Experimental Study of X-ray Production and Implosion Dynamics of Low-, Mid-, and High-Atomic-Number Materials on University-Scale Z-pinch Machines of Various Architecture

Earlier research with the novel Double Planar Wire Array (DPWA) and Double Planar Foil Liner (DPFL) loads imploded on the high-impedance UNR Zebra Marx bank generator showed them to be excellent radiators of x-rays. This work focuses heavily on implosions of DPWA loads of low- to mid- to high-atomic-number metals and low-atomic-number DPFL loads performed using the low-impedance UM MAIZE Linear Transformer Driver (LTD). The DPWAs consisted of two wire planes of micron-scale sized wires, while the DPFLs consisted of two planes of micron-scale thickness foils. Current from the machine causes the load planes to ablate, creating two sheets of plasma that pinch in the center of the arrays. As the load begins to implode, radiation in a broad range is emitted, and then detected using various diagnostics, such as an absolutely calibrated PCD, filtered Si-diodes, x-ray pinhole cameras, spectrometers, and a fast, visible light camera which captures plasma evolution. In contrast to the Marx bank (which has been in widespread use in pulsed power research for decades), the LTD is a relatively new pulsed power architecture with the theorized potential to be more efficient than the widely used Marx bank generators. However, up to this point, very little is known on how DPWAs and DPFLs implode on LTDs, so it is important to study. Also, by making comparisons to previous implosions of similar load types on the Zebra generator, we can better understand how the changes in machine architecture and current values affect the radiation emission and implosion dynamics. In addition, unlike the Zebra generator, the low-impedance of the MAIZE LTD makes the discharge current highly susceptible to changes in the load inductance. By studying the load inductance throughout the Z-pinching process of DPWAs and DPFLs on the MAIZE LTD, we can better optimize future loads for the potential of reaching higher peak currents, faster current risetimes, and greater x-ray emission. To perform experimental low-current produced plasma research on the UNR main campus, and to test x-ray diagnostics as well as train students, we have developed a hard x-ray source based on a vacuum diode with laser-plasma cathode triggering dubbed “Sparky-HXRS” (or Sparky Hard X-Ray Source). One of the main objectives of this research was to study the hard x-ray characteristic radiation which is believed to be caused by inner-shell ionization of neutral atoms by non-thermal electron beams propagating through the cold thermal plasma. Such hard x-ray characteristic radiation as well as its polarization properties has not yet been studied in detail in pulsed power plasmas. Sparky-HXRS was designed for producing monochromatic x-rays while keeping the production of bremsstrahlung low in comparison. Laser-driven vacuum x-ray diodes have been attractive for the generation of short-duration x-ray pulses in a compact set-up, which can be temporally synchronized with the laser pulse. Such a device can operate with any voltage, and, if operated with the optimal voltage, can provide better monochromatization of a particular radiation range. The device was designed such that any desired metal could be studied by using that material of interest to form the anode. A number of anode materials were studied with varying atomic numbers, including: brass (an alloy of copper and zinc), stainless steel (an alloy of iron and chromium), titanium, and tungsten. The development of the Sparky-HXRS device also included the development of an “open-air” spectropolarimeter, to study the polarization of characteristic x-rays

Embedding and enhancing eAssessment in the leading open source VLE.

Automating the assessment of large numbers of students while providing instant personalised feedback requires a multi-faceted computer-based solution. This paper describes how the long term eAssessment developments in science and technology at the Open University (OU) and mathematics at the University of Birmingham have been brought together in Moodle, highlights key features of these developments and discusses the costs and benefits of engaging with these ever more sophisticated systems

Polymicrobial oral biofilm models: simplifying the complex

Over the past century, numerous studies have used oral biofilm models to investigate growth kinetics, biofilm formation, structure and composition, antimicrobial susceptibility and host–pathogen interactions. In vivo animal models provide useful models of some oral diseases; however, these are expensive and carry vast ethical implications. Oral biofilms grown or maintained in vitro offer a useful platform for certain studies and have the advantages of being inexpensive to establish and easy to reproduce and manipulate. In addition, a wide range of variables can be monitored and adjusted to mimic the dynamic environmental changes at different sites in the oral cavity, such as pH, temperature, salivary and gingival crevicular fluid flow rates, or microbial composition. This review provides a detailed insight for early-career oral science researchers into how the biofilm models used in oral research have progressed and improved over the years, their advantages and disadvantages, and how such systems have contributed to our current understanding of oral disease pathogenesis and aetiology

Interplay of Staphylococcal and Host Proteases Promotes Skin Barrier Disruption in Netherton Syndrome.

Netherton syndrome (NS) is a monogenic skin disease resulting from loss of function of lymphoepithelial Kazal-type-related protease inhibitor (LEKTI-1). In this study we examine if bacteria residing on the skin are influenced by the loss of LEKTI-1 and if interaction between this human gene and resident bacteria contributes to skin disease. Shotgun sequencing of the skin microbiome demonstrates that lesional skin of NS subjects is dominated by Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Isolates of either species from NS subjects are able to induce skin inflammation and barrier damage on mice. These microbes promote skin inflammation in the setting of LEKTI-1 deficiency due to excess proteolytic activity promoted by S. aureus phenol-soluble modulin α as well as increased bacterial proteases staphopain A and B from S. aureus or EcpA from S. epidermidis. These findings demonstrate the critical need for maintaining homeostasis of host and microbial proteases to prevent a human skin disease

A nanocarrier system that potentiates the effect of miconazole within different interkingdom biofilms

Background: Novel and new therapeutic strategies capable of enhancing the efficacy of existing antimicrobials is an attractive proposition to meet the needs of society. Objective: This study aimed to evaluate the potentiating effect of a miconazole (MCZ) nanocarrier system, incorporated with iron oxide nanoparticles (IONPs) and chitosan (CS) (IONPs-CS-MCZ). This was tested on three representative complex interkingdom oral biofilm models (caries, denture and gingivitis). Materials and methods: The planktonic and sessile minimum inhibitory concentrations (MICs) of IONPs-CS-MCZ against different Candida albicans strains were determined, as well as against all represented bacterial species that formed within the three biofilm models. Biofilms were treated for 24 hours with the IONPs-CS nanocarrier system containing MCZ at 64 mg/L, and characterized using a range of bioassays for quantitative and qualitative assessment. Results MIC results generally showed that IONPs-CS-MCZ was more effective than MCZ alone. IONPs-CS-MCZ also promoted reductions in the number of CFUs, biomass and metabolic activity of the representative biofilms, as well as altering biofilm ultrastructure when compared to untreated biofilms. IONPs-CS-MCZ affected the composition and reduced the CFEs for most of the microorganisms present in the three evaluated biofilms. In particular, the proportion of streptococci in the biofilm composition were reduced in all three models, whilst Fusobacterium spp. percentage reduced in the gingivitis and caries models, respectively. Conclusion: In conclusion, the IONPs-CS-MCZ nanocarrier was efficient against three in vitro models of pathogenic oral biofilms, showing potential to possibly interfere in the synergistic interactions among fungal and bacterial cells within polymicrobial consortia

4,7-Dichloro­quinoline

The two mol­ecules in the asymmetric unit of the title compound, C9H5Cl2N, are both essentially planar (r.m.s. deviations for all non-H atoms = 0.014 and 0.026 Å). There are no close C—H⋯Cl contacts

Filling the void: an optimized polymicrobial interkingdom biofilm model for assessing novel antimicrobial agents in endodontic infection

There is a growing realization that endodontic infections are often polymicrobial, and may contain Candida spp. Despite this understanding, the development of new endodontic irrigants and models of pathogenesis remains limited to mono-species biofilm models and is bacterially focused. The purpose of this study was to develop and optimize an interkingdom biofilm model of endodontic infection and use this to test suitable anti-biofilm actives. Biofilms containing Streptococcus gordonii, Fusobacterium nucleatum, Porphyromonas gingivalis, and Candida albicans were established from ontological analysis. Biofilms were optimized in different media and atmospheric conditions, prior to quantification and imaging, and subsequently treated with chlorhexidine, EDTA, and chitosan. These studies demonstrated that either media supplemented with serum were equally optimal for biofilm growth, which were dominated by S. gordonii, followed by C. albicans. Assessment of antimicrobial activity showed significant effectiveness of each antimicrobial, irrespective of serum. Chitosan was most effective (3 log reduction), and preferentially targeted C. albicans in both biofilm treatment and inhibition models. Chitosan was similarly effective at preventing biofilm growth on a dentine substrate. This study has shown that a reproducible and robust complex interkingdom model, which when tested with the antifungal chitosan, supports the notion of C. albicans as a key structural component