Experimental Electrohydrodynamic Nanospray Production Using Drawn Glass Capillaries

This article describes a simple and low-cost method of fabricating glass capillary nanospray emitter sources, and, if required, inserting a charging electrode. Initial experimental work employing such a source is described, whose results suggest that whilst the positioning of the charging electrode relative to the orifice influences the charging current and spray considerably, this position may not correspond with that previously reported as being ideal for electrospray systems one or two orders of magnitude greater.     

The direct measurement of embryogenic volume and nucleo-cytoplasmic ratio during mouse pre-implantation development

Stringent selection mechanisms, in both internal and external fertilisation systems, reject all but a significant minority of the spermatozoa released at ejaculation. Sperm competition theory provides circumstantial evidence that the selection process involves mechanisms by which the quality of the fertilising spermatozoon is controlled, thereby ensuring that females and their offspring receive high quality genetic material. In this review we examine some of these selection processes to see whether they could be exploited for the improvement of laboratory tests of sperm quality. Such tests are not only required for clinical and agricultural purposes, but are increasingly needed in fields such as reproductive and environmental toxicology where the species requirement is much broader. Despite many years of research, sperm quality assessment methods continue to provide imprecise data about fertility; here we suggest that this may be a consequence of using tests that focus on the spermatozoa that would normally be unable to fertilise under natural conditions. To achieve fertilisation a spermatozoon must be capable of responding appropriately to external signalling stimuli; those involving protein kinase-regulated flagellar function seem especially influential in governing effects ranging from non-Mendelian inheritance in mammals to sperm chemotaxis in sea urchins. Examination of the elicited responses reveals considerable heterogeneity in all species. Here we propose that this level of heterogeneity is meaningful both in terms of understanding how spermatozoa from some individuals possess fertility advantages over spermatozoa from their rivals in sperm competition, and in that the heterogeneity should be exploitable in the development of more accurate laboratory tests.     

Evidence that activation of Src family kinase is not required for fertilization-associated [Ca2+]i oscillations in mouse eggs

Recent evidence in marine invertebrate, frog, and zebrafish eggs suggests the involvement of a Src family kinase (SFK) in fertilization-induced Ca2+ release. In the present study, we have investigated whether activation of an SFK is required for initiation of intracellular Ca2+ ([Ca2+]i) oscillations in mouse fertilization. We detected a Hck-like protein and tyrosine-phosphorylated proteins in soluble and insoluble sperm fractions, respectively. However, the presence of these proteins did not correspond to the active fractions of porcine sperm extracts (pSE). Moreover, [Ca2+]i oscillations induced by pSE in mouse eggs were unaltered by pre-incubation of pSE with specific SFK inhibitors such as 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]-pyrimidine (PP2) or lavendustin A, despite the fact that the inhibitors were shown to be active both in vivo and in vitro. Another SFK inhibitor, peptide A, blocked oscillations when incubated with pSE prior to injection into eggs, but this inhibition required more than ten times the concentration reportedly required to inhibit SFK activity. In addition, pre-injection or pre-incubation of eggs with these inhibitors did not affect the ability of pSE to trigger [Ca2+]i oscillations in mouse eggs. Microinjection of a recombinant c-Src protein or mRNAs encoding constitutively active Src proteins did not induce [Ca2+]i release. Finally, when sperm and eggs, both of which were pre-treated with PP2, were fertilized, [Ca2+]i oscillations occurred normally. We can therefore conclude that activation of an SFK is neither necessary nor sufficient for triggering fertilization-induced [Ca2+]i oscillations.     

Propagation of terahertz pulses in random media

We describe measurements of single-cycle terahertz pulse propagation in a random medium. The unique capabilities of terahertz time-domain spectroscopy permit the characterization of a multiply scattered field with unprecedented spatial and temporal resolution. With these results, we can develop a framework for understanding the statistics of broadband laser speckle. Also, the ability to extract information on the phase of the field opens up new possibilities for characterizing multiply scattered waves. We illustrate this with a simple example, which involves computing a time-windowed temporal correlation between fields measured at different spatial locations. This enables the identification of individual scattering events, and could lead to a new method for imaging in random media.     

Electrochemical detection of single-nucleotide mismatches: application of M-DNA

The detection of a single-nucleotide mismatch in unlabeled duplex DNA by electrochemical methods is presented. Impedance spectroscopy is used to characterize a perfect duplex monolayer and three DNA monolayers differing in the position of the mismatch. The monolayers were studied as B-DNA (normal duplex DNA) and after conversion to M-DNA (a metalated duplex). Modeling of the impedance data to an equivalent circuit provides parameters that are useful in discriminating the four monolayer configurations. The resistance to charge transfer, R(CT), was lower for all duplexes after conversion to M-DNA. Contrary to expectations, R(CT) was also found to decrease for duplexes containing a mismatch. However, R(CT) was found to be diagnostic for mismatch detection. In particular, the difference in R(CT) between B- and M-DNA (deltaR(CT)) decreased from 190(22) omega.cm(2) for a perfectly matched duplex to 95(20), 30(20), and 85(20) omega.cm(2) for a mismatch at the top (distal), middle, and bottom (proximal) positions of the monolayer with respect to the gold surface. Further, a method to form loosely packed single-stranded (ss)-DNA monolayers by duplex dehybridization that is able to rehybridize to target strands is presented. Rehybridization efficiencies were in the range of 40-70%. Under incomplete hybridization conditions, the R(CT) was the same for matched and mismatched duplexes under B-DNA conditions. However, deltaR(CT) between B- and M-DNA, under incomplete hybridization, still provided a distinction. The deltaR(CT) for a perfect duplex was 76(12) omega.cm(2), whereas a mismatch in the middle of the sequence yielded a deltaR(CT) value of 30(15) omega.cm(2). The detection limit was measured and the impedance methodology reliably detected single DNA base pair mismatches at concentrations as low as 100 pM.     

Sample classification based on Bayesian spectral decomposition of metabonomic NMR data sets

1H NMR spectra of biofluids provides a wealth of biochemical information on the metabolic status of an organism. Through the application of pattern recognition and classification algorithms, the data have been shown to provide information on disease diagnosis and the beneficial and adverse effects of potential therapeutics. Here, a novel approach is described for identifying subsets of spectral patterns in databases of NMR spectra, and it is shown that the intensities of these spectral patterns can be related to the onset and recovery from a toxic lesion in both a time-related and dose-related fashion. These patterns form a new type of combination biomarker for the biological effect under study. The approach is illustrated with a study of liver toxicity in rats using NMR spectra of urine following administration of a model hepatotoxin hydrazine.     

A Review of the U.S. Department of Energy's Inertial Fusion Energy Program

This is the final report of a panel set up by the U.S. Department of Energy (DOE) Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter from Dr. Ray Orbach (Appendix A). In that letter, Dr. Orbach asked FESAC for an assessment of the present status of inertial fusion energy (IFE) research carried out in contributing programs. These programs include the heavy ion (HI) beam, the high average power laser (HAPL), and Z-Pinch drivers and associated technologies, including fast ignition (FI). This report, presented to FESAC on March 29, 2004, and subsequently approved by them (Appendix B), presents FESAC's response to that charge.     

Synthetic aperture interferometry: in-process measurement of aspheric optics

A scanning probe consisting of a source and receive fiber pair is used to measure the phase difference between wave fronts scattered from the front and rear surfaces of an aspheric optic. This system can be thought of as a classical interferometer with an aperture synthesized from the data collected along the path of the probe. If the form of either surface is known, the other can be deduced. In contrast with classical interferometers, the method does not need test or null plates and has the potential to be integrated into the manufacturing process.     

The benefits of improved car secondary safety

The term 'secondary safety' refers to the protection that a vehicle provides its occupants when involved in an accident. This paper studies information from the British database of road accident reports between 1980 and 1998, to estimate the reduction in the number of occupant casualties over these years which may be attributed to improvements to secondary safety in cars.The paper shows that the proportion of driver casualties who are killed or seriously injured (KSI) is lower for modern cars than for older cars. The reduction of this proportion is used to assess the improvement in secondary safety. Statistical models are developed to represent the proportion with 'year of first registration' as one of the independent variables, although only an incomplete assessment of the benefits of improved secondary safety can be made with the available data. The assessment compares the number of casualties that would have been expected if secondary safety had remained at the level found in cars first registered in 1980 with the actual casualty numbers. It is estimated that improved secondary safety reduced the number of drivers KSI by at least 19.7% in 1998, in comparison with what might have occurred if all cars had had that lower level of secondary safety. This figure relates to all cars on the road in 1998, and rises to 33%, when confined to the most modern cars (those which were first registered in 1998).