Development of a Novel Lateral-Flow Assay to Detect Yeast Nucleic Acid Sequences

As demand for food increases, rapid testing methods are becoming increasingly important. In the past few years, yogurt has become popular. Yeast species are the most common spoilage organism, costing consumers and food companies money. A novel lateral flow assay has been developed to detect yeast oligonucleotide sequences. Gold nanoparticles were used as the standard reporter and fluorescent nanoparticles were developed as the novel reporter. The fluorescent nanoparticles were ruthenium-doped silica nanoparticles synthesized using the modified Stöber method. Visual analysis of assays using standard reporters showed the limit of detection to be 10 femtomoles of target sequence. Analysis of the fluorescent nanoparticles using a plate reader showed the limit of detection to be 0.027 femtomoles. The fluorescent reporter’s limit of detection is 1000 fold lower due to a sophisticated, more sensitive analysis method. Gold nanoparticles are appropriate for presence or absence testing, but fluorescent nanoparticles are best for obtaining quantitative data with low detection limits. Pathogens have been used as biological warfare for centuries. A brief review of common biowarfare agents is included. Yersinia pestis, the causative agent of the Plague, and Bacillus anthracis, the causative agent of Anthrax, are the focus. Additional work using gold nanoparticles as reporter in a sandwich assay is also included. The novel dye covered reporter was compared to the control, which was a single dye molecule linked to the reporter sequence. Repeated testing showed the novel reporter had a lower limit of detection and higher sensitivity due to increased ability to bind target

Inversion and gain in hydrogenic ion levels induced by photoionization pumping

If a low-Z plasma is subjected to ionizing radiation, stationary inversions on hydrogenic ion level populations occur. The plasma conditions and pumping requirements to achieve gain on the Lyman-alpha and Balmer-alpha lines are investigated by means of a collisional-radiative model. The calculations are carried out for two cases: first, for the case in which the electron temperature is determined solely by radiative cooling, and second, for the case in which additional electron cooling is provided. In the first case, measurable gain on the Balmer-alpha line is found, although the Lyman-alpha transition remains uninverted. In the second case, the Balmer-alpha gain is dramatically enhanced, and sizable Lyman-alpha gain is predicted

Picosecond imaging of low-density plasmas by electron deflectometry

We have imaged optical-field ionized plasmas with electron densities as low as 1013 cm−3 on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons

From Graphene constrictions to single carbon chains

We present an atomic-resolution observation and analysis of graphene constrictions and ribbons with sub-nanometer width. Graphene membranes are studied by imaging side spherical aberration-corrected transmission electron microscopy at 80 kV. Holes are formed in the honeycomb-like structure due to radiation damage. As the holes grow and two holes approach each other, the hexagonal structure that lies between them narrows down. Transitions and deviations from the hexagonal structure in this graphene ribbon occur as its width shrinks below one nanometer. Some reconstructions, involving more pentagons and heptagons than hexagons, turn out to be surprisingly stable. Finally, single carbon atom chain bridges between graphene contacts are observed. The dynamics are observed in real time at atomic resolution with enough sensitivity to detect every carbon atom that remains stable for a sufficient amount of time. The carbon chains appear reproducibly and in various configurations from graphene bridges, between adsorbates, or at open edges and seem to represent one of the most stable configurations that a few-atomic carbon system accomodates in the presence of continuous energy input from the electron beam.Comment: 12 pages, 4 figure

Towards reliable diagnostics of prostate cancer via breath

Early detection of cancer is a key ingredient for saving many lives. Unfortunately, cancers of the urogenital system are difficult to detect at early stage. The existing noninvasive diagnostics of prostate cancer (PCa) suffer from low accuracy (< 70%) even at advanced stages. In an attempt to improve the accuracy, a small breath study of 63 volunteers representing three groups: (1) of 19 healthy, (2) 28 with PCa, (3) with 8 kidney cancer (KC) and 8 bladder cancer (BC) was performed. Ultrabroadband mid-infrared Fourier absorption spectroscopy revealed eight spectral ranges (SRs) that differentiate the groups. The resulting accuracies of supervised analyses exceeded 95% for four SRs in distinguishing (1) vs (2), three for (1) vs (3) and four SRs for (1) vs (2) + (3). The SRs were then attributed to volatile metabolites. Their origin and involvement in urogenital carcinogenesis are discussed

Time-resolved x-ray spectroscopy of optical-field-ionized plasmas

The time-dependent soft X-ray emission of helium and nitrogen plasmas generated by optical-field ionization is reported. The experiments were carried out by focusing pulses of the high-power Ti:sapphire laser of the Lund Institute of Technology (lambda = 796 nm, pulse duration 150 fs, pulse energy 150 mJ) to a 50-mu m diameter spot close to a nozzle, using He and N-2 as target gases. The emission on He+, N4+, and N3+ resonance lines was recorded by means of a flat-field grating spectrometer coupled to an X-ray streak camera. A pronounced difference in the temporal shape of the emission of the Lyman-alpha line of hydrogen-like helium and of the 2p-3d resonance lines of lithium-like and beryllium-like nitrogen was observed. The helium line exhibited an initial spike followed by a slow revival of the emission, whereas the nitrogen lines showed a slow decay after a fast initial rise. These observations are explained with the help of simulations

High resolution two-dimensional near field images of neon-like soft x- ray lasers

We discuss high resolution two-dimensional near-field images of the neon-like nickel and germanium X-ray laser. The Asterix iodine laser, using a prepulse 5.23 ns before the main pulse, was used to irradiate slab targets. Our imaging diagnostic consisted of a concave multilayer mirror that imaged the X-ray laser line (with a magnification of ten) onto a backside illuminated X-ray CCD detector. A great deal of structure was observed in the near field images, particularly in the J=0-1 emission. We observed a large difference in the spatial dependence of the J=0-1 and J=2-1 lines of germanium, with the J=2-1 emission peaking farther away from the original target surface. The prepulse level was varied and observed to have a significant effect on the spatial dependence of the germanium and nickel laser lines. A larger prepulse moved the peak emission farther away from the target surface. These measurements are generally consistent with hydrodynamic simulations coupled with atomic kinetics