Bu4N(+) Alkoxide-Initiated/Autocatalytic Addition Reactions with Organotrimethylsilanes.

The use of Me3SiO(-)/Bu4N(+) as a general activator of organotrimethylsilanes for addition reactions has been established. The broad scope of the method offers trimethylsilanes (including acetate, allyl, propargyl, benzyl, dithiane, heteroaryl, and aryl derivatives) as bench-stable organometallics that can be readily utilized as carbanion equivalents for synthesis. Reactions are achieved at rt without the requirement of specialized precautions that are commonplace for other organometallics

Solar photocatalysis for water disinfection: Materials and reactor design

As of 2010, access to clean drinking water is a human right according to UN regulations. Nevertheless, the number of people living in areas without safe drinking water is predicted to increase by three billion by the end of this decade. Several recent cases of E. coli and Cryptosporidium contamination in drinking water are also reported in a number of advanced countries. Therefore ensuring the potability of drinking water is urgent, but highly challenging to both the developing and developed world in the future. A combination of solar disinfection and photocatalysis technology offers real possibilities for removing lethal pathogenic microroganisms from drinking water. The time taken for the conventional SODIS process can be greatly reduced by semiconductor (e.g. TiO2, ZnO, nano-heterojunctions) based photocatalysis. This review addresses the fundamental reaction mechanism, advances in materials synthesis and selection and recent developments in the reactor design for solar energy driven photocatalysis using titanium dioxide. The major advantage of using photo-reactors is that they enhance disinfection by increasing photon flux into the photocatalyst. Other major factors affecting such efficiency of solar-based photocatalysis such as the illuminated volume/total volume ratio, catalyst load and flow rate, are discussed in detail. The significance of using immobilised catalysts over the catalyst powder in slurries is also highlighted. It is noted that, despite encouraging early field studies, the commercialisation and mass production of solar photocatalysis systems remains highly challenging. Recommendations for future directions for addressing issues such as mass transfer, requirement of a standard test method, photo-reactors design and visible light absorption by TiO2 coatings are also discussed

Continuous Flow Bioconjugations of NIR-AZA Fluorophores via Strained Alkyne Cycloadditions with Intra-chip Fluorogenic Monitoring

The importance of bioconjugation reactions continues to grow as the need for cell specific targeting and dual therapeutic plus diagnostic medical applications increase. This necessitates new bioconjugation chemistries, synthetic and analytical methods. With this goal, continuous flow bioconjugations were readily achieved with short residence times for strained alkyne substituted carbohydrate and peptide biomolecules in reaction with azide and tetrazine substituted fluorophores. The catalyst and reagent-free inverse electron demand tetrazine cycloadditions proved more favourable than the azide 1,3-dipolar cycloadditions. The use of a fluorogenic tetrazine fluorophore in a glass channelled reactor chip allowed for intra-chip reaction monitoring by recording fluorescence intensities at various positions throughout the chip. As the Diels-Alder reactions proceeded through the chip, the fluorescence intensity increased accordingly in real-time. This novel approach to continuous flow bioconjugation reaction with monitoring may offer advantages over post-chip analysis

NIR fluorophores clinically assessed for fluorescence guided surgery

The term “fluorescence” was first proposed nearly two centuries ago, yet its application in Medicine has a relatively brief history of only 70 years. Nowadays, as fluorescence was gradually approaching into more medicine studies, fluorescence image-guided surgery has become the new arena for this technology. It allows surgeons to real-time visualize the target structure intraoperatively to increase the efficacy of surgical tissue resection and meanwhile avoid unnecessary radical treatment during open surgery, laparoscopy, thoracoscopy, or endoscopes. In this review, we introduce the concept of near-infrared fluorescence imaging for cancer surgery, review the clinical trial literature to date, outline the key issues pertaining to imaging system and contrast agent optimization, discuss limitations and leverage, and provide a framework for making the technology available for the routine care of cancer patients in the near future

Potential for Release of Pulmonary Toxic Ketene from Vaping Pyrolysis of Vitamin E Acetate

The Centers for Disease Control and Prevention has recently reported an increasing number of clinically reported cases of lung injury following use of e-cigarette/vaping products. The cause(s) of this growing epidemic of vaping associated pulmonary injury remain unidentified, though vitamin E acetate has been recently identified as one possible causative agent (see Nature 574, 303 (2019). A combined analytical, theoretical and experimental study has shown that the vaping of vitamin E acetate has the potential to produce exceptionally toxic ketene gas, which may be a contributing factor to the upsurge in lung injuries associated with using some vaping products.</p

Fluorogenic NIR-Probes Based on 1,2,4,5-Tetrazine Substituted BF2-Azadipyrromethenes

A series of 1,2,4,5-tetrazine integrated near infrared (NIR) fluorophores based on the BF2 azadipyrromethene (NIR-AZA) class has been synthesised and their ability to modulate emission from low to high in response to Diels-Alder cycloaditions has been assessed. Substituents on the tetrazine component of the probe (Cl, OMe, p-NO2C6H4O) were seen to strongly influence quantum yields, fluorescence enhancement factors, and rates of cycloadditions. Cycloadditions between tetrazine-NIR-AZA constructs and a strained alkyne substrate were seen to be highly efficient in organic or aqueous solutions and in gels with high fluorescence enhancements of up to 48-fold observed. Real-time demonstration of the cycloaddition mediated fluorogenic property was achieved by imaging the “turn-on” reaction within a continous flow microreactor. Preliminary evidence indicates that excited state quenching involves a photoinduced electron transfer

Azadipyrromethenes: from traditional dye chemistry to leading edge applications.

Azadipyrromethenes were first described over 70 years ago as blue pigments, but now are rapidly emerging as a compound class with highly desirable near infrared photophysical properties. Since the turn of the century several routes to azadipyrromethenes have been developed and numerous post-synthesis derivatizations have allowed for their exploitation in both biological and material sciences. The relative ease of access to specifically designed derivatives is now allowing their use in multiple technological formats from real-time fluorescence imaging, to solar energy materials, to optoelectronic devices and many more. In this review we have highlighted the synthetic component of this story as it is the ability to generate the designer azadipyrromethene that opens the door to exciting applications

A compact sideband-separating (2SB) arrangement using a turnstile

Important requirements of a millimetre-wave heterodyne receiver for radio astronomy are that it can detect dual-linear polarisation and retain both upper and lower sidebands. One such arrangement, referred to as a sideband-separating (2SB) layout, uses a 90\ub0 phase shift on either the LO or signal path before mixing, and the upper and lower sidebands are separated into unique IF outputs once orthogonally re-combined. There is continuing interest to build arrays of heterodyne receivers and part of the challenge is to fit all of the receiver components within a given volume. To realise dual-linear polarisation and 2SB within receiver arrays, a new, more compact approach must be taken. Integrating a turnstile as the signal splitter reduces overall layout space and provides excellent polarisation isolation.Peer reviewed: YesNRC publication: Ye

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

Supervised exercise (SE) in patients with type 2 diabetes improves oxygen uptake kinetics at the onset of exercise. Maintenance of these improvements, however, has not been examined when supervision is removed. We explored if potential improvements in oxygen uptake kinetics following a 12-week SE that combined aerobic and resistance training were maintained after a subsequent 12-week unsupervised exercise (UE). The involvement of cardiac output (CO) in these improvements was also tested. Nineteen volunteers with type 2 diabetes were recruited. Oxygen uptake kinetics and CO (inert gas rebreathing) responses to constant-load cycling at 50% ventilatory threshold (VT), 80% VT, and mid-point between VT and peak workload (50% &Delta;) were examined at baseline (on 2 occasions) and following each 12-week training period. Participants decided to exercise at a local gymnasium during the UE. Thirteen subjects completed all the interventions. The time constant of phase 2 of oxygen uptake was significantly faster (p &lt; 0.05) post-SE and post-UE compared with baseline at 50% VT (17.3 &plusmn; 10.7 s and 17.5 &plusmn; 5.9 s vs. 29.9 &plusmn; 10.7 s), 80% VT (18.9 &plusmn; 4.7 and 20.9 &plusmn; 8.4 vs. 34.3 &plusmn; 12.7s), and 50% &Delta; (20.4 &plusmn; 8.2 s and 20.2 &plusmn; 6.0 s vs. 27.6 &plusmn; 3.7 s). SE also induced faster heart rate kinetics at all 3 intensities and a larger increase in CO at 30 s in relation to 240 s at 80% VT; and these responses were maintained post-UE. Unsupervised exercise maintained benefits in oxygen uptake kinetics obtained during a supervised exercise in subjects with diabetes, and these benefits were associated with a faster dynamic response of heart rate after training.<br /

Calculus in Context

Designing the curriculum We believe that calculus can be for students what it was for Euler and the Bernoullis: a language and a tool for exploring the whole fabric of science. We also believe that much of the mathematical depth and vitality of calculus lies in connections to other sciences. The mathematical questions that arise are compelling in part because the answers matter to other disciplines. We began our work with a clean slate, not by asking what parts of the traditional course to include or discard. Our starting points are thus our summary of what calculus is really about. Our curricular goals are what we aim to convey about the subject in the course. Our functional goals describe the attitudes and behaviors we hope our students will adopt in using calculus to approach scientific and mathematical questions. Starting Points Calculus is fundamentally a way of dealing with functional relationships that occur in scientific and mathematical contexts. The techniques of calculus must be subordinate to an overall view of the questions that give rise to these relationships. Technology radically enlarges the range of questions we can explore and the ways we can answer them. Computers and graphing calculators are much more than tools for teaching the traditional calculus. The concept of a dynamical system is central to science. Therefore, differential equations belong at the center of calculus, and technology makes this possible at the introductory level. The process of successive approximation is a key tool of calculus, even when the outcome of the process--the limit--cannot be explicitly given in closed form. Curricular Goals Develop calculus in the context of scientific and mathematical questions. Treat systems of differential equations as fundamental objects of study. Construct and analyze mathematical models. Use the method of successive approximations to define and solve problems. Develop geometric visualization with hand-drawn and computer graphics. Give numerical methods a more central role. Functional Goals Encourage collaborative work. Enable students to use calculus as a language and a tool. Make students comfortable tackling large, messy, ill-defined problems. Foster an experimental attitude towards mathematics. Help students appreciate the value of approximate solutions. Teach students that understanding grows out of working on problems. Impact of Technology Differential equations can now be solved numerically, so they can take their rightful place in the introductory calculus course. The ability to handle data and perform many computations makes exploring messy, real-world problems possible. Since we can now deal with credible models, the role of modelling becomes much more central to the subject. The text illustrates how we have pursued the curricular goals. Each goal is addressed within the first chapter which begins with questions about describing and analyzing the spread of a contagious disease. A model is built: a model which is actually a system of coupled non-linear differential equations. We then begin a numerical exploration on those equations, and the door is opened to a solution by successive approximations. Our implementation of the functional goals is also evident. The text has many more words than the traditional calculus book--it is a book to be read. The exercises make unusual demands on students. Most are not just variants of examples that have been worked in the text. In fact, the text has rather few template\u27\u27 examples. Shifts in Emphasis It will also become apparent to you that the text reflects substantial shifts in emphasis in comparison to the traditional course. Here are some of the most striking: How the emphasis shifts: increase: concepts, geometry, graphs, brute force, numerical solutions decrease: techniques, algebra, formulas, elegance, closed-form solutions Since we all value elegance, let us explain what we mean by brute force. Euler\u27s method is a good example. It is a general method of wide applicability. Of course when we use it to solve a differential equation like y\u27(t) = t, we are using a sledgehammer to crack a peanut. But at least the sledgehammer works. Moreover, it works with coconuts (like y\u27 = y(1 - y/10)), and it will even knock down a house (like y\u27 = cos2(t)). Students also see the elegant special methods that can be invoked to solve y\u27 = t and y\u27 = y(1 - y/10) (separation of variables and partial fractions are discussed in chapter 11), but they understand that they are fortunate indeed when a real problem will succumb to such methods.https://scholarworks.smith.edu/textbooks/1001/thumbnail.jp