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Organic semiconductors, including graphitic carbon nitride (g-C3N4, CN), represent an important class of materials for the development of novel antimicrobial or biomedical technologies. Of principal interest is the ability of these materials to catalyze the reduction of elemental oxygen to generate reactive oxygen species (ROS), including hydrogen peroxide (H2O2). Here, we describe the fabrication of photoactive van der Waals heterojunctions incorporating 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) and CN. The composite heterojunction systems were characterized by a combination of physical (TEM, SEM, pXRD), spectroscopic (FT-IR, XPS, DRUV, photoluminescence, TCSPC) and kinetic experiments. Electronic interactions between the two components of the heterojunction increase the rate of photochemical production of H2O2 from elemental oxygen by 410%, relative to samples of pure CN. Mechanistic analysis reveals that interaction of NTCDA with the surface of CN modifies the mechanism of H2O2 formation in the heterojunction photocatalysts. The photochemical production of H2O2 by irradiation of the most active heterojunction composition is sufficient to reduce the viability of E. coli O157:H7, S. aureus and Ps. aeruginosa PAO1 by 99%. Importantly, H2O2 production by the NTCDA/CN heterojunctions suppresses Ps. aeruginosa biofilm formation, even at light exposure doses that had a lesser impact on overall planktonic cell growth.

Free-standing, composite hydrogels containing the visible-light responsive metal-free semiconductor graphitic carbon nitride (g-C3N4) as an integral component have been fabricated by direct casting...

In this manuscript, we describe the fabrication of photoactive biocidal or sporicidal films from urea-derived graphitic carbon nitride (u-g-C3N4). Co-deposited films of u-g-C3N4 and Escherichia coli O157:H7 (IC50 = 14.1 ± 0.2 mJ) or Staphylococcus aureus (methicillin resistant IC50 = 33.5 ± 0.2 mJ, methicillin sensitive IC50 = 42.7 ± 0.5 mJ) demonstrated significantly enhanced bactericidal behavior upon administration of visible radiation (400 nm ≤ λ ≤ 426 nm). In all cases, complete eradication of the microbial sample was realized upon administration of 100 mJ of visible radiation, while no antimicrobial activity was observed for non-irradiated samples. In contrast, Bacillus anthracis endospores were more resistant to u-g-C3N4 mediated killing with only a ca. 25% reduction in spore viability when treated with a 200 mJ dose of visible radiation. Characterization of u-g-C3N4 reveals that the improved activity results from enhancements of both the surface area and reduction potential of the material’s conduction band edge, coupled with fast injection of charge carriers into localized states and a decline in radiative recombination events. The results of this study demonstrate that g-C3N4-based materials offer a viable scaffold for the development of new, visible light driven technologies for controlling potentially pathogenic microorganisms.

Photoactive films derived from nanostructured samples of metal-free, intermediate band gap semiconductor graphitic carbon nitride (ns-g-C3N4) have been synthesized and characterized for their particle properties and antimicrobial activity. Physical characterization reveals that these materials are composed of discrete nanoparticles whose dimensions range from 200 nm to 700 nm. Investigation of the photochemical reactivity of ns-g-C3N4 using coumarin-3-carboxylic acid (3-CCA) indicates that this material produces reactive oxygen species (ROS) under visible radiation. When irradiated with 0.31 J visible light, ns-g-C3N4-based materials reduced the viability of both Gram-negative Escherichia coli O157:H7 and Gram-positive Staphylococcus aureus by approximately 50%. Nearly complete inactivation of both strains of microorganisms was achieved upon administration of a 0.62 J dose of visible radiation. Importantly, no biocidal activity was observed for non-irradiated samples, indicating that the g-C3N4-derived films are not inherently toxic in the absence of visible light. The results of this study suggest that materials and, by extention, films and coatings derived from g-C3N4 may present a novel route for controlling pathogenic microorganisms on surfaces in the environment, and could be useful in reducing incidents of hospital-acquired infections.

Background Borrelia burgdorferi causes Lyme disease, the most common tick-borne illness in the United States. The Center for Disease Control and Prevention estimates that the occurrence of Lyme disease in the U.S. has now reached approximately 300,000 cases annually. Early stage Borrelia burgdorferi infections are generally treatable with oral antibiotics, but late stage disease is more difficult to treat and more likely to lead to post-treatment Lyme disease syndrome. Methods Here we examine three unique 5′-methylthioadenosine/S-adenosylhomocysteine (MTA/SAH) nucleosidases (MTNs or MTANs, EC 3.2.2.9) responsible for salvage of adenine and methionine in B. burgdorferi and explore their potential as antibiotic targets to treat Lyme disease. Recombinant Borrelia MTNs were expressed and purified from E. coli. The enzymes were extensively characterized for activity, specificity, and inhibition using a UV spectrophotometric assay. In vitro antibiotic activities of MTN inhibitors were assessed using a bioluminescent BacTiter-Glo™ assay. Results The three Borrelia MTNs showed unique activities against the native substrates MTA, SAH, and 5′-deoxyadenosine. Analysis of substrate analogs revealed that specific activity rapidly dropped as the length of the 5′-alkylthio substitution increased. Non-hydrolysable nucleoside transition state analogs demonstrated sub-nanomolar enzyme inhibition constants. Lastly, two late stage transition state analogs exerted in vitro IC50 values of 0.3–0.4 μg/mL against cultured B. burgdorferi cells. Conclusion B. burgdorferi is unusual in that it expresses three distinct MTNs (cytoplasmic, membrane bound, and secreted) that are effectively inactivated by nucleoside analogs. General significance The Borrelia MTNs appear to be promising targets for developing new antibiotics to treat Lyme disease.

This essay analyzes a representative sample of travel and immigration texts set in Upper Canada, from John Howison (1821) to Samuel Strickland (1853), for the struggle played out within them between images of republicanism and monarchism. It identifies a pervasive fear in these writers of the contamination of the colony with principles and behaviour entirely contrary to its British origins. The construction of the colony these texts attempt was rife with the possibilities of transculturation through their delivery of the discourse of republicanism to the British reading public. In 1832 Henry Clay, a resilient and popular American political leader who had backed the War of 1812, told his supporters in one of several nearly - successful presidential campaigns that the "eyes of all civilized nations are intensely gazing upon us; and it may truly be asserted that the fate of Liberty throughout the World mainly depends upon the maintenance of American liberty."(f.1) No nation was more mesmerized than England, divided between those who revered and those who abhorred the American example. Five years after Clay's speech, Anna Jameson, in one of the best - known travel books on Upper Canada, said of the colony that the very first elements out of which our social system was framed, were repugnance and contempt for the new institutions of the United States, and a dislike to the people of that country ... [T]he slightest tinge of democratic, or even liberal principles in politics, was for a long time a sufficient impeachment of the loyalty, a stain upon the personal character, of those who held them.(f.2) Mrs. Jameson was in the colony at the behest of her husband, its attorney general, and these claims are coloured by time she spent at the seat of power, associating with the administrative elite and observing colonial politics. Her implication that this "long time" has passed does not take into account the rebellion of 1837, which took place just after she left and which renewed and exacerbated the negative and reactive tendencies in colonial politics. Ten years later, John Richardson, now remembered for Wacousta, in his account of Eight Years in Canada describes the moderate reformers in the first union Executive Council as "extreme Radicals" belonging to "the rebel party" (192, 191); they earn this description due to their "Wat Tyler - like demand[s]" for control of patronage and responsible government (191). To us, for whom democracy is a sacrosanct if seldom examined concept, the idea that mere association with it might stain one's character seems outrageous. In the texts analyzed in this article, however, the "democratic, or even liberal principles" portrayed as American and republican are everywhere decried, or discussed in terms so cautious as palpably to project a fear of contamination. Raymond Williams reminds us that democracy "only came into common English use at the time of the American and French Revolutions" and that "Democrats ... were seen, commonly, as dangerous and subversive mob agitators" (xiv). The representation of Americans, of republicanism and of democracy in British travel and immigration narratives about Upper Canada engage their authors, often consciously, in a struggle to shape the future. Setting aside the more material embodiments of that struggle, what follows will deal with how it plays out in these texts, with the images of republicanism versus monarchy that they circulate in England through the colonial relay. Throughout the 1830's, governors and lieutenant - governors were convinced they were fighting a decisive battle against American - style republicanism and democracy, the triumph of which would lead to the end of monarchy and the loss of the colonies" - so writes an American scholar of Canadian history who compares the second quarter of the nineteenth century in Upper Canada "to the critical periods between 1689 and 1720 in England and 1763 and 1789 in the . …

The Faculty of Accident and Emergency Medicine was inaugurated on 2 November 1993. The new council decided that it would like a logo or badge to signify its identity and to adorn such items as headed notepaper and the president's badge of office. As registrar I was instructed to approach the College of Arms for letters-patent granting the faculty its own coat of arms. Because of the multidisciplinary nature of accident and emergency medicine, the faculty is an intercollegiate one based on six royal colleges. The faculty has flourished, it has a steadily increasing membership, and the faculty board's examination committee holds regular examinations for fellowship of the faculty twice a year. The first step was to approach the College of Arms in London and the duty herald, who in our case was William Hunt, Portcullis Pursuivant of Arms. He led me through the detailed process of acquiring our armorial bearings. We submitted the articles of constitution of the faculty to Portcullis, who submitted them to the Kings of Arms. The faculty was then given permission to petition the Earl Marshal for armorial bearings. Portcullis had made it clear that the smaller the committee designing the coat of arms the better. He favoured a committee of one. In the event we formed a small subcommittee of three. Figure 1 shows the principal elements of an achievement of arms, in this case those of the Worshipful …

The increasing need for unattended sensor networks drives individual sensor development, signal processing for network management, and communication technology. The application space is becoming more complex, with requirements for sensor networks in force protection; surveillance of large expanses of rugged terrain; and monitoring complex urban areas. Individual sensors exhibit excellent performance and include a wide variety of sensing modes, such as acoustic, electro-optical imaging, seismic, and radio frequency devices. These sensors continue to shrink with packaging, while applications continue to demand more of the sensor technology. Although single imaging arrays, which are available in spectral bands from the visible through the infrared, can be integrated into packages size as small as a cubic inch, the information from a single sensor is not sufficient to meet requirements for day/night, all-weather operation. This has driven the need for integration of multiple sensors into the compact packages intended for an individual sensor. A major step toward addressing the need for more effective sensor technology for unattended sensor networks is being taken through development of Vertically Integrated Sensor Array (VISA) technology. This technology, currently being developed for imaging sensors, builds multiple layers of signal processing at each pixel in the sensor array. Processing power is dramatically increased, allowing the integration of multiple sensors in small compact packages. This paper reviews the VISA approach to imaging sensors and describes applications for unattended sensors.

The gap between industry and education should be a cause of concern to both sides. Employers too often see the gap as the failure of the education system to meet the needs of employment. This narrow view, however, is both arrogant and lacking in an appreciation of the full extent of the problem. It takes two sides to create a gap and in this case industry must accept its share of blame for the poor co‐operation and understanding which exists between education and the world of work.

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The Working Mathematics Group, a voluntary body which works on a shoestring budget mostly raised its own efforts, has a proud record of achievement. Yet it looks like moving into a crisis condition towards the end of this year for lack of financial support. While this is happening the MSC is proposing to invade the field of preparing open learning materials by some sort of bureaucratic system to be paid for out of public funds. In this journal, in our Phoenix Series, we argue that what is required is the reverse of this situation: we need to harness local effort, and voluntary effort, especially when it happens also to be expert effort, in the service of the community — a feature which WMG illustrates to perfection — and move away from organising everything from the centre by highly‐paid career bureaucrats in the manner of the MSC and the Ministries. Now read the inside story from the point of view of the WMG. One lesson is that the disbursement of funds from the public purse to the various agents working to restore the country's prosperity is not really co‐ordinated by any part of the system: one Ministry seems not to know what the others are doing in areas of mutual interest and responsibility. Another lesson is that surely voluntary bodies, with their economical way of working, their ability to address themselves to real problems and their capacity to draw on a corps of dedicated workers giving their services free, should be protected from being driven out of business by the civil service empire builders. (Editor)