0.01 degree per second (deg/sec) in the rates.
- Published
- 1994
14. Advantages of estimating rate corrections during dynamic propagation of spacecraft rates: Applications to real-time attitude determination of SAMPEX
- Author
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Challa, M. S, Natanson, G. A, Baker, D. F, and Deutschmann, J. K
- Subjects
Spacecraft Design, Testing And Performance - Abstract
This paper describes real-time attitude determination results for the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), a gyroless spacecraft, using a Kalman filter/Euler equation approach denoted the real-time sequential filter (RTSF). The RTSF is an extended Kalman filter whose state vector includes the attitude quaternion and corrections to the rates, which are modeled as Markov processes with small time constants. The rate corrections impart a significant robustness to the RTSF against errors in modeling the environmental and control torques, as well as errors in the initial attitude and rates, while maintaining a small state vector. SAMPLEX flight data from various mission phases are used to demonstrate the robustness of the RTSF against a priori attitude and rate errors of up to 90 deg and 0.5 deg/sec, respectively, as well as a sensitivity of 0.0003 deg/sec in estimating rate corrections in torque computations. In contrast, it is shown that the RTSF attitude estimates without the rate corrections can degrade rapidly. RTSF advantages over single-frame attitude determination algorithms are also demonstrated through (1) substantial improvements in attitude solutions during sun-magnetic field coalignment and (2) magnetic-field-only attitude and rate estimation during the spacecraft's sun-acquisition mode. A robust magnetometer-only attitude-and-rate determination method is also developed to provide for the contingency when both sun data as well as a priori knowledge of the spacecraft state are unavailable. This method includes a deterministic algorithm used to initialize the RTSF with coarse estimates of the spacecraft attitude and rates. The combined algorithm has been found effective, yielding accuracies of 1.5 deg in attitude and 0.01 deg/sec in the rates and convergence times as little as 400 sec.
- Published
- 1994
15. Real-time attitude determination and gyro calibration
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Challa, M, Filla, O, Sedlak, J, and Chu, D
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Astrodynamics - Abstract
We present results for two real-time filters prototyped for the Compton Gamma Ray Observatory (GRO), the Extreme Ultraviolet Explorer (EUVE), the Cosmic Background Explorer (COBE), and the next generation of Geostationary Operational Environmental Satellites (GOES). Both real and simulated data were used to solve for attitude and gyro biases. These filters promise advantages over single-frame and batch methods for missions like GOES, where startup and transfer-orbit operations require quick knowledge of attitude and gyro biases.
- Published
- 1993
16. Monte Carlo Simulations Using the Gaussian Ensemble
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Challa, M. S. S., Hetherington, J. H., Lotsch, H. K. V., editor, Landau, David P., editor, Mon, K. K., editor, and Schüttler, Heinz-Bernd, editor
- Published
- 1988
- Full Text
- View/download PDF
17. Model Development of Atlantic Hurricanes from Prehurricane Cloud Clusters, Depressions and Cyclones
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Pfeffer, R. L., Challa, M., Ghil, Michael, editor, Sündermann, Jürgen, editor, Sadourny, Robert, editor, Bengtsson, Lennart, editor, and Lighthill, James, editor
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- 1982
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18. Spin-Dynamics Studies of Excitations in xy- Chains
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Landau, D. P., Gerling, R. W., Challa, M. S. S., Lotsch, H. K. V., editor, Balucani, Umberto, editor, Lovesey, Stephen W., editor, Rasetti, Mario G., editor, and Tognetti, Valerio, editor
- Published
- 1987
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19. The association between childhood maltreatment, psychopathology, and adult sexual victimization in men and women: results from three independent samples
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Werner, K. B., primary, McCutcheon, V. V., additional, Challa, M., additional, Agrawal, A., additional, Lynskey, M. T., additional, Conroy, E., additional, Statham, D. J., additional, Madden, P. A. F., additional, Henders, A. K., additional, Todorov, A. A., additional, Heath, A. C., additional, Degenhardt, L., additional, Martin, N. G., additional, Bucholz, K. K., additional, and Nelson, E. C., additional
- Published
- 2015
- Full Text
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20. Excitations in the classical XY chain.
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Gerling, R. W., Landau, D. P., and Challa, M. S. S.
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MAGNETIC fields ,EQUATIONS of motion ,MONTE Carlo method - Abstract
Studies the time-dependent behavior of the XY chain in a symmetry breaking magnetic field using spin-dynamics method in which the equations of motion are integrated using starting configurations determined by Monte Carlo simulations. Method of the study; results and discussion; Conclusion.
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- 1988
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21. Magnetometer-only attitude and rate estimates during the Earth Radiation Budget Satellite 1987 control anomaly
- Author
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Challa, M., primary, Kotaru, S., additional, Natanson, G., additional, and Challa, M., additional
- Published
- 1997
- Full Text
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22. Magnetometer-only attitude and rate estimates for spinning spacecraft
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Challa, M., primary, Natanson, G., additional, and Ottenstein, N., additional
- Published
- 2000
- Full Text
- View/download PDF
23. A new magnetometer calibration algorithm and applications
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Challa, M., primary and Harman, R., additional
- Published
- 1998
- Full Text
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24. Multi-agent design architecture for Integrated Design Systems
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Deshmukh, A., primary, Middelkoop, T., additional, Krothapalli, A., additional, Shields, W., additional, Zhang, C., additional, Chandra, N., additional, Challa, M., additional, and Smith, C., additional
- Published
- 1998
- Full Text
- View/download PDF
25. Simultaneous determination of spacecraft attitude and rates using only a magnetometer
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Challa, M., primary, Natanson, G., additional, and Wheeler, C., additional
- Published
- 1996
- Full Text
- View/download PDF
26. Liuet al. reply
- Author
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Liu, Feng, primary, Challa, M., additional, Khanna, S. N., additional, and Jena, P., additional
- Published
- 1990
- Full Text
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27. Monte Carlo studies of finite-size effects at first-order transitions
- Author
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Challa, M. S. S., primary, Landau, D. P., additional, and Binder, K., additional
- Published
- 1990
- Full Text
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28. Theory of hydrogen pairing in yttrium
- Author
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Liu, Feng, primary, Challa, M., additional, Khanna, S. N., additional, and Jena, P., additional
- Published
- 1989
- Full Text
- View/download PDF
29. Excitations in the classical X Y chain
- Author
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Gerling, R. W., primary, Landau, D. P., additional, and Challa, M. S. S., additional
- Published
- 1988
- Full Text
- View/download PDF
30. Alkaloid-based modulators of the PI3K/Akt/mTOR pathway for cancer therapy: Understandings from pharmacological point of view.
- Author
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Mokhfi FZ, Al Amin M, Zehravi M, Sweilam SH, Arjun UVNV, Gupta JK, Vallamkonda B, Balakrishnan A, Challa M, Singh J, Prasad PD, Ali SS, Ahmad I, Doukani K, and Emran TB
- Subjects
- Humans, Animals, Antineoplastic Agents pharmacology, Antineoplastic Agents therapeutic use, Antineoplastic Agents chemistry, TOR Serine-Threonine Kinases metabolism, Neoplasms drug therapy, Neoplasms metabolism, Alkaloids pharmacology, Alkaloids chemistry, Alkaloids therapeutic use, Proto-Oncogene Proteins c-akt metabolism, Signal Transduction drug effects, Phosphatidylinositol 3-Kinases metabolism
- Abstract
This review aims to summarize the role of alkaloids as potential modulators of the PI3K/Akt/mTOR (PAMT) pathway in cancer therapy. The PAMT pathway plays a critical role in cell growth, survival, and metabolism, and its dysregulation contributes to cancer hallmarks. In healthy cells, this pathway is tightly controlled. However, this pathway is frequently dysregulated in cancers and becomes abnormally active. This can happen due to mutations in genes within the pathway itself or due to other factors. This chronic overactivity promotes cancer hallmarks such as uncontrolled cell division, resistance to cell death, and increased blood vessel formation to nourish the tumor. As a result, the PAMT pathway is a crucial therapeutic target for cancer. Researchers are developing drugs that specifically target different components of this pathway, aiming to turn it off and slow cancer progression. Alkaloids, a class of naturally occurring nitrogen-containing molecules found in plants, have emerged as potential therapeutic agents. These alkaloids can target different points within the PAMT pathway, inhibiting its activity and potentially resulting in cancer cell death or suppression of tumor growth. Research is ongoing to explore the role of various alkaloids in cancer treatment. Berberine reduces mTOR activity and increases apoptosis by targeting the PAMT pathway, inhibiting cancer cell proliferation. Lycorine inhibits Akt phosphorylation and mTOR activation, increasing pro-apoptotic protein production and decreasing cell viability. In glioblastoma models, harmine suppresses mTORC1. This review focuses on alkaloids such as evodiamine, hirsuteine, chaetocochin J, indole-3-carbinol, noscapine, berberine, piperlongumine, and so on, which have shown promise in targeting the PAMT pathway. Clinical studies evaluating alkaloids as part of cancer treatment are underway, and their potential impact on patient outcomes is being investigated. In summary, alkaloids represent a promising avenue for targeting the dysregulated PAMT pathway in cancer, and further research is warranted., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)
- Published
- 2024
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31. Discovery of novel natural-product-derived mutant isocitrate dehydrogenases 1 inhibitors: Structure-based virtual screening, biological evaluation and structure-activity relationship study.
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Xu T, Yang J, Li D, Challa M, Zou C, Deng P, Zhang SL, and Xu B
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- Humans, Structure-Activity Relationship, Animals, Mice, Molecular Structure, Mutation, Cell Line, Tumor, Drug Evaluation, Preclinical, Neoplasms, Experimental drug therapy, Neoplasms, Experimental pathology, Neoplasms, Experimental metabolism, Isocitrate Dehydrogenase antagonists & inhibitors, Isocitrate Dehydrogenase genetics, Isocitrate Dehydrogenase metabolism, Biological Products pharmacology, Biological Products chemistry, Biological Products chemical synthesis, Enzyme Inhibitors pharmacology, Enzyme Inhibitors chemistry, Enzyme Inhibitors chemical synthesis, Cell Proliferation drug effects, Antineoplastic Agents pharmacology, Antineoplastic Agents chemistry, Antineoplastic Agents chemical synthesis, Drug Discovery, Drug Screening Assays, Antitumor, Dose-Response Relationship, Drug
- Abstract
Mutations in IDH1 are commonly observed across various cancers, causing the conversion of α-KG to 2-HG. Elevated levels of 2-HG disrupt histone and DNA demethylation processes, promoting tumor development. Consequently, there is substantial interest in developing small molecule inhibitors targeting the mutant enzymes. Herein, we report a structure-based high-throughput virtual screening strategy using a natural products library, followed by hit-to-lead optimization. Through this process, we discover a potent compound, named 11s, which exhibited significant inhibition to IDH1 R132H and IDH1 R132C with IC
50 values of 124.4 and 95.7 nM, respectively. Furthermore, 11s effectively reduced 2-HG formation, with EC50 values of 182 nM in U87 R132H cell, and 84 nM in HT-1080 cell. In addition, 11s significantly reduced U87 R132H and HT-1080 cell proliferation with GC50 values of 3.48 and 1.38 μM, respectively. PK-PD experiments further confirmed that compound 11s significantly decreased 2-HG formation in an HT-1080 xenograft mouse model, resulting in notable suppression of tumor growth without apparent loss in body weight., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)- Published
- 2024
- Full Text
- View/download PDF
32. Vertebral hemangiomas: a review on diagnosis and management.
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Kato K, Teferi N, Challa M, Eschbacher K, and Yamaguchi S
- Subjects
- Humans, Retrospective Studies, Tomography, X-Ray Computed, Male, Female, Middle Aged, Hemangioma therapy, Hemangioma diagnostic imaging, Hemangioma diagnosis, Spinal Neoplasms therapy, Spinal Neoplasms diagnostic imaging, Magnetic Resonance Imaging
- Abstract
Background: Vertebral hemangiomas (VHs) are the most common benign tumors of the spinal column and are often encountered incidentally during routine spinal imaging., Methods: A retrospective review of the inpatient and outpatient hospital records at our institution was performed for the diagnosis of VHs from January 2005 to September 2023. Search filters included "vertebral hemangioma," "back pain," "weakness," "radiculopathy," and "focal neurological deficits." Radiographic evaluation of these patients included plain X-rays, CT, and MRI. Following confirmation of a diagnosis of VH, these images were used to generate the figures used in this manuscript. Moreover, an extensive literature search was conducted using PubMed for the literature review portion of the manuscript., Result: VHs are benign vascular proliferations that cause remodeling of bony trabeculae in the vertebral body of the spinal column. Horizontal trabeculae deteriorate leading to thickening of vertical trabeculae which causes a striated appearance on sagittal magnetic resonance imaging (MRI) and computed tomography (CT), "Corduroy sign," and a punctuated appearance on axial imaging, "Polka dot sign." These findings are seen in "typical vertebral hemangiomas" due to a low vascular-to-fat ratio of the lesion. Contrarily, atypical vertebral hemangiomas may or may not demonstrate the "Corduroy" or "Polka-dot" signs due to lower amounts of fat and a higher vascular component. Atypical vertebral hemangiomas often mimic other neoplastic pathologies, making diagnosis challenging. Although most VHs are asymptomatic, aggressive vertebral hemangiomas can present with neurologic sequelae such as myelopathy and radiculopathy due to nerve root and/or spinal cord compression. Asymptomatic vertebral hemangiomas do not require therapy, and there are many treatment options for vertebral hemangiomas causing pain, radiculopathy, and/or myelopathy. Surgery (corpectomy, laminectomy), percutaneous techniques (vertebroplasty, sclerotherapy, embolization), and radiotherapy can be used in combination or isolation as appropriate. Specific treatment options depend on the lesion's size/location and the extent of neural element compression. There is no consensus on the optimal treatment plan for symptomatic vertebral hemangioma patients, although management algorithms have been proposed., Conclusion: While typical vertebral hemangioma diagnosis is relatively straightforward, the differential diagnosis is broad for atypical and aggressive lesions. There is an ongoing debate as to the best approach for managing symptomatic cases, however, surgical resection is often considered first line treatment for patients with neurologic deficit., (© 2024. The Author(s).)
- Published
- 2024
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33. Discovery of novel Thymol-TPP antibiotics that eradicate MRSA persisters.
- Author
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Tang Z, Feng J, Challa M, Rowthu SR, Xiong S, Zou C, Li J, Verma CS, Peng H, He X, Huang C, and He Y
- Subjects
- Humans, Animals, Mice, Thymol pharmacology, Microbial Sensitivity Tests, Bacteria, Anti-Bacterial Agents pharmacology, Anti-Bacterial Agents therapeutic use, Methicillin-Resistant Staphylococcus aureus, Organophosphorus Compounds
- Abstract
The high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains and the formation of non-growing, dormant "persisters" subsets help bacteria evade antibiotic treatment and enhance bacterial resistance, which poses a serious threat to human life and health. It is urgent to discover novel antibacterial therapies effective against MRSA persisters. Thymol is a common nutraceutical with weak antibacterial and antitumor activities. A series of Thymol triphenylphosphine (TPP) conjugates (TPP-Thy3) was designed and synthesized. These compounds showed significantly improved inhibitory activity against Gram-positive bacteria compared with Thymol. Among them, Thy3d displayed a low probability of resistance selection and showed excellent biocompatibility. Interestingly, Thy3d elicited a rapid killing effect of MRSA persisters (99.999%) at high concentration. Fluorescence experiments, electron microscopy, molecular dynamics simulation and bilayer experiment confirmed that Thy3d conjugates exerted potent antimicrobial activity by disrupting the integrity of the membrane of bacterial even the persister. Furthermore, Thy3d exhibited considerable efficacy in a mouse model of subcutaneous murine MRSA infection. In summary, TPP-Thy3 conjugates are a series of novel antibacterial agents and could serve as a new therapeutic strategy for combating antibiotic resistance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Masson SAS.)
- Published
- 2024
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34. Response to a letter to the editor regarding, "surgical management of symptomatic vertebral hemangiomas: a single institution experience and literature review".
- Author
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Teferi N, Challa M, and Hitchon P
- Subjects
- Humans, Hemangioma surgery, Spinal Neoplasms surgery
- Published
- 2024
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35. Large Suprasellar Dermoid Cyst Excision Through an Endoscopic Transsphenoidal Approach: 2-Dimensional Operative Video.
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Teferi N, Vivanco-Suarez J, Park BJ, Challa M, Graham SM, and Greenlee JDW
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- Humans, Endoscopy methods, Skull, Dermoid Cyst diagnostic imaging, Dermoid Cyst surgery, Central Nervous System Cysts diagnostic imaging, Central Nervous System Cysts surgery
- Published
- 2024
- Full Text
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36. Rare variant of large pediatric glioneuronal tumor with novel MYO5A::NTRK3 fusion: illustrative case.
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Chenoweth D, Syed H, Teferi N, Challa M, Persons JE, Eschbacher KL, Seblani M, and Dlouhy BJ
- Abstract
Background: Glioneuronal tumors (GNTs) comprise a rare class of central nervous system (CNS) neoplasms with varying degrees of neuronal and glial differentiation that predominately affect children and young adults. Within the current 2021 World Health Organization (WHO) classification of CNS tumors, GNTs encompass 14 distinct tumor types. Recently, the use of whole-genome DNA methylation profiling has allowed more precise classification of this tumor group., Observations: A 3-year-old male presented with a 3-month history of increasing head circumference, regression of developmental milestones, and speech delay. Magnetic resonance imaging of the brain was notable for a large left hemispheric multiseptated mass with significant mass effect and midline shift that was treated with near-total resection. Histological and molecular assessment demonstrated a glioneuronal tumor harboring an MYO5A::NTRK3 fusion. By DNA methylation profiling, this tumor matched to a provisional methylation class known as "glioneuronal tumor kinase-fused" (GNT kinase-fused). The patient was later started on targeted therapy with larotrectinib., Lessons: This is the first report of an MYO5A::NTRK3 fusion in a pediatric GNT. GNT kinase-fused is a provisional methylation class not currently included in the WHO classification of CNS tumors. This case highlights the impact of thorough molecular characterization of CNS tumors, especially with the increasing availability of novel gene targeting therapies.
- Published
- 2024
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37. Surgical Management of Craniospinal Axis Solitary Fibrous Tumors: A Single-Institution Case Series and Comprehensive Review of the Literature.
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Piscopo AJ, Chowdhury AJ, Teferi N, Lee S, Challa M, Petronek M, Eschbacher K, Bathla G, Buatti JM, and Hitchon P
- Subjects
- Humans, Retrospective Studies, Prognosis, Neoplasm Recurrence, Local surgery, Severe Fever with Thrombocytopenia Syndrome, Solitary Fibrous Tumors diagnostic imaging, Solitary Fibrous Tumors surgery
- Abstract
Background and Objectives: Meningeal solitary fibrous tumors (SFTs) comprise 0.4% of primary central nervous system neoplasms and carry metastatic potential. Disease course and optimal management are largely unknown, and there is currently no literature rigorously describing neurological outcomes in surgically managed SFTs. We present one of the largest craniospinal SFT series, analyze patient outcomes, and extensively review the associated literature., Methods: All surgically managed SFTs at our institution between January 2005 and March 2023 were retrospectively reviewed. Patient demographics, tumor and radiographic features, treatment, and clinical outcomes were collected. Neurological function was quantified using Frankel grade and Neurologic Assessment in Neuro-Oncology scores. Descriptive statistics, multivariate analysis, log-rank test, and Kaplan-Meier survival analysis were performed., Results: Twenty-one patients satisfied inclusion criteria. Tumor locations included 15 supratentorial, three infratentorial, and three spinal. All patients underwent surgical resection, and 16 (76.2%) underwent radiation. Six (28.6%) patients had tumor recurrence, and three (14.3%) developed metastasis. Younger age and higher postoperative Frankel grade were significantly associated with increased overall survival (OS) ( P = .011, P = .002, respectively). All patients symptomatically improved or stabilized after surgery, and Neurologic Assessment in Neuro-Oncology score ( P = .001) and functional status significantly improved postoperatively (Karnofsky Performance Status: 65.2 ± 25.2 vs 91.4 ± 13.5, P = .001). Sex, adjuvant radiation, and extent of resection were not significantly associated with OS., Conclusion: SFT of the central nervous system is a rare entity with a variable clinical course. Surgical resection was associated with improved postoperative functional and neurological status. Higher postoperative neurological function was significantly associated with OS. Further studies are warranted to validate a standardized treatment algorithm and investigate the efficacy of adjuvant radiation in SFT., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)
- Published
- 2024
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- View/download PDF
38. Coronavirus disease 2019-associated persistent cough and Chiari malformation type I resulting in acute respiratory failure: illustrative case.
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Piscopo AJ, Teferi N, Marincovich A, Challa M, and Dlouhy BJ
- Abstract
Background: Chiari malformation type I (CM-I) is the herniation of cerebellar tonsils through the foramen magnum, potentially resulting in the obstruction of cerebrospinal fluid flow and brainstem compression. Sleep-disordered breathing (SDB) is common in patients with CM-I, and symptomatic exacerbations have been described after Valsalva-inducing stressors. Acute decompensation in the setting of coronavirus disease 2019 (COVID-19) has not been described., Observations: After violent coughing episodes associated with COVID-19 infection, a 44-year-old female developed several months of Valsalva-induced occipital headaches, episodic bulbar symptoms, and worsening SDB, which led to acute respiratory failure requiring mechanical ventilation. Imaging demonstrated 12 mm of cerebellar tonsillar descent below the foramen magnum, dorsal brainstem compression, and syringobulbia within the dorsal medulla. She underwent posterior fossa and intradural decompression with near-complete resolution of her symptoms 6 months postoperatively., Lessons: Although CM-I can remain asymptomatic, Valsalva-inducing stressors, including COVID-19 infection, can initiate or acutely exacerbate symptoms, placing patients at risk for CM-I-associated brainstem dysfunction and, in rare cases, acute respiratory failure. Worsening Valsalva maneuvers can contribute to further cerebellar tonsil impaction, brainstem compression, syringomyelia/syringobulbia, and worsening CM-I intradural pathology. Ventilator support and timely decompressive surgery are paramount, as brainstem compression can reduce central respiratory drive, placing patients at risk for coma, neurological deficits, and/or death.
- Published
- 2023
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39. Surgical management of craniospinal axis malignant peripheral nerve sheath tumors: a single-institution experience and literature review.
- Author
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Chowdhury A, Vivanco-Suarez J, Teferi N, Belzer A, Al-Kaylani H, Challa M, Lee S, Buatti JM, and Hitchon P
- Subjects
- Humans, Male, Female, Adolescent, Young Adult, Adult, Middle Aged, Aged, Retrospective Studies, Treatment Outcome, Neurofibrosarcoma pathology, Nerve Sheath Neoplasms surgery, Nerve Sheath Neoplasms diagnosis, Neurofibromatosis 1 pathology
- Abstract
Background: Malignant peripheral nerve sheath tumor (MPNST) is an exceedingly rare and aggressive tumor, with limited literature on its management. Herein, we present our series of surgically managed craniospinal MPNSTs, analyze their outcomes, and review the literature., Methods: We retrospectively reviewed surgically managed primary craniospinal MPNSTs treated at our institution between January 2005 and May 2023. Patient demographics, tumor features, and treatment outcomes were assessed. Neurological function was quantified using the Frankel grade and Karnofsky performance scores. Descriptive statistics, rank-sum tests, and Kaplan-Meier survival analyses were performed., Results: Eight patients satisfied the inclusion criteria (4 male, 4 female). The median age at presentation was 38 years (range 15-67). Most tumors were localized to the spine (75%), and 3 patients had neurofibromatosis type 1. The most common presenting symptoms were paresthesia (50%) and visual changes (13%). The median tumor size was 3 cm, and most tumors were oval-shaped (50%) with well-defined borders (75%). Six tumors were high grade (75%), and gross total resection was achieved in 5 patients, with subtotal resection in the remaining 3 patients. Postoperative radiotherapy and chemotherapy were performed in 6 (75%) and 4 (50%) cases, respectively. Local recurrence occurred in 5 (63%) cases, and distant metastases occurred in 2 (25%). The median overall survival was 26.7 months. Five (63%) patients died due to recurrence., Conclusions: Primary craniospinal MPNSTs are rare and have an aggressive clinical course. Early diagnosis and treatment are essential for managing these tumors. In this single-center study with a small cohort, maximal resection, low-grade pathology, young age (< 30), and adjuvant radiotherapy were associated with improved survival., (© 2023. BioMed Central Ltd., part of Springer Nature.)
- Published
- 2023
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- View/download PDF
40. Clinical diagnostic and radiographic features of primary spinal atypical teratoid rhabdoid tumors tumor in a pediatric patient: A case report and review of the literature.
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Syed H, Teferi N, Hanson A, Challa M, Eschbacher K, and Hitchon P
- Abstract
Atypical teratoid rhabdoid tumors (ATRTs) are rare embryonal tumors comprising 1-2% of all pediatric CNS neoplasms. Spinal ATRTs are even more uncommon, accounting for 2% of all reported ATRT cases. Despite their rarity, ATRTs affect young children disproportionately and are characterized by a high malignant potential due to a heterogeneous cellular composition and inactivating mutations in the SMARCB1 (90%) and SMARCA4 (10%) genes. A 15-month-old female presented with a 2-week history of decreased lower extremity movement and new-onset need for assistance with ambulation. MRI lumbar spine revealed a contrast-enhancing intradural mass at the L3-L4 level with iso-intensity on T1 and T2 sequences. The patient subsequently underwent subtotal tumor resection (∼80%) given concerns for maintaining neurological function. Final pathology was consistent with spinal ATRT, and she later underwent adjuvant chemoradiation therapy per ACNS0333 protocol. She has since remained in remission with age-appropriate developmental milestones over the past 2 years. ATRTs should be considered in the differential diagnosis of intradural spinal lesions, especially in the pediatric patient population. Clinical course, presentation, and diagnosis is often delayed due to the rarity of these tumors, but contrasted craniospinal MRI is key for diagnosis and histopathology with IHC staining showing loss of INI is confirmatory. While gross total resection is the goal, maximal safe tumor resection should be prioritized in order to preserve neurological function. Adjuvant chemoradiation following gross total/subtotal resection has been shown to significantly improve overall survival., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)
- Published
- 2023
- Full Text
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41. Surgical management of symptomatic vertebral hemangiomas: a single institution experience and literature review.
- Author
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Teferi N, Chowdhury AJ, Mehdi Z, Challa M, Eschbacher K, Bathla G, and Hitchon P
- Subjects
- Humans, Spine surgery, Hemangioma surgery, Vertebroplasty methods, Spinal Neoplasms diagnosis
- Abstract
Vertebral hemangiomas (VHs), formed from a vascular proliferation in bone marrow spaces limited by bone trabeculae, are the most common benign tumors of the spine. While most VHs remain clinically quiescent and often only require surveillance, rarely they may cause symptoms. They may exhibit active behaviors, including rapid proliferation, extending beyond the vertebral body, and invading the paravertebral and/or epidural space with possible compression of the spinal cord and/or nerve roots ("aggressive" VHs). An extensive list of treatment modalities is currently available, but the role of techniques such as embolization, radiotherapy, and vertebroplasty as adjuvants to surgery has not yet been elucidated. There exists a need to succinctly summarize the treatments and associated outcomes to guide VH treatment plans. In this review article, a single institution's experience in the management of symptomatic VHs is summarized along with a review of the available literature on their clinical presentation and management options, followed by a proposal of a management algorithm., (Published by Elsevier Inc.)
- Published
- 2023
- Full Text
- View/download PDF
42. Clinical diagnostic and radiographic features of a primary intradural spinal chondrosarcoma in a young adult: illustrative case.
- Author
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Piscopo AJ, Teferi N, Hanson A, Challa M, Smith M, Eschbacher K, and Hitchon P
- Abstract
Background: Mesenchymal chondrosarcoma (MCS) is an aggressive subtype of chondrosarcoma that occurs extremely rarely in the central nervous system. Patients often present with pain or sensorimotor deficits, and resection is considered the gold standard. The role of adjuvant radiation and/or chemotherapy is largely unknown., Observations: A 22-year-old male presented with a 4-month history of progressive back and bilateral leg pain. He underwent imaging workup with magnetic resonance imaging of the lumbar spine and was found to have an intradural, extramedullary, heterogeneously enhancing mass spanning the L4-5 vertebral levels. Intraoperatively, a lobular, partially calcified mass with a ventral dural attachment displacing the nerve roots laterally was observed. The mass was removed en bloc, and the patient later underwent adjuvant radiotherapy, with no evidence of recurrence 2 years following surgery., Lessons: Spinal MCS is extremely rare and often presents with a more aggressive course than conventional chondrosarcoma. Radiological diagnosis is challenging, as the tumor mimics different pathologies. The presence of calcifications, heterogeneous enhancement, and a more rapid clinical course as well as the presence of HEY1::NCOA2 gene fusion, which can be detected by surrogate immunohistochemistry, aids in diagnosis. Resection is the standard of care, and adjuvant radiation may be considered to reduce local recurrence, although further studies are warranted.
- Published
- 2023
- Full Text
- View/download PDF
43. Pediatric brainstem abscess successfully treated with stereotactic aspiration: illustrative case.
- Author
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Teferi N, Chowdhury A, Lee S, Challa M, Weiner L, Auerbach S, Rao M, and Dlouhy BJ
- Abstract
Background: Pediatric brainstem abscesses are rare entities that account for 1% of all brain abscesses and, when diagnosed, constitute a neurosurgical emergency., Observations: A previously healthy 11-year-old male presented with several days of worsening headache, confusion, and ataxia. Brain magnetic resonance imaging (MRI) revealed a midbrain and pons lesion. The patient subsequently had a rapid neurological decline with loss of consciousness and brainstem function. Follow-up MRI revealed significant enlargement of the brainstem lesion with extension into the pons, midbrain, and thalamus, with greater concerns for an abscess rather than a tumor or an inflammatory process. He was taken for an emergent stereotactic aspiration of the abscess, and broad-spectrum antibiotics were initiated. He had neurological improvement, which subsequently declined 5 days later with brain MRI revealing an increase in the brainstem abscess, which required a second stereotactic aspiration. After rehabilitation, he made a significant neurological recovery., Lessons: Pediatric brainstem abscesses are rare pathologies, and a high index of suspicion is needed in patients presenting with a brainstem lesion mimicking tumor but with rapid neurological decline despite no other evidence of infection or infectious/inflammatory markers. Stereotactic aspiration is required for large lesions to target the antibiotic treatment and as an adjunct to broad-spectrum antibiotics.
- Published
- 2023
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- View/download PDF
44. Individual SNOT-22 Items Aid in Differentiating Between Spontaneous Cerebrospinal Fluid Rhinorrhea and Chronic Rhinosinusitis Without Nasal Polyps.
- Author
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Liu MY, Gardner JR, Woodworth BA, Jang DW, Kanaan A, Radabaugh JP, Yao WC, Goros M, Challa M, Grayson JW, Wang Z, and Chen PG
- Subjects
- Humans, Sino-Nasal Outcome Test, Retrospective Studies, Chronic Disease, Facial Pain, Rhinorrhea, Quality of Life, Nasal Polyps diagnosis, Cerebrospinal Fluid Rhinorrhea diagnosis, Nasal Obstruction, Rhinitis complications, Rhinitis diagnosis, Sinusitis complications, Sinusitis diagnosis
- Abstract
Objectives: Spontaneous cerebrospinal fluid (CSF) rhinorrhea is a diagnostic challenge due to its overlapping symptomatology with other sinonasal diseases. The objective of this study was to investigate whether items on the sinonasal outcome test (SNOT)-22 could suggest a diagnosis of spontaneous CSF rhinorrhea versus chronic rhinosinusitis without nasal polyps (CRSsNP)., Methods: A multi-institutional retrospective chart review of patients with spontaneous CSF rhinorrhea and a control group of CRSsNP patients was performed. Individual SNOT-22 scores and domain scores were compared., Results: One hundred fifteen patients were included in both cohorts. Of the patients in the CSF rhinorrhea group, 48% were misdiagnosed as chronic rhinosinusitis (CRS) prior to the correct identification of a CSF leak. On bivariate analysis, the CSF rhinorrhea group scored significantly higher on the SNOT-22 for runny nose ( P < .001) and was more likely to designate this symptom as most important ( P < .001). The CRSsNP group scored significantly higher in nasal blockage ( P < .001), thick nasal discharge ( P < .001), facial pain/pressure ( P < .001), and in the ear/facial ( P < .001) and rhinologic ( P = .003) domains. Multivariable logistic regression revealed that runny nose ( P < .001) was most predictive of spontaneous CSF rhinorrhea while nasal blockage ( P < .001), thick nasal discharge ( P < .001), and facial pain/pressure ( P = .001) were predictive of CRSsNP after adjusting for relevant confounders. No significant difference was observed in total SNOT-22 scores between groups ( P = .676)., Conclusions: Spontaneous CSF rhinorrhea is commonly misdiagnosed as other sinonasal pathologies. However, individual SNOT-22 items can help aid in suggesting a CSF leak. Spontaneous CSF rhinorrhea should be suspected in patients who have high SNOT-22 scores for runny nose and report this symptom as most important, but have lower scores related to the other cardinal symptoms of CRS.
- Published
- 2023
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45. Economic Viability of Penicillin Allergy Testing to Avoid Improper Clindamycin Surgical Prophylaxis.
- Author
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Liu MY, Challa M, McCoul ED, and Chen PG
- Subjects
- Humans, Clindamycin adverse effects, Penicillins adverse effects, Anti-Bacterial Agents adverse effects, Antibiotic Prophylaxis adverse effects, Retrospective Studies, Surgical Wound Infection prevention & control, Drug Hypersensitivity diagnosis, Drug Hypersensitivity etiology, Drug Hypersensitivity prevention & control, Hypersensitivity complications
- Abstract
Objective: Patients mislabeled with a penicillin allergy are often unnecessarily given prophylactic clindamycin. Thus, otolaryngologists may cause harm due to clindamycin's associated risk of Clostridioides difficile infections (CDI) and surgical site infections (SSI). The objective of this study was to determine the economic feasibility of penicillin allergy testing in preventing unnecessary clindamycin use among patients with an unconfirmed penicillin allergy prior to otolaryngologic surgery., Methods: A break-even analysis was performed using the average cost of penicillin allergy testing and a CDI/SSI to calculate the absolute risk reduction (ARR) in baseline CDI/SSI rate due to clindamycin required for penicillin testing to be economically sustainable. The binomial distribution was used to calculate the probability that current penicillin testing can achieve this study's ARR., Results: Preoperative penicillin testing was found to be economically sustainable if it could decrease the baseline CDI rate by an ARR of 1.06% or decrease the baseline SSI rate by an ARR of 1.34%. The probability of penicillin testing achieving these ARRs depended on the baseline CDI and SSI rates. When the CDI rate was at least 5% or the SSI rate was at least 7%, penicillin allergy testing was guaranteed to achieve economic sustainability., Conclusion: In patients mislabeled with a penicillin allergy, preoperative penicillin allergy testing may be an economically sustainable option to prevent the unnecessary use of prophylactic clindamycin during otolaryngologic surgery. Current practice guidelines should be modified to recommend penicillin allergy testing in patients with an unconfirmed allergy prior to surgery., Level of Evidence: NA Laryngoscope, 133:1086-1091, 2023., (© 2022 The American Laryngological, Rhinological and Otological Society, Inc.)
- Published
- 2023
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46. Adsorption efficacy of functionalized Cu-BDC MOFs tethered 2-mercaptobenzimidazole analogue: A comparative study.
- Author
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Challa M, Chinnam S, Rajanna AM, Nandagudi A, Yallur BC, and Adimule V
- Abstract
A novel metal-organic framework [MOFs], and 2-[benzo [ d ]thiazol-2-ylthio)-3-hydroxy acrylaldehyde-Cu-benzene dicarboxylic acid was synthesized by solvothermal method and characterized using p -XRD, FSEM-EDX, TGA, BET, FTIR. The tethered organic linker, 2-[benzo [ d ]thiazol-2-ylthio)-3-hydroxyacrylaldehyde was commonly known as 2-mercaptobenimidazole analogue [2-MBIA]. Analysis of BET disclosed that addition of 2-MBIA to Cu-benzene dicarboxylic acid [Cu-BDC], reduced the crystallite size from 70.0 nm to 65.90 nm, surface area from 17.95 to 17.02 m
2 g-1 and enhances the pore size from 5.84 nm with 0.027 cm3 g-1 pore volume to 8.74 nm with 0.361 cm3 g-1 pore volume. Batch experiments were conducted to optimize pH, adsorbent dosage, and, Congo red (CR) concentration. The adsorption percentage of CR on the novel MOFs was 54%. Adsorption kinetic studies revealed that the uptake adsorption capacity at equilibrium was 184.7 mg/g from pseudo-first-order kinetics which gave a good fit with the experimental data. Intraparticle diffusion model explained the process of the adsorption mechanism: diffusion from the bulk solution onto the porous surface of the adsorbent. Freundlich and Sips models were the best fit models of the several non-linear isotherm models. Temkin isotherm suggested the adsorption of CR on MOFs was of an exothermic nature., Competing Interests: There is no conflict of interest declared by authors., (© 2023 Published by Elsevier Ltd.)- Published
- 2023
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- View/download PDF
47. Editorial Perspective: The mental health impact of school closures during the COVID-19 pandemic.
- Author
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Almeida M, Challa M, Ribeiro M, Harrison AM, and Castro MC
- Subjects
- Adolescent, Child, Humans, Mental Health, SARS-CoV-2, Schools, COVID-19 prevention & control, Pandemics prevention & control
- Abstract
School closures were one of the earlier actions taken as the world tried to contain the COVID-19 outbreak, a decision impacting nearly three-fourths of the learners worldwide. One year into the pandemic, over 200 million students still faced disruptions to their education. Nearing the end of another academic year that has occurred entirely during the pandemic, many schools remained fully or partially closed for in-person education, altering routines and representing potential hardships to the next generation and their families. This article will explore the potential impacts of school closures on children and adolescents related to increased screen time, irregular sleep patterns, less balanced diets, learning difficulties, and changes in social interaction. In addition, we note broader familial difficulties likely accompanying the loss of the mitigating effects of schools and their associated support systems, such as parental stress and work responsibilities, loss of employment, intimate partner violence, child abuse and neglect, and parental substance abuse, which appear to have increased during the pandemic. Considering what is known about the impact from previous natural catastrophes, the populations at risk, and the early but not yet definitive data from the current pandemic, we stress the urgent need for robust data as we prepare for a new academic year in the Northern Hemisphere. Although we currently lack consistent and complete data, signs for concern include a rise in pediatric emergency room visits for mental health and substance use issues in many parts of the world. This paper aims to stimulate a discussion about the potential mental health effects of school closures for children and adolescents in the context of a pandemic., (© 2021 Association for Child and Adolescent Mental Health.)
- Published
- 2022
- Full Text
- View/download PDF
48. Rowell Syndrome with Good Response to Methotrexate.
- Author
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Challa M, Baisya R, and Devarasetti PK
- Published
- 2022
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49. Mediation by Executive Functions in the Associations Between Perceived Stress, Prenatal Distress, Emotional Control, and Dietary Intake in Overweight or Obese Pregnant Women.
- Author
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Chang MW, Tan A, Schaffir J, Wegener DT, Worly B, Strafford K, Sampsell C, Kemper K, Soma L, Rosen M, Ranatunga A, and Challa M
- Abstract
Background: The study explored potential mediation by executive functions (behavioral regulation index [BRI] and metacognition index [MI]) in association between perceived stress, prenatal distress, emotional control, and dietary intake (total calorie, total fat, added sugar, fruits, and vegetables)., Methods: 70 overweight or obese pregnant women completed validated online surveys and two 24-hour dietary recalls. Path analyses were performed., Results: Increased perceived stress was associated with increased BRI both directly (p < 0.001) and indirectly through increased MI (perceived stress to MI: p < 0.001, MI to BRI: p < 0.001). Subsequently, increased BRI was associated with increased total fat intake (p = 0.01). Two-stage mediation was found in the association of prenatal distress with total fat intake. Increased prenatal distress was associated with increased MI (p < 0.001). Higher MI was associated with higher BRI (p < 0.001), and higher BRI was associated with increased total fat intake (p = 0.01)., Conclusions: Future intervention studies for overweight or obese pregnant women might focus on stress management to alleviate perceived stress and prenatal distress or on strategies to boost executive functions, each of which might ultimately help to reduce total fat intake., Competing Interests: 9.Conflicts of Interest The authors declare no conflict of interest. The sponsor has no role in the design, execution, interpretation, or writing of the study.
- Published
- 2022
- Full Text
- View/download PDF
50. Synthesis of hierarchical structured Gd doped α -Sb 2 O 4 as an advanced nanomaterial for high performance energy storage devices.
- Author
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Adimule V, Yallur BC, Challa M, and Joshi RS
- Abstract
Bimetallic oxide nanostructures (NS) of Gd
x : α-Sb2 O4 (x = 5, 8, 10 wt.%) emerged as novel electrode material for batteries as they exhibit large specific capacity and cyclic stability. Crystal structure of Gd: α-Sb2 O4 NS investigated by X-ray diffraction (XRD) patterns and identified as mixed orthorhombic phase. Surface chemical composition, binding energies of the metal oxides and incorporation of Gd into α-Sb2 O4 NS analysed by XPS (X-ray photoelectron spectral) studies. Microstructure analysis reveals that distinctive flower/flake like arrays with agglomeration. Morphology, structure and physical/chemical properties of the resulting nanostructure were analysed by SEM (scanning electron microscopy), SEM-EDX (scanning electron microscopy-energy dispersive X-ray), BET (Brunauer-Emmett-Teller), XPS, UV-Visible and XRD studies. Electrochemical performances of Gdx : α-Sb2 O4 (x = 10 wt.%) in 6 M KOH aqueous solution dipped in three electrode system evaluated by CV (cyclic voltammetry), GCD (galvanostatic charge-discharge) and EIS (electrochemical impedance spectroscopy) measurements. The as-synthesized NS exhibited higher specific capacitance of 958 mAh/g at a current density of 0.15 A/g and excellent cyclic stability with 86.5% capacitive retention after 1000 cycles. Distinctive flower/flake like structure, large surface area, and abundant active sites of Gdx : α-Sb2 O4 NS could be the reason for significant increase in charge transfer and storage. In brief this work offers facile method to synthesize Gdx : α - Sb2 O4 NS are promising electrode materials for potential applications in high performance super capacitor., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors.)- Published
- 2021
- Full Text
- View/download PDF
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