Numerical Study of Scan Speed Selection and Kerf Depth Prediction in Silicon Laser Machining

In recent times, lasers have gained popularity in machining applications. This trend has been due to the various unique properties that lasers posses. These properties include the ease of manipulation, and the ability to focus the beam to a small spot. Laser machining offers a better alternative to traditional machining since it does cause tool wear, and no mechanical cutting force is required. In this research, effects of the Nd:YAG laser scan speed on kerf depth is investigated. A numerical model was developed using finite element analysis method to investigate the effects using COMSOLR. ImageJR software was used for image analysis and generation of kerf depth predictions. The results of this study show that increasing the laser scan speed led to a decrease in the kerf depth. Various scan speeds can also be optimally selected for different laser application. Cutting quality is improved if scan speeds of the laser are chosen properly. Keywords: Scan speed, kerf depth, laser

Col V siRNA Engineered Tenocytes for Tendon Tissue Engineering

The presence of uniformly small collagen fibrils in tendon repair is believed to play a major role in suboptimal tendon healing. Collagen V is significantly elevated in healing tendons and plays an important role in fibrillogenesis. The objective of this study was to investigate the effect of a particular chain of collagen V on the fibrillogenesis of Sprague-Dawley rat tenocytes, as well as the efficacy of Col V siRNA engineered tenocytes for tendon tissue engineering. RNA interference gene therapy and a scaffold free tissue engineered tendon model were employed. The results showed that scaffold free tissue engineered tendon had tissue-specific tendon structure. Down regulation of collagen V α1 or α2 chains by siRNAs (Col5α1 siRNA, Col5α2 siRNA) had different effects on collagen I and decorin gene expressions. Col5α1 siRNA treated tenocytes had smaller collagen fibrils with abnormal morphology; while those Col5α2 siRNA treated tenocytes had the same morphology as normal tenocytes. Furthermore, it was found that tendons formed by coculture of Col5α1 siRNA treated tenocytes with normal tenocytes at a proper ratio had larger collagen fibrils and relative normal contour. Conclusively, it was demonstrated that Col V siRNA engineered tenocytes improved tendon tissue regeneration. And an optimal level of collagen V is vital in regulating collagen fibrillogenesis. This may provide a basis for future development of novel cellular- and molecular biology-based therapeutics for tendon diseases

Influence of hypoxia on the domiciliation of Mesenchymal Stem Cells after infusion into rats: possibilities of targeting pulmonary artery remodeling via cells therapies?

BACKGROUND: Bone marrow (BM) cells are promising tools for vascular therapies. Here, we focused on the possibility of targeting the hypoxia-induced pulmonary artery hypertension remodeling with systemic delivery of BM-derived mesenchymal stem cells (MSCs) into non-irradiated rats. METHODS: Six-week-old Wistar rats were exposed to 3-week chronic hypoxia leading to pulmonary artery wall remodeling. Domiciliation of adhesive BM-derived CD45(- )CD73(+ )CD90(+ )MSCs was first studied after a single intravenous infusion of Indium-111-labeled MSCs followed by whole body scintigraphies and autoradiographies of different harvested organs. In a second set of experiments, enhanced-GFP labeling allowed to observe distribution at later times using sequential infusions during the 3-week hypoxia exposure. RESULTS: A 30% pulmonary retention was observed by scintigraphies and no differences were observed in the global repartition between hypoxic and control groups. Intrapulmonary radioactivity repartition was homogenous in both groups, as shown by autoradiographies. BM-derived GFP-labeled MSCs were observed with a global repartition in liver, in spleen, in lung parenchyma and rarely in the adventitial layer of remodeled vessels. Furthermore this global repartition was not modified by hypoxia. Interestingly, these cells displayed in vivo bone marrow homing, proving a preservation of their viability and function. Bone marrow homing of GFP-labeled MSCs was increased in the hypoxic group. CONCLUSION: Adhesive BM-derived CD45(- )CD73(+ )CD90(+ )MSCs are not integrated in the pulmonary arteries remodeled media after repeated intravenous infusions in contrast to previously described in systemic vascular remodeling or with endothelial progenitor cells infusions

Implementing and Evaluating Community Health Worker-Led Cardiovascular Disease Risk Screening Intervention in Sub-Saharan Africa Communities: A Participatory Implementation Research Protocol.

The increasing burden of non-communicable diseases (NCDs), particularly cardiovascular diseases (CVD) in low- and middle-income countries (LMICs) poses a considerable threat to public health. Community-driven CVD risk screening, referral and follow-up of those at high CVDs risk is essential to supporting early identification, treatment and secondary prevention of cardiovascular events such as stroke and myocardial infarction. This protocol describes a multi-country study that aims to implement and evaluate a community health worker (CHW)-led CVD risk screening programme to enhance referral linkages within the local primary care systems in sub-Saharan Africa (SSA), using a participatory implementation science approach. The study builds upon a prior community-driven multicentre study conducted by the Collaboration for Evidence-based Health Care and Public Health in Africa (CEBHA+). This is a participatory implementation research. The study will leverage on the CVD risk citizen science pilot studies conducted in the four selected CEBHA+ project countries (viz. Ethiopia, Rwanda, Malawi, and South Africa). Through planned engagements with communities and health system stakeholders, CHWs and lay health worker volunteers will be recruited and trained to screen and identify persons that are at high risk of CVD, provide referral services, and follow-up at designated community health clinics. In each country, we will use a multi-stage random sampling to select and then screen 1000 study participants aged 35-70 years from two communities (one rural and one urban). Screening will be done using a simple validated non-laboratory-based CVD risk assessment mobile application. The RE-AIM model will be used in evaluating the project implementation outcomes, including reach, fidelity, adoption and perceived effectiveness. Developing the capacities of CHWs and lay health worker volunteers in SSA to support population-based, non-invasive population-based CVD risk prevention has the potential to impact on early identification, treatment and secondary prevention of CVDs in often under-resourced communities. Using a participatory research approach to implementing mobile phone-based CHW-led CVD risk screening, referral and follow-up in SSA will provide the evidence needed to determine the effectiveness of CVD risk screening and the potential for scaling up in the wider region

Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally

Toll-Like Receptor 3 and Suppressor of Cytokine Signaling Proteins Regulate CXCR4 and CXCR7 Expression in Bone Marrow-Derived Human Multipotent Stromal Cells

The use of bone marrow-derived human multipotent stromal cells (hMSC) in cell-based therapies has dramatically increased in recent years, as researchers have exploited the ability of these cells to migrate to sites of tissue injury, inflammation, and tumors. Our group established that hMSC respond to "danger" signals--by-products of damaged, infected or inflamed tissues--via activation of Toll-like receptors (TLRs). However, little is known regarding downstream signaling mediated by TLRs in hMSC.We demonstrate that TLR3 stimulation activates a Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 1 pathway, and increases expression of suppressor of cytokine signaling (SOCS) 1 and SOCS3 in hMSC. Our studies suggest that each of these SOCS plays a distinct role in negatively regulating TLR3 and JAK/STAT signaling. TLR3-mediated interferon regulatory factor 1 (IRF1) expression was inhibited by SOCS3 overexpression in hMSC while SOCS1 overexpression reduced STAT1 activation. Furthermore, our study is the first to demonstrate that when TLR3 is activated in hMSC, expression of CXCR4 and CXCR7 is downregulated. SOCS3 overexpression inhibited internalization of both CXCR4 and CXCR7 following TLR3 stimulation. In contrast, SOCS1 overexpression only inhibited CXCR7 internalization.These results demonstrate that SOCS1 and SOCS3 each play a functionally distinct role in modulating TLR3, JAK/STAT, and CXCR4/CXCR7 signaling in hMSC and shed further light on the way hMSC respond to danger signals

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis

Assessing The Accuracy Of The Jm-102 Transcutaneous Bilirubin Measurement In Dark Skin Jaundiced Neonates: Case Of University Teaching Hospital, Rwanda

Background: Clinical assessment of neonatal jaundice is inaccurate and results in a significant number of blood tests in otherwise well babies. The number of these blood tests could be reduced, with benefit to the neonates and potential cost savings by using a noninvasive transcutaneous bilirubinometer. Objective: The aim of our study was to evaluate the accuracy of one of the birubinometer JM-102(Minolta/Hill-Rom Air-Shields ® JM-102), in dark skin term and preterm neonates old less than two weeks compared to the gold standard which is the measurement of serum bilirubin (SBR) and to identify the most informative value of transcutaneous bilirubinometer (TcB) in terms of sensitivity and specificity. Methods: The study included 275 jaundiced neonates who were less than 14 days and consulted neonatology unit of University teaching hospital during the study period. Neonates with severe conditions (hypothermia, respiratory distress, cardiovascular disorders, and neurological disorders) and/or with previous history of phototherapy were excluded from the study. On these 275 newborns, the Minolta/Hill-Rom Air-Shields ® JM-102 was used to measure the transcutaneous bilirubin and SRB sampling was performed within 30 minutes. All newborns were black skin. Results: The correlation of the gold standard and the measurements of the TcB Minolta/Hill-Rom Air-Shields ® JM-102 was 74.5 %. Comparing the gold standard with measurements of the TcB Minolta/Hill-Rom Air-Shields ® JM-102, we estimated the area under the Receiver Operating Curve(ROC) to be 0.887 classified as good and a p value of < 0.001 suggesting that the TcB measurement is far better than guessing. Conclusion: The correlation between TcB measurement and the serum bilirubin measurement was good for the population studied. The TcB measurement using the Minolta/Hill-Rom Air Shields ® JM-102 was found to be useful in detecting infant with hyperbilirubinaemia in dark skin jaundiced neonates.The Minolta JM-102 device could be used as a screening instrument, leading to the avoidance of invasive blood samplings for term and preterm neonates. TcB measurements with the JM-102 bilirubinometer should obviate the need for serum bilirubin levels in dark skin jaundiced newborns, although serum bilirubin measurements are still required when treatment with phototherapy or exchange transfusion is being considered.Introduction: L’évaluation visuelle de l’ictère néonatal est imprécise et conduit aux prélèvements sanguins inutiles pour dosage de la bilirubine chez les nouveau-nés qui de part ailleurs sont en bon état général. Le nombre et le coût de ces prélèvements pourraient être réduits par l’utilisation non invasive du bilirubinomètre transcutané. Objectif: Le but de notre étude était d’évaluer l’utilité du bilirubinomètre JM-102(Minolta/Hill-Rom Air-Shields ® JM-102) chez les nouveau-nés à peau foncée âgés de moins de deux semaines de vie présentant un ictère néonatal. Les mesures fournis par le bilirubinomètre ont été comparés au gold standard qui est le dosage sérique de la bilirubine. Méthodes: L’étude a enrôlé 241 nouveau-nés âgés de moins de 2 semaines présentant un ictère néonatal et 34 nouveau-nés non ictériques. Les nouveau-nés qui étaient en mauvais état général (hypothermique, en détresse respiratoire, présentant des troubles hémodynamiques ou des troubles neurologiques) ou qui avaient été sous photothérapie ont été exclus de l’étude. Le bilirubinomètre transcutané JM-102(Minolta/Hill-Rom Air-Protections ® JM-102) a été appliqué au niveau frontal et sternal et le sang pour dosage de la bilirubine sérique a été prélevé dans les 30 minutes suivant la mesure transcutanée. Tous les nouveau-nés enrôlés dans l’étude étaient à peau foncée. Résultats: La corrélation des résultats fournis par le bilirubinomètre transcutané et ceux obtenus par le dosage sérique de la bilirubine était de 74,5%. L’aire en dessous de la courbe ROC (Receiver Operating Cuve) était de 0,887 avec une valeur p <0,001 suggérant que l’évaluation de l’ictère néonatal par le bilirubinomètre transcutané était de loin meilleur que l’évaluation visuelle. Conclusion: La corrélation entre les résultats fournis par le bilirubinometre transcutané JM 102 et le dosage de la bilirubine sérique était bonne sur la population étudiée. Le bilirubinomètre Minolta JM-102 pourrait être utilisé pour identifier les nouveau-nés ictériques chez lesquels le dosage de la bilirubine sérique devrait être fait en vue d’une photothérapie ou exsanguino-transfusion éventuelle