Combining laser interferometry and plasma spectroscopy for spatially resolved high-sensitivity plasma density measurements in discharge capillaries

Precise characterization and tailoring of the spatial and temporal evolution of plasma density within plasma sources are critical for realizing high-quality accelerated beams in plasma wakefield accelerators. The simultaneous use of two independent diagnostics allowed the temporally and spatially resolved detection of plasma density with unprecedented sensitivity and enabled the characterization of the plasma temperature in discharge capillaries for times later than 0.5 µs after the initiation of the discharge, at which point the plasma is at local thermodynamic equilibrium. A common-path two-color laser interferometer for obtaining the average plasma density with a sensitivity of 2 × 10¹⁵ cm^-2 was developed together with a plasma emission spectrometer for analyzing spectral line broadening profiles with a resolution of 5 × 10¹⁵ cm^-3. Both diagnostics show good agreement when applying the spectral line broadening analysis methodology of Gigosos and Cardeñoso in the temperature range of 0.5 eV-5.0 eV. For plasma with densities of 0.5-2.5 × 10¹⁷ cm^-3, temperatures of 1 eV-7 eV were indirectly measured by combining the diagnostic information. Measured longitudinally resolved plasma density profiles exhibit a clear temporal evolution from an initial flat-top to a Gaussian-like shape in the first microseconds as material is ejected out from the capillary. These measurements pave the way for highly detailed parameter tuning in plasma sources for particle accelerators and beam optics.

FLASHForward: plasma wakefield accelerator science for high-average-power applications

The FLASHForward experimental facility is a high-performance test-bed for precision plasma wakefield research, aiming to accelerate high-quality electron beams to GeV-levels in a few centimetres of ionized gas. The plasma is created by ionizing gas in a gas cell either by a high-voltage discharge or a high-intensity laser pulse. The electrons to be accelerated will either be injected internally from the plasma background or externally from the FLASH superconducting RF front end. In both cases, the wakefield will be driven by electron beams provided by the FLASH gun and linac modules operating with a 10 Hz macro-pulse structure, generating 1.25 GeV, 1 nC electron bunches at up to 3 MHz micro-pulse repetition rates. At full capacity, this FLASH bunch-train structure corresponds to 30 kW of average power, orders of magnitude higher than drivers available to other state-of-the-art LWFA and PWFA experiments. This high-power functionality means FLASHForward is the only plasma wakefield facility in the world with the immediate capability to develop, explore and benchmark high-average-power plasma wakefield research essential for next-generation facilities. The operational parameters and technical highlights of the experiment are discussed, as well as the scientific goals and high-average-power outlook. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Tunable Plasma-Based Energy Dechirper

A tunable plasma-based energy dechirper has been developed at FLASHForward to remove the correlated energy spread of a 681 MeV electron bunch. Through the interaction of the bunch with wakefields excited in plasma the projected energy spread was reduced from a FWHM of 1.31% to 0.33% without reducing the stability of the incoming beam. The experimental results for variable plasma density are in good agreement with analytic predictions and three-dimensional simulations. The proof-of-principle dechirping strength of 1.8  GeV/mm/m significantly exceeds those demonstrated for competing state-of-the-art techniques and may be key to future plasma wakefield-based free-electron lasers and high energy physics facilities, where large intrinsic chirps need to be removed.

A Terminological and Ontological Analysis of the NCI Thesaurus

Objective: The National Cancer Institute Thesaurus is described by its authors as “a biomedical vocabulary that provides consistent, unambiguous codes and definitions for concepts used in cancer research” and which “exhibits ontology-like properties in its construction and use”. We performed a qualitative analysis of the Thesaurus in order to assess its conformity with principles of good practice in terminology and ontology design.

Materials and Methods: We used both the on-line browsable version of the Thesaurus and its OWL-representation (version 04.08b, released on August 2, 2004), measuring each in light of the requirements put forward in relevant ISO terminology standards and in light of ontological principles advanced in the recent literature.

Results: We found many mistakes and inconsistencies with respect to the term-formation principles used, the underlying knowledge representation system, and missing or inappropriately assigned verbal and formal definitions.

Conclusion: Version 04.08b of the NCI Thesaurus suffers from the same broad range of problems that have been observed in other biomedical terminologies. For its further development, we recommend the use of a more principled approach that allows the Thesaurus to be tested not just for internal consistency but also for its degree of correspondence to that part of reality which it is designed to represent.

A revisionist history of adult marrow stem cell biology or 'they forgot about the discard'

The adult marrow hematopoietic stem cell biology has largely been based on studies of highly purified stem cells. This is unfortunate because during the stem cell purification the great bulk of stem cells are discarded. These cells are actively proliferating. The final purified stem cell is dormant and not representative of the whole stem cell compartment. Thus, a large number of studies on the cellular characteristics, regulators and molecular details of stem cells have been carried on out of non-represented cells. Niche studies have largely pursued using these purified stem cells and these are largely un-interpretable. Other considerations include the distinction between baseline and transplant stem cells and the modulation of stem cell phenotype by extracellular vesicles, to cite a non-inclusive list. Work needs to proceed on characterizing the true stem cell population.

Mesenchymal stromal cell-derived extracellular vesicles rescue radiation damage to murine marrow hematopoietic cells

Mesenchymal stromal cells (MSCs) have been shown to reverse radiation damage to marrow stem cells. We have evaluated the capacity of MSC-derived extracellular vesicles (MSC-EVs) to mitigate radiation injury to marrow stem cells at 4 h to 7 days after irradiation. Significant restoration of marrow stem cell engraftment at 4, 24 and 168 h post irradiation by exposure to MSC-EVs was observed at 3 weeks to 9 months after transplant and further confirmed by secondary engraftment. Intravenous injection of MSC-EVs to 500cGy exposed mice led to partial recovery of peripheral blood counts and restoration of the engraftment of marrow. The murine hematopoietic cell line, FDC-P1 exposed to 500cGy, showed reversal of growth inhibition, DNA damage and apoptosis on exposure to murine or human MSC-EVs. Both murine and human MSC-EVs reverse radiation damage to murine marrow cells and stimulate normal murine marrow stem cell/progenitors to proliferate. A preparation with both exosomes and microvesicles was found to be superior to either microvesicles or exosomes alone. Biologic activity was seen in freshly isolated vesicles and in vesicles stored for up to 6 months in 10% dimethyl sulfoxide at -80 °C. These studies indicate that MSC-EVs can reverse radiation damage to bone marrow stem cells.

Relation between drug-induced central nervous system effects and plasma levels of diazepam in man

Pharmacodynamic effects and plasma levels of diazepam were studied in healthy male volunteers at different dose levels. Responses to diazepam were quantified, using instruments which measured body sway (statometry) and psychomotor performance (stressalyser tests). High dose-related correlations were obtained between drug-induced changes in test parameters and drug plasma levels, both with regard to stimulant and depressive effects. Techniques were devised for evaluating and comparing the efficacy and usefulness of different types of tests, taking into account critical thresholds, slopes and error estimates, correcting for changes in predrug levels and control (nondrug) trials.

The sociodemographic patterning of opposition to raising taxes on tobacco and restricting tobacco advertisements in Argentina

BACKGROUND

Argentina has enacted important tobacco control initiatives in recent years. Yet little is known about the social patterning of attitudes toward tobacco control. Research is needed to explore what predicts opposition to tobacco control initiatives such as higher taxes on tobacco and the prohibition of tobacco advertising.

STUDY DESIGN

Secondary analysis of Argentina's Global Adult Tobacco Survey (N = 6645).

METHODS

Binary logistic regression analysis examining opposition to raising tobacco taxes and banning tobacco publicity. Models were stratified by smoking status.

RESULTS

Respondents generally indicated very little opposition to either tobacco control measure, with only 15.6% of respondents opposed to increasing taxes on tobacco products and 9.6% opposed to banning tobacco advertisements. Smoking status is the most important predictor of opposition to increasing taxes (OR = 7.85, 95% CI = 6.60-9.34) and banning advertisements (OR = 1.72, 95% CI = 1.39-2.11). Opposition to these measures is most likely among young respondents (aged 15-24) and least likely among older age groups (55-64 and 65 or over), compared to the 25-34 age group. Stratified models suggest that the effect of age may be different for smokers and non-smokers. Low income is a significant predictor of opposition, but only in stratified models for smokers.

CONCLUSION

There is general support for stronger tobacco control measures in Argentina. Opposition to raising taxes on tobacco products and banning tobacco advertisement appears to be concentrated among young smokers with low and medium levels of household income.

Overexpression of ERG in cord blood progenitors promotes expansion and recapitulates molecular signatures of high ERG leukemias

High expression of the ETS family transcription factor ERG is associated with poor clinical outcome in acute myeloid leukemia (AML) and acute T-cell lymphoblastic leukemia (T-ALL). In murine models, high ERG expression induces both T-ALL and AML. However, no study to date has defined the effect of high ERG expression on primary human hematopoietic cells. In the present study, human CD34+ cells were transduced with retroviral vectors to elevate ERG gene expression to levels detected in high ERG AML. RNA sequencing was performed on purified populations of transduced cells to define the effects of high ERG on gene expression in human CD34+ cells. Integration of the genome-wide expression data with other data sets revealed that high ERG drives an expression signature that shares features of normal hematopoietic stem cells, high ERG AMLs, early T-cell precursor-ALLs and leukemic stem cell signatures associated with poor clinical outcome. Functional assays linked this gene expression profile to enhanced progenitor cell expansion. These results support a model whereby a stem cell gene expression network driven by high ERG in human cells enhances the expansion of the progenitor pool, providing opportunity for the acquisition and propagation of mutations and the development of leukemia.

Sex-stratified and age-adjusted social gradients in tobacco in Argentina and Uruguay: evidence from the Global Adult Tobacco Survey (GATS)

OBJECTIVE

To examine social gradients in tobacco use in Argentina and Uruguay, using newly available directly comparable data sets.

METHODS

Secondary analysis of Global Adult Tobacco Survey data from Argentina (N=6645) and Uruguay (N=5581). Social gradients in current tobacco use, exposure to secondhand smoke, and cessation attempt were examined with sex-stratified and age-adjusted logistic regression.

RESULTS

Among men, there is evidence of higher odds of being a current smoker among respondents with lower levels of education, but the association is only statistically significant for respondents with less than primary education in Uruguay (OR=2.15, 95% CI 1.22 to 3.77). Similarly, women with lower levels of education have higher odds of being a current smoker in Uruguay. The association between education and exposure to secondhand smoke is broadly similar for both sexes in both countries, with generally higher odds among groups with low education, though the relationship is only statistically significant among men in Uruguay (OR=1.77, 95% CI 1.08 to 2.92). In both countries, respondents with lower levels of education in general have higher odds of having attempted to quit smoking in the past year, although these associations did not attain statistical significance.

CONCLUSIONS

Social gradients in tobacco use, exposure to secondhand smoke and cessation attempts are broadly similar in both countries. Efforts to evaluate the long-term effects of tobacco control efforts in these countries should monitor how policies affect national averages, and the social gradients that are embedded in aggregate data.

Sudden cardiac arrest risk in young athletes

Underlying cardiac abnormalities are the main cause of unexpected death in athletes on field. These abnormalities have been associated with a previous history of syncope, a family history of sudden cardiac arrest (SCA), cardiac murmur, a history of over-exhaustion post exercise and ventricular  tachyarrhythmia during physical activity. The timely diagnosis of susceptible athletes may assist with an appropriate management plan for these individuals, and allow for the prevention of premature death in sport. A young football player was screened for SCA risk using the fundamental components of the pre-participation examination (PPE) – essentially, a medical history, a resting and stress electrocardiogram, and an echocardiogram to support clinical findings. The case is submitted with consideration of the applicable literature to accentuate the importance of using PPE to prevent SCA in young athletes.