Response Spectrum Analysis of Printed Circuit Boards Subjected to Shock Loads

AbstractA spacecraft consists of a number of electronic packages to meet the functional requirements. An electronic package is generally an assembly of printed circuit boards placed in a mechanical housing. A number of electronic components are mounted on the printed circuit board (PCB). A spacecraft experiences various types of loads during its launch such as vibration, acoustic and shock loads. Prediction of response for printed circuit boards due to shock loads is important for mechanical design and reliability of electronic packages. The modeling and analysis of printed circuit boards is required for accurate prediction of response due to shock loads. The validated finite element model of the PCB can be adopted to perform response spectrum analysis. Shock response spectrum analysis of printed circuit boards subjected to a half-sine pulse excitation is carried out using finite element method. The objective of this paper is to predict the shock response spectrum of a printed circuit board due to launch environment. The analysis results are validated by conducting experimental tests of PCB

Management challenges arising from a traumatic 360 degree cyclodialysis cleft

We describe the case of a 28-year-old naval officer who attended the ophthalmology service following blunt ocular trauma to the left eye. Clinical examination revealed a shallow anterior chamber, hypotony, and a 360° cyclodialysis cleft. We discuss the management options in this case, with an overview of the current literature

A simulation tool for better management of retinal services

Background: Advances in the management of retinal diseases have been fast-paced as new treatments become available, resulting in increasing numbers of patients receiving treatment in hospital retinal services. These patients require frequent and long-term follow-up and repeated treatments, resulting in increased pressure on clinical workloads. Due to limited clinic capacity, many National Health Service (NHS) clinics are failing to maintain recommended follow-up intervals for patients receiving care. As such, clear and robust, long term retinal service models are required to assess and respond to the needs of local populations, both currently and in the future. Methods: A discrete event simulation (DES) tool was developed to facilitate the improvement of retinal services by identifying efficiencies and cost savings within the pathway of care. For a mid-size hospital in England serving a population of over 500,000, we used 36 months of patient level data in conjunction with statistical forecasting and simulation to predict the impact of making changes within the service. Results: A simulation of increased demand and a potential solution of the 'Treat and Extend' (T&E) regimen which is reported to result in better outcomes, in combination with virtual clinics which improve quality, effectiveness and productivity and thus increase capacity is presented. Without the virtual clinic, where T&E is implemented along with the current service, we notice a sharp increase in the number of follow-ups, number of Anti-VEGF injections, and utilisation of resources. In the case of combining T&E with virtual clinics, there is a negligible (almost 0%) impact on utilisation of resources. Conclusions: Expansion of services to accommodate increasing number of patients seen and treated in retinal services is feasible with service re-organisation. It is inevitable that some form of initial investment is required to implement service expansion through T&E and virtual clinics. However, modelling with DES indicates that such investment is outweighed by cost reductions in the long term as more patients receive optimal treatment and retain vision with better outcomes. The model also shows that the service will experience an average of 10% increase in surplus capacity.Peer reviewedFinal Published versio

Development of an innovative interlocking load bearing hollow block system in Malaysia

The paper describes the development of a new interlocking hollow block masonry system appropriate for load bearing masonry wall construction. The developed system is an alternative to the traditional bonded masonry system where the blocks in the wall are integrated through mortar layers. In the system developed, the blocks are stacked on one another and three-dimensional interlocking protrusions are provided in the blocks to integrate the blocks into walls. This paper includes the background, concept and procedure used to develop an efficient interlocking hollow block system, which may be used in the construction of load bearing walls. Twenty-one different block models have been investigated and analysed with respect to weight, bearing and shear areas, shape, ease of production, ability to accommodate vertical and horizontal reinforcing stabilising ties and efficiency of the interlocking mechanism under imposed loads. The blocks, developed under the name ‘PUTRA BLOCK’, have been used to construct a single-storey house at Universiti Putra Malaysia. The system provides a fast, easy and an accurate building system

Evaluation of automated multiclass fluid segmentation in optical coherence tomography images using the Pegasus fluid segmentation algorithms

Purpose: To evaluate the performance of the Pegasus-OCT (Visulytix Ltd) multiclass automated fluid segmentation algorithms on independent spectral domain optical coherence tomography data sets. Methods: The Pegasus automated fluid segmentation algorithms were applied to three data sets with edematous pathology, comprising 750, 600, and 110 b-scans, respectively. Intraretinal fluid (IRF), sub-retinal fluid (SRF), and pigment epithelial detachment (PED) were automatically segmented by Pegasus-OCT for each b-scan where ground truth from data set owners was available. Detection performance was assessed by calculating sensitivities and specificities, while Dice coefficients were used to assess agreement between the segmentation methods. Results: For two data sets, IRF detection yielded promising sensitivities (0.98 and 0.94, respectively) and specificities (1.00 and 0.98) but less consistent agreement with the ground truth (dice coefficients 0.81 and 0.59); likewise, SRF detection showed high sensitivity (0.86 and 0.98) and specificity (0.83 and 0.89) but less consistent agreement (0.59 and 0.78). PED detection on the first data set showed moderate agreement (0.66) with high sensitivity (0.97) and specificity (0.98). IRF detection in a third data set yielded less favorable agreement (0.46–0.57) and sensitivity (0.59–0.68), attributed to image quality and ground truth grader discordance. Conclusions: The Pegasus automated fluid segmentation algorithms were able to detect IRF, SRF, and PED in SD-OCT b-scans acquired across multiple independent data sets. Dice coefficients and sensitivity and specificity values indicate the potential for application to automated detection and monitoring of retinal diseases such as age-related macular degeneration and diabetic macular edema. Translational Relevance: The potential of Pegasus-OCT for automated fluid quantification and differentiation of IRF, SRF, and PED in OCT images has application to both clinical practice and research

Purification and characterization of platelet aggregation inhibitors from snake venoms

Proteins that inhibit glycoprotein (GP) IIb/IIIa mediated platelet aggregation have been purified from the venom of two snake species. A small platelet aggregation inhibitor (pl.AI), multisquamatin (Mr=5,700), was purified from Echis multisquamatus venom by hydrophobic interaction HPLC and two steps on C18 reverse phase HPLC. A larger pl.AI, contortrostatin (Mr=15,000), was purified by a similar HPLC procedure from the venom of Agkistrodon contortrix contortrix. Both pl.AIs inhibit ADP-induced human, canine and rabbit platelet aggregation using platelet rich plasma (PRP). Multisquamatin has an IC50 of 97 nM, 281 nM and 333 nM for human, canine and rabbit PRP, respectively. Contortrostatin has an IC50 of 49 nM, 120 nM and 1,150 nM for human, canine and rabbit PRP, respectively. In a competitive binding assay using 125I-7E3 (a monoclonal antibody to GPIIb/IIIa that inhibits platelet aggregation) both contortrostatin and multisquamatin demonstrated GPIIb/IIIa specific binding to human and canine platelets. The IC50 for contortrostatin displacement of 7E3 binding to human and canine GPIIb/IIIa is 27 nM and 16 nM, respectively and for multisquamatin it is 3 nM and 63 nM, respectively. Our results indicate that both pl.AIs inhibit platelet aggregation by binding with high affinity to GPIIb/IIIa.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31863/1/0000813.pd

Titanium elastic nails versus spica cast in pediatric femoral shaft fractures:A systematic review and meta-analysis of 1012 patients

Background: There is a general consensus on the management of femoral fractures in children younger than two years and adolescents older than sixteen years. The best treatment for patients younger than sixteen years of age is still debatable. Titanium Elastic Nails (TEN), is widely used with some evidence, nonetheless, we undertook a systematic meta-analysis to assess the efficacy of TEN compared to Spica cast for the management of femoral shaft fracture in children aged between 2 to 16 years old. Methods: A computer literature search of PubMed, Scopus, Web of Science, CINAHL and Cochrane Central was conducted using relevant keywords. We included clinical trials and observational studies that compared TEN versus Spica cast; Records were screened for eligible studies and data were extracted and synthesized using Review Manager version 5.3 for Windows. Our search found 573 unique articles. After screening the abstract and relevant full text, 12 studies with a total of 1012 patients were suitable for the final analysis. Results: In terms terms of union (in weeks), the reported effect sizes favoured the TEN group in two included studies only. Moreover, the overall standardized mean difference in sagittal (SMD -0.48, 95% CI [-0.70 to -0.26], P<0.001) and coronal angulations (SMD -0.66, 95% CI [-1.00 to -0.31], P<0.001) favored TEN fixation in management of femoral fractures younger than 16 years. The reported length of hospital stay was not consistent across studies. The overall risk ratio of malalignment (RR=0.39, 95% CI [0.27 to 0.57], P<0.001) favored the TEN as well as walking independently. Based on our analysis, TEN treatment is superior to traction and hip spica for femoral fractures in patients younger than 16 years old. Conclusion: Based on our analysis we recommend the use of TEN fixation in management of pediatric femoral fractures in patients younger than 16 years