Gating a Single Cell:A Label-Free and Real-Time Measurement Method for Cellular Progression

There is an ever-growing need for more advanced methods to study the response of cancer cells to new therapies. To determine cancer cells’ response from a cell-mortality perspective to various cancer therapies, we report a label-free and real time method to monitor the in situ response of individual HeLa cells using a single cell gated transistor (SCGT). As a cell undergoes apoptotic cell death, it experiences changes in morphology and ion concentrations. This change is well in line with the threshold voltage of the SCGT, which has been verified by correlating the data with the cell morphologies by scanning electron microscopy and the ion-concentration analysis by inductively-coupled plasma mass spectrometry (ICPMS). This SCGT could replace patch clamps to study single cell activity via direct measurement in real time. Importantly, this SCGT can be used to study the electrical response of a single cell to stimuli that leaves the membrane intact

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

The first author h-index (hfa-index): levelling the field for small and large institute medical and science scholars

Recent editorials and debates in the literature have highlighted the h-index measurement scale for researchers and how it can be used as a measure of their contributions to the medical and scientific community [1–5]. Indeed, in many University Institutions, the h-index (or h-factor) is being employed for assessment of regrading applications and for individual academics impact. So like it or not, it is here to stay and play. Whilst the debate will continue, it is definite that there are factors which can weight the h-index value to either advantage or disadvantage the researcher. Baldock [6] quite elegantly pointed out how subtle ways of citing papers can occur to benefit one’s h-index. This is inevitable. However, one area where substantial improvements could be made to the h-index may lie in the area of enhancing the h-index score by weighting first author papers or a hfa-index. This may not be practical if a large proportion of journals used alphabetical listings for authors. However this practice is not common and a well established researcher would normally publish in multiple journals reducing this overall effect. Upon investigation, according to the ISI Journal Citation Reports 2009, of the top 20 journals ranked in the subsection of ‘‘Radiology, Nuclear Medicine and Medical Imaging’’, no journals used alphabetical name order convention

Trans-oceanic transport of \u3c sup\u3e 137 \u3c/sup\u3e Cs from the Fukushima nuclear accident and impact of hypothetical Fukushima-like events of future nuclear plants in Southern China

© 2014 Elsevier B.V. A Lagrangian model was adopted to assess the potential impact of 137Cs released from hypothetical Fukushima-like accidents occurring on three potential nuclear power plant sites in Southern China in the near future (planned within 10years) in four different seasons. The maximum surface (0-500m) 137Cs air concentrations would be reached 10Bqm-3 near the source, comparable to the Fukushima case. In January, Southeast Asian countries would be mostly affected by the radioactive plume due to the effects of winter monsoon. In April, the impact would be mainly on Southern and Northern China. Debris of radioactive plume (~1mBqm-3) would carry out long-range transport to North America. The area of influence would be the smallest in July due to the frequent and intense wet removal events by trough of low pressure and tropical cyclone. The maximum worst-case areas of influence were 2382000, 2327000, 517000 and 1395000km2 in January, April, July and October, respectively.Prior to the above calculations, the model was employed to simulate the trans-oceanic transport of 137Cs from the Fukushima nuclear accident. Observed and modeled 137Cs concentrations were comparable. Sensitivity runs were performed to optimize the wet scavenging parameterization. The adoption of higher-resolution (1°×1°) meteorological fields improved the prediction. The computed large-scale plume transport pattern over the Pacific Ocean was compared with that reported in the literature

Radiochromic film for verification of superficial x-ray backscatter factors

Accurate calculation and knowledge of backscatter factors (BSF) in superficial x-ray radiotherapy is required to perform accurate absorbed dose determination. These measurements have been performed historically with small thin parallel plate ionisation chambers and Thermoluminescent Dosimeters (TLD′s). This note investigates the use of a low energy dependence radiochromic thin film (GAFCHROMICTM EBT) for measurement and verification of backscatter factors. A single layer film and an extrapolation method with multiple films have been investigated. 50kVp to 150kVp beams were analysed and results for BSF were measured and compared to IPEMB (Institution of Physics and Engineering in Medicine and Biology UK) derived results. Agreement within 2% (1 SD) was found using both the single layer and extrapolation techniques with IPEMB derived results at 30cm SSD and equivalent photon energies. A 150kVp beam was found to have BSF of 1.12±0.02 (2cm circle) , 1.24±0.01 (5cm circle), 1.36±0.02 (10cm circle) respectively compared to 1.11, 1.23 and 1.36 for IPEMB derived results. In summary a single layer film provided an accurate measurement and verification of BSF and was found to be within 2% of derived IPEMB results in all cases. The extrapolation method in general provided a slightly closer match to IPEMB results (\u3c1%) but with no extra discernable accuracy than the single layer film most likely due to the already small thickness (0.3mm) of one film piece. GAFCHROMICTM EBT, Radiochromic film provides a very simple and easy method for measurement and verification of BSF for x-ray energies commonly used for superficial x-ray therapy

Megavoltage x-ray skin dose variation with an angle using grid carbon fibre couch tops

It is well known that a skin dose from high-energy x-ray radiation varies with the angle of beam incidence or the presence of a radiotherapy linear accelerator couch top material. This note investigates changes produced to the skin dose from a Varian carbon fibre grid couch top at differing angles of incidence for 6 MV x-rays as is often the case clinically. Results have shown that the skin dose can easily be measured using an EBT Gafchromic film whereby the delivered skin dose can be quantified to a high level of spatial resolution, not easily achieved with other skin dose detectors. Results have shown a significant increase in the skin dose specifically at the point of a cross-sectional carbon fibre grid. Values in % of the skin dose increased from approximately 27% (an open area within a 10 cm × 10 cm field) up to 55% (same field size) at the centre of the carbon fibre mesh strip (0° incidence). This is compared to 19% of the skin dose for an open field of a 10 cm × 10 cm beam without the couch material present. At larger angles similar effects occur with values changing from 52% to 75% (60°, 10 cm × 10 cm) in the open area and under the grid, respectively. This produces a wave effect for the skin dose. The average skin dose magnitude increases with the angle of incidence of the beam, ranging from 37.5% to 66% from 0° to 60° (10 × 10 cm), respectively. The symmetric wave nature of the skin dose profile skews to deliver an increased dose on the posterior side of the carbon fibre grid as the angle of incidence increases. Simulated fractional dose delivery on a phantom has shown that over 30 fractions the wave nature of the delivered skin dose is minimized due to the random nature of most patient positioning on the treatment couch. However, some variations are still present as the ratio of the open to grid area is approximately 4:1 and the dose spread is not necessarily completely averaged during a typical fractionated radiotherapy treatment. As such, if the treatment type results in a more rigorously positioned patient on the treatment couch, the wave nature of skin dose delivery may need to be taken into account

Measurement of dose reductions for superficial x-rays backscattered from bone interfaces.

Accurate measurement and knowledge of dose delivered during superficial x-ray radiotherapy is required for patient dose assessment. Some tumours treated near the surface (within the first few centimetres) can have large posterior bone structures. This can cause perturbations to dose delivered due to changed backscatter contributions from the bony structure as compared to full water or tissue scattering conditions. Measured results have shown that up to 7.5% of Dmax reductions in dose can occur near the water/bone interface for 100 kVp, using 10 cm diameter field sizes when a 1 cm thick slab of bone is located at 2 cm depth. At smaller field sizes such as 2 cm diameter these values reduce to 2% for the same energy. Larger variations (up to 12.5% of maximum) have been seen at the phantom surface when the bone layer is directly behind the point of interest (within 0.5 mm) and smaller effects (up to 5% of maximum) at depths down to 5 cm. Interesting to note is the fact that for larger field sizes, an increase in percentage dose is found at the water/bone interface due to the production of low energy backscattered electrons similar to the effect found in lead. However, they are much smaller in magnitude and thus would not cause any significant dosimetric effects. In the case where large bony structures lie relatively close to the surface and the tissue above this region is being treated, a dosimeter such as radiochromic film can be used to estimate the dose reduction that may occur due to the changed backscatter conditions

Measuring energy response for RTQA radiochromic film to improve quality assurance procedures

RTQA Gafchromic, radiochromic film is assessed for its radiation energy dependence in photon beams ranging from superficial to megavoltage energies. RTQA radiochromic film has uses in radiation quality assurance procedures due to its auto development and visualisation properties. These properties allow for immediate comparison of x-ray alignment and coincidence not available with radiographic films. Results show that the RTQA film produces an energy dependant darkening to x-rays which results in x-ray energies of 69 keV photon equivalent (150 kVp) to produce 2.14 times the optical density to dose ratio of a 6MV x-ray beam. The following dose ratio\u27s (normalized to 1 at 150 kVp) provide the same net optical density change for RTQA film. 1.47-50 kVp : 1.21-75 kVp : 1.09-100 kVp : 1.01-125 kVp: 1.00-150 kVp : 1.03-200 kVp : 1.07-250 kVp : 2.14-6 MVp : 2.14 10 MVp. Although the film is not designed to be used as a quantitative measure of radiation it is still useful to know its energy response at differing x-ray energies to expose the film to the appropriate dose to provide optimal darkening characteristics for a given QA test at the appropriate energy. Our results have shown that a 0.3 optical density change with RTQA film provides a colour change level useable for accurate alignment procedure