In Situ Measurement of Electron Energy Evolution in a Laser-Plasma Accelerator.

We report on a novel, noninvasive method applying Thomson scattering to measure the evolution of the electron beam energy inside a laser-plasma accelerator with high spatial resolution. The determination of the local electron energy enabled the in-situ detection of the acting acceleration fields without altering the final beam state. In this Letter we demonstrate that the accelerating fields evolve from (265±119) GV/m to (9±4) GV/m in a plasma density ramp. The presented data show excellent agreement with particle-in-cell simulations. This method provides new possibilities for detecting the dynamics of plasma-based accelerators and their optimization.

Longer storage of red blood cells is associated with increased in vitro erythrophagocytosis.

BACKGROUND AND OBJECTIVES: Refrigerated storage of red blood cells (RBCs) induces numerous changes that may target the cells for erythrophagocytosis following transfusion. The influence of storage upon the phagocytosis of unseparated and fractionated young and old stored RBCs was investigated using two in vitro quantitative phagocytosis assays. MATERIALS AND METHODS: Leucocyte-depleted RBC units were sampled at day 1 or 42 of storage. Young and old RBCs were fractionated at day 1 by density centrifugation and stored in paediatric packs for up to 42 days. RBCs were labelled with the fluorescent dye PKH26 and incubated with the human monocytic cell line THP-1. Erythrophagocytosis was quantified by flow cytometry and plate fluorometric assays. RESULTS: A higher proportion of THP-1 cells phagocytosed RBCs stored for 42 days compared with 1 day (41% and 24% respectively; P<0·0001). This was associated with an increased mean number of RBCs phagocytosed per THP-1 cell (5·2±0·6 and 3·3±0·2 respectively; P<0·002). Erythrophagocytosis of fractionated young and old RBCs increased with longer storage duration up to 28 days (P<0·05). However, no significant differences were observed between erythrophagocytosis of young and old RBCs. CONCLUSION: The susceptibility of stored RBCs to erythrophagocytosis significantly increased with longer storage time of the RBC units. Storage duration of RBCs had a greater influence on in vitro erythrophagocytosis than the chronological age of the RBCs at donation.

Analysis of a neutron-induced conversion electron spectrum of gadolinium.

A 100-nm-thick gadolinium layer deposited on a pixelated silicon sensor was activated in a neutron field to measure the internal conversion electron (ICE) spectrum generated by neutron capture products of 155Gd and 157Gd. The experiment was performed at the ISIS neutron and muon facility, using a bespoke version of the HEXITEC spectroscopic imaging camera. Signals originating from internal conversion electrons, Auger electrons, x rays and gamma rays up to 150 keV were identified. The ICE spectrum has an energy resolution of 1.8-1.9 keV at 72 keV and shows peaks from the K, L, M, N+ ICEs of the 79.51 keV and 88.967 keV 2+-0+ gamma transitions from the first excited states in 158Gd and 156Gd, respectively, as well as the K ICEs of the 4+-2+ transitions at 181.931 keV and 199.213 keV from the respective second excited states. Spectrum analysis was performed using a convolution of a Gaussian with exponential functions at the low and high energy side as the peak shaping function. Relative ICE intensities were derived from the fitted peak areas and compared with internal conversion coefficient (ICC) values calculated from the BrIcc database. Relative to the dominant L shell contribution, the K ICE intensity conforms to BrIcc and the M, N, O+ ICE intensities are somewhat higher than expected.

Single-shot structural analysis by high-energy X-ray diffraction using an ultrashort all-optical source.

High-energy X-rays (HEX-rays) with photon energies on order of 100 keV have attractive characteristics, such as comparably low absorption, high spatial resolution and the ability to access inner-shell states of heavy atoms. These properties are advantageous for many applications ranging from studies of bulk materials to the investigation of materials in extreme conditions. Ultrafast X-ray diffraction allows the direct imaging of atomic dynamics simultaneously on its natural time and length scale. However, using HEX-rays for ultrafast studies has been limited due to the lack of sources that can generate pulses of sufficiently short (femtosecond) duration in this wavelength range. Here we show single-crystal diffraction using ultrashort ~90 keV HEX-ray pulses generated by an all-optical source based on inverse Compton scattering. We also demonstrate a method for measuring the crystal lattice spacing in a single shot that contains only ~105 photons in a spectral bandwidth of ~50% full width at half maximum (FWHM). Our approach allows us to obtain structural information from the full X-ray spectrum. As target we use a cylindrically bent Ge crystal in Laue transmission geometry. This experiment constitutes a first step towards measurements of ultrafast atomic dynamics using femtosecond HEX-ray pulses.

Scatter free imaging for the improvement of breast cancer detection in mammography.

In mammography, the reduction of scattered x-rays is vital due to the low contrast or small dimension of the details that are searched for. The typical method of doing so in current conventional mammography is the anti-scatter grid. The disadvantage of this method is the absorption of a proportion of the primary beam and therefore an increase in dose is required to compensate for the loss of counts. An alternative method is proposed, using quasi-monochromatic beams and a pixellated spectroscopic detector. As Compton-scattered x-rays lose energy in the scattering process, they are detected at a lower energy in the spectrum. Therefore the spectrum can be windowed around the monochromatic energy peak, removing the scattered x-rays from the image. The work presented here shows contrast improvement of up to 50% and contrast to noise ratio improvements of around 20% for scatter free imaging in comparison to full spectrum imaging. Contrast improvements of around 45% were found when comparing scatter free images to conventional polychromatic imaging for both the low contrast test object and the Rachel anthropomorphic breast phantom.

Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging.

The recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense laser probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.

1H-NMR visible neutral lipids in activated T lymphocytes: relationship to phosphatidylcholine cycling.

Two-dimensional 1H-NMR spectroscopy was used to compare changes in the concentration of isotropically-tumbling neutral lipid during the activation of splenic and thymic T lymphocytes. The concentration of mobile neutral lipid (MNL) was similar in splenic and thymic T cells after 72 h of activation with phorbol myristate acetate and ionomycin. However, after 120 h of activation, MNL concentrations in splenic T cells were more than 3-fold higher than in thymic T cells. An increase in choline (Cho), phosphocholine (PCho) and glycerophosphocholine (GPC) was also observed in both thymic and splenic T cells after 24 h of activation. However, after 72 h of stimulation, Cho and PCho levels had decreased and continued to decline at 96-120 h, while GPC continued to be maintained at elevated levels. The simultaneous increase in MNL and GPC and the decline in Cho and PCho leads us to propose that the synthesis of NMR-visible MNL in activated lymphocytes is linked to the phosphatidylcholine cycle.

Mapping of multi-elements during melting and solidification using synchrotron X-rays and pixel-based spectroscopy.

A new synchrotron-based technique for elemental imaging that combines radiography and fluorescence spectroscopy has been developed and applied to study the spatial distribution of Ag, Zr and Mo in an Al alloy during heating and melting to 700, and then re-soldification. For the first time, multi-element distributions have been mapped independently and simultaneously, showing the dissolution of Ag- and Zr-rich particles during melting and the inter-dendritic segregation of Ag during re-solidification. The new technique is shown to have wide potential for metallurgical and materials science applications where the dynamics of elemental re-distribution and segregation in complex alloys is of importance.

3D chemical imaging in the laboratory by hyperspectral X-ray computed tomography.

We report the development of laboratory based hyperspectral X-ray computed tomography which allows the internal elemental chemistry of an object to be reconstructed and visualised in three dimensions. The method employs a spectroscopic X-ray imaging detector with sufficient energy resolution to distinguish individual elemental absorption edges. Elemental distributions can then be made by K-edge subtraction, or alternatively by voxel-wise spectral fitting to give relative atomic concentrations. We demonstrate its application to two material systems: studying the distribution of catalyst material on porous substrates for industrial scale chemical processing; and mapping of minerals and inclusion phases inside a mineralised ore sample. The method makes use of a standard laboratory X-ray source with measurement times similar to that required for conventional computed tomography.

The use of 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine (4-DAMP mustard) for estimating the apparent affinities of some agonists acting at muscarinic receptors in guinea-pig ileum.

1. 4-Diphenylacetoxy-N-(2-chloroethyl)-piperidine (4-DAMP mustard), which is known to block muscarinic M3 receptors in preference to muscarinic M2 receptors, was used to estimate the apparent affinity constants of some agonists acting at muscarinic receptors in guinea-pig ileum. Estimates for carbachol and n-pentyl-trimethyl ammonium iodide were similar to published values obtained in similar conditions: those for n-hexyl-trimethyl ammonium iodide were slightly lower. 2. The results for the agonists, n-pentyl- and n-hexyl-trimethyl ammonium iodides and for the partial agonist, n-heptyl-trimethyl ammonium iodide were not as regular as was suggested by Stephenson, though there is an overall increase in apparent affinity with chain length. 3. Estimates of apparent affinity may be affected by hexamethonium, usually present in experiments on ileum. Its absence had little effect on the results with carbachol but reduced the estimates obtained with n-pentyl trimethyl ammonium, which has strong nicotinic effects compared with its muscarinic effects. On ileum treated with tetrodotoxin the values for n-pentyl trimethyl ammonium were similar to those obtained in the presence of hexamethonium (0.28 mM): slightly higher estimates of affinity were obtained in the presence of indomethacin (2.8 microM). The nicotinic effects of n-pentyl ammonium may involve the release of prostaglandins. 4. The estimates of apparent affinity did not depend on the method used to calculate them as the 'null' method and the 'operational' method give similar answers. Estimates of the transducer-ratio for the partial agonist, n-heptyl-trimethyl ammonium iodide, were numerically the same as those of its efficacy. 5. This work illustrates the use of 4-DAMP mustard as a tool for measuring the apparent affinity of agonists acting at muscarinic M3 receptors.

The affinity of some acetylenic analogues of 4-DAMP methobromide for muscarinic receptors in guinea-pig ileum and atria.

1. The replacement of 4-hydroxy-N-methyl piperidine (HO NMe) in 4-diphenylacetoxy-N-methyl piperidine (4-DAMP) metho-bromide by 4-hydroxy-but-2-ynylamines (HOCH2C=CCH2NR2) reduces the affinity for muscarine-sensitive acetylcholine receptors in guinea-pig ileum and atria. It does not abolish selectivity. The tertiary amines are more active and more selective than the corresponding quaternary salts. 2. Analogous derivatives of 4-hydroxy-but-2-ynylamines which lack the ester group (i.e. substituted 4-hydroxymethyl-propynyl amines) are less active and less selective. The quaternary compounds are more active than the tertiary bases. 3. The diphenylcarbamyl ester of 4-hydroxy-N-methylpiperidine methobromide has less than one-thousandth of the activity of the diphenylacetyl ester (4-DAMP methobromide) and is not selective. 4. Although 4-diphenylacetoxy-butynyl dimethylamine is only about one-hundredth as active as 4-DAMP methobromide it appears to have comparable selectivity. It is an interesting compound because it is a tertiary amine and should cross membranes.

Effects of chain-length and unsaturation on affinity and selectivity at muscarinic receptors.

1. Lengthening the chain in diphenylacetylcholine decreases affinity for muscarinic cholinoceptors in guinea-pig ileum. Diphenylacetoxypropyldimethylamine and its quaternary trimethylammonium salt are roughly equiactive: the dimethylamine and the piperidine have some selectivity for ileum compared with atria, but are not as active nor as selective as 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) methobromide (MeBr). With the weaker diphenylacetoxybutyl compounds the base is more active than the quaternary salt. 2. The diphenylacetoxybutyl-, cis-butenyl and trans-butenyl compounds have similar affinities. The quaternary salts are less active than the tertiary bases, but they are less selective than the butynyl analogues studied in earlier work. 3. 1,1-Diphenyl-1-hydroxy-2,4-hexadiynyl dimethylamine and its trimethylammonium salt are inactive in concentrations below 100 microM, as are the (+)-camphor-sulphonyl ester of 4-hydroxy-N-methyl piperidine and its methiodide. The (+/-)-phenylcyclopentylacetyl ester of 4-hydroxy-N-methylpiperidine methobromide is more active than its cyclohexyl analogue and than 4-DAMP MeBr but it is less selective than 4-DAMP MeBr. 4. The high selectivity of p-fluoro-hexahydrosila-diphenidol is confirmed but this compound has relatively low affinity (for ileum log K = 7.8). 5. The results indicate steric constraints to binding at muscarinic receptors which could be used to check molecular modelling of the receptor based on its known amino acid sequence. The group binding the charged nitrogen is probably at the mouth of a cavity which can accommodate two large rings (as in 4-DAMP MeBr) but with a depth less than about 7 A so that the rod-like hexadiynes cannot fit. Differences between types of receptor may only involve small changes in geometry secondary to differences in amino acids not directly involved in binding and the production of selectivity depends upon finding substituents which interfere with binding more at one type of receptor than at another.

The contribution of charge to affinity at functional (M3) muscarinic receptors in guinea-pig ileum assessed from the effects of the carbon analogue of 4-DAMP methiodide.

1. 4-Diphenylacetoxy-1:1-dimethyl cyclohexane (carbo-4-DAMP) is the carbon analogue of 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) methiodide. The compounds differ only in that the quaternary nitrogen atom in 4-DAMP methiodide is replaced by a quaternary carbon atom, which is uncharged. 2. Carbo-4-DAMP appears to act competitively at functional (M3) muscarinic receptors in guinea-pig ileum. Estimates of log affinity constant are 6.0 at 30 degrees C and 5.9 at 37 degrees C, i.e. the compound has 0.1% of the affinity of 4-DAMP methobromide. 3. The absence of charge makes little difference to the conformation as determined by X-ray crystallography. The bond lengths and angles are very similar, though the bonds in the cyclohexane ring of carbo-4-DAMP are consistently slightly longer than those in the piperidinium ring of 4-DAMP methiodide, and the presence of the charge slightly reduces the space between molecules. 4. The difference between the affinities of 4-DAMP methobromide and carbo-4-DAMP indicates that the contribution of coulombic forces to the binding between 4-DAMP methiodide and muscarinic (M3) receptors is at least 17 kJ mol-1 (4.1 kcal mol-1) at 37 degrees C. How much this is an underestimate depends upon how much hydrophobic binding is greater with the uncharged compound.

Some differential effects of 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride on guinea-pig atria and ileum.

4-Diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride (I) cyclizes at neutral pH to form an aziridinium salt. The formation and breakdown of the salt depend on the temperature (in the range 25 to 37 degrees C). In solution at 30 degrees C, peak levels, corresponding to 60-80% conversion, are reached after around 60 min and the half-life exceeds 100 min. In the presence of 0.9% NaCl conversion was reduced to 45-60%. I blocks muscarinic receptors in guinea-pig ileum and atria irreversibly and it is possible to produce dose-ratios on ileum with 10 nM I which are about 100 times those on atria. After about 30 min exposure to solutions of I (prepared 15-20 min previously so that formation of aziridinium ions is well-established) the graph of log (dose-ratio) against time is linear and similar plots were obtained with two different agonists, carbachol and ethoxyethyltrimethylammonium. With results for the ileum, extrapolation of the line suggests that it does not start from zero (dose-ratio = 1): this is because of an initial relatively rapid reversible block. This early phase is similar to that seen on ileum with 10 nM 4DAMP methobromide, which is a competitive antagonist, so is probably caused by competitive block by the aziridinium ion, which closely resembles 4DAMP metho-salts. The subsequent irreversible phase should be caused by alkylation of the receptors. I is easy to make and should be a valuable tool for the study of muscarinic receptors.

Pixellated Cd(Zn)Te high-energy X-ray instrument.

We have developed a pixellated high energy X-ray detector instrument to be used in a variety of imaging applications. The instrument consists of either a Cadmium Zinc Telluride or Cadmium Telluride (Cd(Zn)Te) detector bump-bonded to a large area ASIC and packaged with a high performance data acquisition system. The 80 by 80 pixels each of 250 µm by 250 µm give better than 1 keV FWHM energy resolution at 59.5 keV and 1.5 keV FWHM at 141 keV, at the same time providing a high speed imaging performance. This system uses a relatively simple wire-bonded interconnection scheme but this is being upgraded to allow multiple modules to be used with very small dead space. The readout system and the novel interconnect technology is described and how the system is performing in several target applications.

Ex vivo monitoring of human cytomegalovirus-specific CD8+ T-cell responses using QuantiFERON-CMV.

We have developed a novel diagnostic technology to monitor the human cytomegalovirus (HCMV)-specific CD8+ T-cell responses that is based on the detection of secreted interferon-gamma (IFN-gamma) in the whole blood (referred to as QuantiFERON -CMV). Evaluation of QuantiFERON -CMV in healthy individuals revealed that this technology was at least as sensitive and with some HCMV epitopes more sensitive than the ELISPOT for detecting ex vivo IFN-gamma. Results from QuantiFERON -CMV assays showed 97% (36/37 individuals) agreement with the anti-HCMV serology test in healthy individuals. Furthermore, we also show that this technology can be used to assess HCMV-specific T-cell responses in transplant patients. This study shows that QuantiFERON -CMV is a simple, reproducible, and reliable test for the detection of IFN-gamma in response to HCMV CD8+ T-cell epitopes, and may be a valuable diagnostic test for the detection of HCMV infection and a useful clinical tool for monitoring the immune response in immunosuppressed patients during therapy.

Mechanical simulation of renal pelvic wall peristalsis in the rat.

A urinary concentrating defect was induced in Munich-Wistar rats by removing the renal pelvis from 1 kidney. This defect was partially corrected by crudely simulating the actions of pelvic wall peristalsis with a mechanical system that cyclically compressed the exposed renal papilla.

The prevalence of hypertension in urban whites.

In a random house-to-house study of 1006 Whites the prevalence of primary hypertension according to World Health Organization criteria was 22,76% (25,6% of males, 20% of females). This is lower than the prevalence in our study of urban Zulus and higher than that in our study of urban Indians. The study also revealed that the prevalence of hypertension was higher than in Whites in the USA. The prevalence in males aged under 40 years was twice that in females of the same age. Blood pressure rose with age, and there was a greater rise in systolic than in diastolic blood pressure. The rise was more marked in males over the age of 40 years and in females over the age of 60 years. Mean systolic and diastolic blood pressures were higher in the male urban Whites than in males in our Zulu and Indian studies and lower than in females in our Zulu and Indian studies. The high prevalence of diastolic blood pressures of 105 mmHg or more, together with the high prevalence of hypertension in White male subjects aged under 40 years, could be an important factor in the aetiology of ischaemic heart disease in White males in the 25-34-year age greup. In our White study only 23% of the hypertensive subjects were on therapy. More effective screening and therapeutic programmes should therefore be initiated in the White population because of the high prevalence of hypertension which may lead to complications.

Involvement of adenosine in ethanol-induced changes in G-protein expression in NG108-15 cells?

Previous work has suggested that adenosine may be involved in ethanol-induced heterologous desensitization of adenylate cyclase in NG108-15 cells. It was proposed that chronic ethanol causes adenosine to accumulate extracellularly, activating adenosine A2 receptors and so leading to a reduction in Gs alpha mRNA and Gs alpha protein (Nagy et al., 1989). In this study we further investigated the effect of chronic ethanol on G-protein expression in NG108-15 cells. Pretreatment of NG108-15 cells with ethanol (200 mM, 48h) reduced membrane levels of Gs alpha and Gi alpha but increased Go alpha expression. The effects of ethanol on alpha-subunit expression were not reversed by adenosine deaminase and could not be mimicked by the adenosine agonist 5'- (n-ethyl)-carboxamidoadenosine (NECA). Chronic ethanol pretreatment did not appear to reduce the levels of Gs alpha or Gi alpha 2 mRNA. This same ethanol pretreatment reduced cell proliferation and increased differentiation without altering cell viability. Adenosine deaminase did not reverse any of these effects. These results indicate that ethanol differentially regulates G-protein alpha-subunit expression and induces morphological alterations in these cells independently of extracellular adenosine.