Spacecraft detumbling using movable telescoping appendages

The dynamics of detumbling a randomly spinning spacecraft using externally mounted, movable telescoping appendages were studied both analytically and numerically. Two types of telescoping appendages are considered: where an end mass is mounted at the end of an (assumed) massless boom; and where the appendage is assumed to consist of a uniformly distributed homogeneous mass throughout its length. From an application of Liapunov's second method, boom extension maneuvers were determined to approach either of two desired final states: close to a zero inertial angular velocity state, and a final spin rate about only one of the principal axes. Recovery dynamics are evaluated analytically for the case of symmetrical deployment. Numerical examination of other asymmetrical cases verifies the practicality of using movable appendages to recover a randomly tumbling spacecraft

The dynamics and optimal control of spinning spacecraft and movable telescoping appendages, part A

The problem of optimal control with a minimum time criterion as applied to a single boom system for achieving two axis control is discussed. The special case where the initial conditions are such that the system can be driven to the equilibrium state with only a single switching maneuver in the bang-bang optimal sequence is analyzed. The system responses are presented. Application of the linear regulator problem for the optimal control of the telescoping system is extended to consider the effects of measurement and plant noises. The noise uncertainties are included with an application of the estimator - Kalman filter problem. Different schemes for measuring the components of the angular velocity are considered. Analytical results are obtained for special cases, and numerical results are presented for the general case

The dynamics and control of large flexible space structures. Part A: Discrete model and modal control

Attitude control techniques for the pointing and stabilization of very large, inherently flexible spacecraft systems were investigated. The attitude dynamics and control of a long, homogeneous flexible beam whose center of mass is assumed to follow a circular orbit was analyzed. First order effects of gravity gradient were included. A mathematical model which describes the system rotations and deflections within the orbital plane was developed by treating the beam as a number of discretized mass particles connected by massless, elastic structural elements. The uncontrolled dynamics of the system are simulated and, in addition, the effects of the control devices were considered. The concept of distributed modal control, which provides a means for controlling a system mode independently of all other modes, was examined. The effect of varying the number of modes in the model as well as the number and location of the control devices were also considered

The dynamics of spin stabilized spacecraft with movable appendages, part 1

The motion and stability of spin stabilized spacecraft with movable external appendages are treated both analytically and numerically. The two basic types of appendages considered are: (1) a telescoping type of varying length and (2) a hinged type of fixed length whose orientation with respect to the main part of the spacecraft can vary. Two classes of telescoping appendages are considered: (a) where an end mass is mounted at the end of an (assumed) massless boom; and (b) where the appendage is assumed to consist of a uniformly distributed homogeneous mass throughout its length. For the telescoping system Eulerian equations of motion are developed. During all deployment sequences it is assumed that the transverse component of angular momentum is much smaller than the component along the major spin axis. Closed form analytical solutions for the time response of the transverse components of angular velocities are obtained when the spacecraft hub has a nearly spherical mass distribution

COMPUTATIONAL ANALYSIS OF FEASIBILITY AND UTILITY OF DIRECT-ADHESION POLYMER-TO-METAL HYBRID TECHNOLOGIES FOR USE IN LOAD BEARING BODY-IN-WHITE AUTOMOTIVE COMPONENTS

Traditionally, metals and plastics are fierce competitors in many automotive engineering applications. This paradigm is gradually being abolished as the polymer-metal-hybrid (PMH) technologies, developed over the last decade, are finding ways to take full advantage of the two classes of materials by combining them into a singular component/sub-assembly. By employing one of the several patented PMH technologies, automotive original equipment manufacturers (OEMs) have succeeded in engaging flexible assembly strategies, decreasing capital expenditures and reducing labor required for vehicle manufacture. The basic concept utilized in all PMH technologies is based on the fact that while an open-channel thin-wall sheet-metal component can readily buckle under compressive load, with very little lateral support, provided by a thin-wall rib-like injection-molded plastic subcomponent, the buckling resistance (and the stiffness) of the component can be greatly increased (while the accompanied weight increase is relatively small). In the present work, the potential of direct-adhesion PMH technologies for use in load-bearing structural automotive components is explored computationally. Within the direct adhesion PMH technology, load transfer between stamped sheet-metal and injection-molded rib-like plastic subcomponent is accomplished through a variety of nanometer-to-micron scale chemical and mechanical phenomena which enable direct adhesion between the two materials. Multi-disciplinary computations are carried out ranging from: (a) computational investigation of the sheet-metal stamping process including determination of the residual stresses and the extent of stamped-component warping; (b) computational fluid mechanics of the filling, packing and cooling stages of the injection-molding process including determination of flow-induced fiber orientation in the molded plastic and the extent of residual stresses and warping in the injection-molded sub-component: and (c) structural-mechanics computational investigation of the effect of injection-molded component residual stresses and warping on their ability to withstand thermal loading encountered in the paint shop and mechanical in-service loading. The results obtained revealed that a minimal level of the polymer-to-metal adhesion strength (5-10MPa) must be attained in order for the direct-adhesion PMH technologies to be a viable alternative in the load-bearing body-in-white (BIW) components. In the present work, also various PMH approaches used to promote direct (adhesive-free) adhesion between metal and injection-molded thermoplastics are reviewed and critiqued. The approaches are categorized as: (a) micro-scale polymer-to-metal mechanical interlocking; (b) in-coil or stamped-part pre-coating for enhanced adhesion; and (c) chemical modifications of the injection-molded thermoplastics for enhanced polymer-to-metal adhesion. For each of these approaches their suitability for use in load-bearing BIW components is discussed. In particular, the compatibility of these approaches with the BIW manufacturing process chain (i.e. (pre-coated) metal component stamping, BIW construction via different joining technologies, BIW pre-treated and painting operations) is presented. It has been found that while considerable amount of research has been done in the PMH direct-adhesion area, many aspects of these technologies which are critical from the standpoint of their use in the BIW structural applications have not been addressed (or addressed properly). Among the PMH technologies identified, the one based on micro-scale mechanical interlocking between the injection-molded thermoplastic polymer and stamped-metal structural component was found to be most promising. Lastly, the suitability and the potential of various polymer-powder spraying technologies for coating metal stampings and, thus, for enhancing the polymer-to-metal adhesion strength in direct-adhesion PMH load-bearing automotive-component applications is considered. The suitability of the spraying technologies is assessed with respect to a need for metal-stamping surface preparation/treatment, their ability to deposit the polymeric material without significant material degradation, the ability to selectively overcoat the metal-stamping, the resulting magnitude of the polymer-to-metal adhesion strength, durability of the polymer/metal bond with respect to prolonged exposure to high-temperature/high-humidity and mechanical/thermal fatigue service conditions, and compatibility with the automotive BIW manufacturing process chain. The analysis revealed that while each of the spraying technologies has some limitations, the cold-gas dynamic-spray process appears to be the leading candidate technology for the indicated applications

A STUDY ON THE AWARENESS AND ATTITUDE TOWARDS PHARMACOVIGILANCE AND ADVERSE DRUG REACTION REPORTING AMONG NURSING STUDENTS IN A PRIVATE UNIVERSITY, MALAYSIA

Objective: This study was conducted to evaluate the knowledge and attitude towards pharmacovigilance and adverse drug reactions reporting among the nursing students in a private university, Malaysia. Methods: The survey was carried out using a pre-validated questionnaire that included demographics details and 29 survey items to evaluate the participant's knowledge and perception on adverse drug reactions and pharmacovigilance. The questionnaire was distributed to the participants (n=32) pre-final and final year nursing students after their informed consent. Results: The study results found that, there was no significant difference noticed between the mean knowledge score on ADRs reporting and pharmacovigilance of pre-final year and final year students (p>0.05). The overall mean score on knowledge was found to be 12.31. The study also observed that mean score on attitude in pre-final year and final year students were 13.24 and 16.00 respectively. There was no significant difference observed between the mean score on the perception of pre-final year and final year students (p>0.05). The overall mean score for perception on ADRs reporting and pharmacovigilance was found to be 15.06. Conclusion: The results show that nursing students who participated in the study were only moderately aware of pharmacovigilance and adverse drug reaction reporting. However, they had expressed the positive attitude towards pharmacovigilance and ADRs reporting. As future health care professionals, they are expected to have sound knowledge and positive attitude towards pharmacovigilance activities. Their knowledge and attitude would exert a strong influence on ADRs reporting

DEVELOPMENT AND VALIDATION OF RP-HPLC METHOD FOR THE ESTIMATION OF ESCITALOPRAM OXALATE AND FLUPENTIXOL DIHYDROCHLORIDE IN COMBINED DOSAGE FORM AND PLASMA

Objective: The objective of the study was to develop a simple and rapid chromatographic method for quantification of escitalopram oxalate and flupentixol dihydrochloride in combined dosage form and plasma. Methods: The separation was achieved with a sun fire C8 [150×4.6 mm] 3.5 µm column with an isocratic mobile phase containing a mixture of potassium dihydrogen orthophosphate buffer: methanol: acetonitrile [30:60:10 v/v/v] pH adjusted to 11. The flow rate of the mobile phase was 1.5 ml/min with a Photodiode array [PDA] detection at 230 nm. Results: The HPLC method was developed and validated with respective linearity, accuracy, and precision, detection of limit, robustness, and specificity. The precision of the results stated as the relative standard deviation was below 2 %. The calibration curve was linear over a concentration range from 10-50 µg/ml for escitalopram oxalate and 1-5 µg/ml for flupentixol dihydrochloride with a correlation co-efficient 0.994 and 0.977 respectively. The accuracy of the method was demonstrated at levels in the range of 100 % and 120 % of the specification limit. The recovery of escitalopram oxalate and flupentixol dihydrochloride was found to be in the range of 90 % to 88 %, respectively. The lowest detection limits were found to be 2 µg/ml for escitalopram oxalate and 0.1 µg/ml for flupentixol dihydrochloride. The lowest quantification limits were found to be 5 µg/ml of escitalopram oxalate and 0.5 µg/ml of flupentixol dihydrochloride. Conclusion: The developed method was validated for linearity, accuracy, precision, the limit of detection and quantification, specificity. The method was applied successfully for the determination of escitalopram oxalate and flupentixol dihydrochloride in the combined dosage form and plasma

BUCCAL PENETRATION ENHANCERS-AN OVERVIEW

Over the last decade, there has been a particular interest in delivering drugs in buccal mucosa and aiming to increase bioavailability of varied controlled drug delivery systems (CDDS), mucoadhesion (the capability of a object to adhere to mucous membranes) occupies a unique position. Buccal administration of API provides a convenient route of administration for both systemic and local actions. It provides direct entry into the systemic circulation thus avoiding the hepatic first-pass effect and degradation in the gastrointestinal tract. However permeability of oral mucosa is limiting factor which relatively low compared to intestinal mucosa and the skin. When permeability differences between various organs of the oral region are taken into consideration, buccal membrane found to be more permeable. In order to deliver wider classes of drugs across the buccal mucosa, the barrier potential of mucosa must be reduced. This requisite has forced the study of buccal penetration enhancers that will overcome the permeability barrier of the buccal mucosa. Numerous compounds have been evaluated for penetration enhancing activity, including bile salts, surfactants, fatty acids and derivatives, ethanol, cyclodextrins and chitosan etc. The purpose of this review is to identify the structural and chemical nature of the permeability barrier the buccal mucosa, to clarify the mechanisms of action of buccal penetration enhancers. &nbsp

FORMULATION AND EVALUATION OF NEVIRAPINE MUCOADHESIVE MICROSPHERES

Objective: The objective of the present research was to formulate and evaluate HPMC K4M, HPMC K100, and Carbopol 940 Mucoadhesive microspheres in combination with sodium alginate for controlling release of Nevirapine. Methods: Nevirapine microspheres were prepared by an Ionotropic gelation method using aluminium sulfate as a cross linking agent. The developed Nevirapine microspheres were characterized for Micromeritic properties, morphology, drug entrapment efficiency, in vitro wash off test, in vitro drug release, and interaction studies (Fourier transfer infrared spectroscopy (FTIR) & Differential scanning calorimetry (DSC). Results: The Nevirapine mucoadhesive microspheres were free-flowing and discrete. The mean particle size ranged from 705.21±2.00 to 935.45±2.07 μm and the entrapment efficiencies ranged from 63.50 to 96.42 %. All the nevirapine microsphere batches showed good in vitro mucoadhesive property ranging from 03-68 % in the in-vitro mucoadhesive test after 8 h. FT-IR studies indicated the lack of nevirapine-polymer interactions in the nevirapine microspheres formulation. There were no compatibility issues and the crystallinity of nevirapine was found to be reduced in prepared mucoadhesive microspheres, which were confirmed by DSC and X-ray diffraction studies (XRD). Among different formulations, the nevirapine microspheres of batch F8 had shown the optimum percent drug entrapment and the controlled release of the nevirapine for about 12 h (98.65%). The Release pattern of nevirapine from microspheres of batch F8 followed the Korsmeyer- peppas and zero-order release kinetic model. The value of ‘n' was found to be 1.402, which indicates that the drug release was followed super case II transport type. Stability studies were carried out for F8 formulation at 4 °C/Ambient, 25±2 °C/60±5 %, 40±2 °C/75±5 % RH revealed that the drug entrapment and mucoadhesive behavior were within permissible limits. Conclusion: The results obtained in this present work demonstrate the potential use of HPMC K100 polymer for preparation of controlled delivery nevirapine mucoadhesive microspheres and prolonged residence at the absorption site.Â

Joint preservation surgery: a priority to be thought of in selective hip osteoarthritis

Femoroacetabular impingement (FAI) is one of the causes of hip arthritis. If FAI diagnosed earlier and treated properly, arthritis of hip and eventual total hip replacement (THR) can be potentially avoided. We report 48 yr male who presented with left hip severe pain, limp, restricted movements and unable do daily day activities. He is diagnosed to have pincer type of lesion in the acetabular rim and we did arthroscopic excision of the protruding fragment. The patient now has a pain free joint and able to squat and sit cross leg. His pre-operative oxford hip score was 30 which improved to 54.