An Analysis of the Scintillation Properties of Several Materials for Radiation Detection

The accurate detection and identification of ionizing radiation and radioisotopes is of significant interest to governments, industry and the scientific community, particularly for use in detecting illicit radioactive weapons, among other uses. Of all the methods to detect radiation, scintillation has been a mainstay among handheld or portable detectors owing primarily to its simple equipment requirements. In particular, inorganic crystals and plastic scintillators are two scintillating materials with promising characteristics for use in particle identification. In this work, two promising materials are compared to more common detectors of the same type. The inorganic scintillator SrI2:Eu3% is compared to 2 other inorganic crystals, NaI:Tl and LaBr3:Ce on the basis of its energy resolution. The energy resolution for several gamma-ray energies were measured and SrI2:Eu3% was found to have an energy resolution of (6.7±0.1)% for the 662 keV photopeak. SrI2:Eu3% shows significant promise for use in handheld radiation detectors due to its better energy resolution than NaI:Tl and simpler background than LaBr3:Ce. Also investigated was plastic scintillator EJ-299-33A on the basis of its n/gamma discrimination capabilities. Two sizes of EJ-299-33A, 2” × 1” and 2” × 2” were compared to NE-213 through several different pulse shape discrimination methods. Both sizes of EJ-299-33A were found to have very similar discrimination capability, and were comparable to NE-213. The best discrimination for all detectors was by comparing the PID vs. the pulse height. EJ-299-33A was found to have a figure of merit of 1.03 at energies of about 250 keVee for both sizes. EJ-299-33A shows promise for use in n/gamma discrimination where liquid scintillators are not practical

Teaching Case: Paid Search Wars

This case analyzes the complex interactions between firms in the interrelated areas of search engines and portals after the dot com crash of 2000. Overture, a 1998 start-up, had transformed the online advertising market through the innovation of paid search, in which advertisers bid for top position for search terms. These results were provided to the portals and appeared alongside organic search results when a search was done. But Overture became a victim of its own success as the portals used their audience control to gain a greater share of advertising revenues. Google entered the paid search market in 2002 which ultimately led to Overture losing its independence and becoming a Yahoo subsidiary in 2003. As Google grew rapidly and expanded into other markets Yahoo and MSN attempted without success to counteract its influence. By February 2008 Google had been the clear winner of this rivalry, with Yahoo severely weakened. This culminated in an attempted Microsoft takeover of Yahoo with the main aim of stopping Google, a development Google was determined to prevent. This led to Google cooperating with Yahoo on paid search and Microsoft subsequently withdrawing its bid in May 2008

Mesenchymal stem cells - a promising therapy for Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) constitutes a spectrum of severe acute respiratory failure in response to a variety of inciting stimuli that is the leading cause of death and disability in the critically ill. Despite decades of research, there are no therapies for ARDS, and management remains supportive. A growing understanding of the complexity of the pathophysiology of ARDS, coupled with advances in stem cell biology, has lead to a renewed interest in the therapeutic potential of mesenchymal stem cells for ARDS. Recent evidence suggests that mesenchymal stem cells can modulate the immune response to reduce injury and also increase resistance to infection, while also facilitating regeneration and repair of the injured lung. This unique combination of effects has generated considerable excitement. We review the biological characteristics of mesenchymal stem cells that underlie their therapeutic potential for ARDS. We also summarise existing pre-clinical evidence, evaluate the potential and pitfalls of using mesenchymal stem cells for treatment, and examine the likely future directions for mesenchymal stem cells in ARDS

Clinical Review: Gene-based therapies for ALI/ARDS: where are we now?

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) confer substantial morbidity and mortality, and have no specific therapy. The accessibility of the distal lung epithelium via the airway route, and the relatively transient nature of ALI/ARDS, suggest that the disease may be amenable to gene-based therapies. Ongoing advances in our understanding of the pathophysiology of ALI/ARDS have revealed multiple therapeutic targets for gene-based approaches. Strategies to enhance or restore lung epithelial and/or endothelial cell function, to strengthen lung defense mechanisms against injury, to speed clearance of infection and to enhance the repair process following ALI/ARDS have all demonstrated promise in preclinical models. Despite three decades of gene therapy research, however, the clinical potential for gene-based approaches to lung diseases including ALI/ARDS remains to be realized. Multiple barriers to effective pulmonary gene therapy exist, including the pulmonary architecture, pulmonary defense mechanisms against inhaled particles, the immunogenicity of viral vectors and the poor transfection efficiency of nonviral delivery methods. Deficits remain in our knowledge regarding the optimal molecular targets for gene-based approaches. Encouragingly, recent progress in overcoming these barriers offers hope for the successful translation of gene-based approaches for ALI/ARDS to the clinical setting

Bench-to-bedside review: Carbon dioxide

Carbon dioxide is a waste product of aerobic cellular respiration in all aerobic life forms. PaCO2 represents the balance between the carbon dioxide produced and that eliminated. Hypocapnia remains a common - and generally underappreciated - component of many disease states, including early asthma, high-altitude pulmonary edema, and acute lung injury. Induction of hypocapnia remains a common, if controversial, practice in both adults and children with acute brain injury. In contrast, hypercapnia has traditionally been avoided in order to keep parameters normal. More recently, advances in our understanding of the role of excessive tidal volume has prompted clinicians to use ventilation strategies that result in hypercapnia. Consequently, hypercapnia has become increasingly prevalent in the critically ill patient. Hypercapnia may play a beneficial role in the pathogenesis of inflammation and tissue injury, but may hinder the host response to sepsis and reduce repair. In contrast, hypocapnia may be a pathogenic entity in the setting of critical illness. The present paper reviews the current clinical status of low and high PaCO2 in the critically ill patient, discusses the insights gained to date from studies of carbon dioxide, identifies key concerns regarding hypocapnia and hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury