Quartz and silica are common materials, and their dissolution is of significant interest to a wide range of scientists. The kinetics of the dissolution of quartz and silica have been measured ...extensively, yet no clear theory of dissolution is available. A novel theory of dissolution and crystallization has recently been proposed that envisages the removal of material from the surface to form ions in solution leaving behind a charged surface vacancy. These vacancies create a potential difference across the Stern layer that accelerates or retards the removal of ions. In this way, the surface potential difference is caused by and influences the rate of the removal of ions. From this theory, a model of quartz dissolution is derived that predicts the observed orders of reaction. This prediction of the orders of reaction fits a data set consisting of 285 experiments. The model also describes the effect of Na+, K+, and Li+ ions, as well as the effect of heavy water. A significant component of the model is its ability to describe the zeta potential of the quartz–water interface. The model successfully predicts a transient period at the beginning of the reaction when the rate could either increase or decrease.
Superconducting quantum bits Clarke, John; Wilhelm, Frank K
Nature (London),
06/2008, Letnik:
453, Številka:
7198
Journal Article
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Superconducting circuits are macroscopic in size but have generic quantum properties such as quantized energy levels, superposition of states, and entanglement, all of which are more commonly ...associated with atoms. Superconducting quantum bits (qubits) form the key component of these circuits. Their quantum state is manipulated by using electromagnetic pulses to control the magnetic flux, the electric charge or the phase difference across a Josephson junction (a device with nonlinear inductance and no energy dissipation). As such, superconducting qubits are not only of considerable fundamental interest but also might ultimately form the primitive building blocks of quantum computers.
A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic ...features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis.
This paper investigates the drivers and inhibitors of Internet privacy concern. Applying the Multidimensional Development Theory to the online environment, we identify the important factors under ...four dimensions—i.e., environmental, individual, information management, and interaction management. We tested our model using data from an online survey of 2417 individuals in Hong Kong. The results show that the factors under all four dimensions are significant in the formation of Internet privacy concern. Specifically, familiarity with government legislation, Internet knowledge, benefit of information disclosure, privacy protection, and social presence reduce Internet privacy concern, while individuals’ previous privacy invasion experience, risk avoidance personality, and sensitivity of information requested by websites increase Internet privacy concern. We conducted an analysis of unobserved heterogeneity to confirm the significance of these factors. A follow-up moderation analysis shows that the individual factors (i.e., previous privacy invasion experience, risk avoidance personality, and Internet knowledge) moderate the effects of the information management factor (i.e., information sensitivity) and the interaction management factors (i.e., privacy protection and social presence). The findings provide an integrated understanding of the formation of Internet privacy concern.
This paper discusses the value of context in theory development in information systems (IS) research. We examine how prior research has incorporated context in theorizing and develop a framework to ...classify existing approaches to contextualization. In addition, we expound on a decomposition approach to contextualization and put forth a set of guidelines for developing context-specific models. We illustrate the application of the guidelines by constructing and comparing various context-specific variations of the technology acceptance model (TAM)-i.e., the decomposed TAM that incorporates interaction effects between context-specific factors, the extended TAM with context-specific antecedents, and the integrated TAM that incorporates mediated moderation and moderated mediation effects of context-specific factors. We tested the models on 972 individuals in two technology usage contexts: a digital library and an agile Web portal. The results show that the decomposed TAM provides a better understanding of the contexts by revealing the direct and interaction effects of context-specific factors on behavioral intention that are not mediated by the TAM constructs of perceived usefulness and perceived ease of use. This work contributes to the ongoing discussion about the importance of context in theory development and provides guidance for context-specific theorizing in IS research.
Within the last two decades, quantum technologies (QT) have made tremendous progress, moving from Nobel Prize award-winning experiments on quantum physics (1997: Chu, Cohen-Tanoudji, Phillips; 2001: ...Cornell, Ketterle, Wieman; 2005: Hall, Hänsch-, Glauber; 2012: Haroche, Wineland) into a cross-disciplinary field of applied research. Technologies are being developed now that explicitly address individual quantum states and make use of the 'strange' quantum properties, such as superposition and entanglement. The field comprises four domains: quantum communication, where individual or entangled photons are used to transmit data in a provably secure way; quantum simulation, where well-controlled quantum systems are used to reproduce the behaviour of other, less accessible quantum systems; quantum computation, which employs quantum effects to dramatically speed up certain calculations, such as number factoring; and quantum sensing and metrology, where the high sensitivity of coherent quantum systems to external perturbations is exploited to enhance the performance of measurements of physical quantities. In Europe, the QT community has profited from several EC funded coordination projects, which, among other things, have coordinated the creation of a 150-page QT Roadmap (http://qurope.eu/h2020/qtflagship/roadmap2016). This article presents an updated summary of this roadmap.
Prehospital blood product transfusion in trauma care remains controversial due to poor-quality evidence and cost. Sequential expansion of blood transfusion capability after 2012 to deployed military ...medical evacuation (MEDEVAC) units enabled a concurrent cohort study to focus on the timing as well as the location of the initial transfusion.
To examine the association of prehospital transfusion and time to initial transfusion with injury survival.
Retrospective cohort study of US military combat casualties in Afghanistan between April 1, 2012, and August 7, 2015. Eligible patients were rescued alive by MEDEVAC from point of injury with either (1) a traumatic limb amputation at or above the knee or elbow or (2) shock defined as a systolic blood pressure of less than 90 mm Hg or a heart rate greater than 120 beats per minute.
Initiation of prehospital transfusion and time from MEDEVAC rescue to first transfusion, regardless of location (ie, prior to or during hospitalization). Transfusion recipients were compared with nonrecipients (unexposed) for whom transfusion was delayed or not given.
Mortality at 24 hours and 30 days after MEDEVAC rescue were coprimary outcomes. To balance injury severity, nonrecipients of prehospital transfusion were frequency matched to recipients by mechanism of injury, prehospital shock, severity of limb amputation, head injury, and torso hemorrhage. Cox regression was stratified by matched groups and also adjusted for age, injury year, transport team, tourniquet use, and time to MEDEVAC rescue.
Of 502 patients (median age, 25 years interquartile range, 22 to 29 years; 98% male), 3 of 55 prehospital transfusion recipients (5%) and 85 of 447 nonrecipients (19%) died within 24 hours of MEDEVAC rescue (between-group difference, -14% 95% CI, -21% to -6%; P = .01). By day 30, 6 recipients (11%) and 102 nonrecipients (23%) died (between-group difference, -12% 95% CI, -21% to -2%; P = .04). For the 386 patients without missing covariate data among the 400 patients within the matched groups, the adjusted hazard ratio for mortality associated with prehospital transfusion was 0.26 (95% CI, 0.08 to 0.84, P = .02) over 24 hours (3 deaths among 54 recipients vs 67 deaths among 332 matched nonrecipients) and 0.39 (95% CI, 0.16 to 0.92, P = .03) over 30 days (6 vs 76 deaths, respectively). Time to initial transfusion, regardless of location (prehospital or during hospitalization), was associated with reduced 24-hour mortality only up to 15 minutes after MEDEVAC rescue (median, 36 minutes after injury; adjusted hazard ratio, 0.17 95% CI, 0.04 to 0.73, P = .02; there were 2 deaths among 62 recipients vs 68 deaths among 324 delayed transfusion recipients or nonrecipients).
Among medically evacuated US military combat causalities in Afghanistan, blood product transfusion prehospital or within minutes of injury was associated with greater 24-hour and 30-day survival than delayed transfusion or no transfusion. The findings support prehospital transfusion in this setting.
Twenty years ago, the original Tactical Combat Casualty Care (TCCC) article was published in this journal. Since TCCC is essentially a set of best-practice prehospital trauma care guidelines ...customized for use on the battlefield, the presence of a journal with a specific focus on military medicine was a profound benefit to the initial presentation of TCCC to the U.S. Military.
In the two ensuing decades, which included the longest continuous period of armed conflict in our nation's history, TCCC steadily evolved as the prehospital trauma care evidence base was augmented and as feedback from user medics, corpsmen, and pararescuemen was obtained.
TCCC has taken a leadership role in advocating for battlefield trauma care advances such as the aggressive use of tourniquets and hemostatic dressings to control life-threatening external hemorrhage; improved fluid resuscitation techniques for casualties in hemorrhagic shock; increased emphasis on airway positioning and surgical airways to manage the traumatized airway; faster, safer, and more effective battlefield analgesia; the increased use of intraosseous vascular access when needed; battlefield antibiotics; and combining good medicine with good small-unit tactics. With the continuing assistance of Military Medicine, these advances and the evidence base that supports them have been presented to TCCC stakeholders.
Now-20 years later-TCCC has been documented to produce unprecedented decreases in preventable combat death in military units that have trained all of their members in TCCC. As a result of this proven success, TCCC has become the standard for battlefield trauma care in the U.S. military and for the militaries of many of our allied nations. Committee on TCCC members and the Joint Trauma System also work closely with civilian trauma colleagues through initiatives such as the Hartford Consensus, the White House Stop the Bleed campaign, and the development of National Association of Emergency Medical Technicians TCCC-based courses to ensure that advances in prehospital trauma care pioneered by the military on the battlefield are translated into civilian practice on the streets of America. Active shooter incidents, terrorist bombings, and the day-to-day trauma that results from motor vehicle accidents and criminal violence create the potential for many additional lives to be saved in the civilian sector. Along with the other components of the Department of Defense's Joint Trauma System, the Committee on TCCC, and the TCCC Working Group have been recognized as a national resource and will continue to advocate for advances in best-practice battlefield trauma care as opportunities to improve are identified.
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