Laser cooling of antihydrogen atoms.

The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision1. Slowing the translational motion of atoms and ions by application of such a force2,3, known as laser cooling, was first demonstrated 40 years ago4,5. It revolutionized atomic physics over the following decades6-8, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen9, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation10,11, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic11-13 and gravitational14 studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.

Observation of the 1S-2P Lyman-α transition in antihydrogen.

In 1906, Theodore Lyman discovered his eponymous series of transitions in the extreme-ultraviolet region of the atomic hydrogen spectrum1,2. The patterns in the hydrogen spectrum helped to establish the emerging theory of quantum mechanics, which we now know governs the world at the atomic scale. Since then, studies involving the Lyman-α line-the 1S-2P transition at a wavelength of 121.6 nanometres-have played an important part in physics and astronomy, as one of the most fundamental atomic transitions in the Universe. For example, this transition has long been used by astronomers studying the intergalactic medium and testing cosmological models via the so-called 'Lyman-α forest'3 of absorption lines at different redshifts. Here we report the observation of the Lyman-α transition in the antihydrogen atom, the antimatter counterpart of hydrogen. Using narrow-line-width, nanosecond-pulsed laser radiation, the 1S-2P transition was excited in magnetically trapped antihydrogen. The transition frequency at a field of 1.033 tesla was determined to be 2,466,051.7 ± 0.12 gigahertz (1σ uncertainty) and agrees with the prediction for hydrogen to a precision of 5 × 10-8. Comparisons of the properties of antihydrogen with those of its well-studied matter equivalent allow precision tests of fundamental symmetries between matter and antimatter. Alongside the ground-state hyperfine4,5 and 1S-2S transitions6,7 recently observed in antihydrogen, the Lyman-α transition will permit laser cooling of antihydrogen8,9, thus providing a cold and dense sample of anti-atoms for precision spectroscopy and gravity measurements10. In addition to the observation of this fundamental transition, this work represents both a decisive technological step towards laser cooling of antihydrogen, and the extension of antimatter spectroscopy to quantum states possessing orbital angular momentum.

Characterization of the 1S-2S transition in antihydrogen.

In 1928, Dirac published an equation 1 that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron 2 (or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter3-7, including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed 8 in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 × 1015 hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 × 10-12-two orders of magnitude more precise than the previous determination 8 -corresponding to an absolute energy sensitivity of 2 × 10-20 GeV.

Performance Scaling in Magnetized Liner Inertial Fusion Experiments.

We present experimental results from the first systematic study of performance scaling with drive parameters for a magnetoinertial fusion concept. In magnetized liner inertial fusion experiments, the burn-averaged ion temperature doubles to 3.1 keV and the primary deuterium-deuterium neutron yield increases by more than an order of magnitude to 1.1×10^{13} (2 kJ deuterium-tritium equivalent) through a simultaneous increase in the applied magnetic field (from 10.4 to 15.9 T), laser preheat energy (from 0.46 to 1.2 kJ), and current coupling (from 16 to 20 MA). Individual parametric scans of the initial magnetic field and laser preheat energy show the expected trends, demonstrating the importance of magnetic insulation and the impact of the Nernst effect for this concept. A drive-current scan shows that present experiments operate close to the point where implosion stability is a limiting factor in performance, demonstrating the need to raise fuel pressure as drive current is increased. Simulations that capture these experimental trends indicate that another order of magnitude increase in yield on the Z facility is possible with additional increases of input parameters.

What has been the impact of the Traditional Herbal Registration (THR) scheme in the UK on information provided with herbal products bought over the counter?

BACKGROUND: In 2011 there was a strengthening of European Union (EU) legislation on the licencing of herbal products which, in the UK, resulted in the introduction of the Traditional Herbal Registration (THR) scheme. This scheme sets out standards for the safety and quality of herbal medicines and includes the provision of information to the customer on the safe use of the product. The aim of this study is to replicate a survey undertaken in 2011, prior to the implementation of the THR scheme, and evaluate the impact of this scheme on the information provided with herbal products bought over-the-counter. METHODS: We undertook a survey on 5 herbal products commonly available over-the-counter (St John's wort, echinacea, Ginkgo biloba, Asian ginseng, garlic). The information was searched for key safety messages identified by the National Center for Complementary and Integrative Health (NCCIH). We also explored the presence of risk of harm information. RESULTS: We recorded a rise in the number of products registered with the THR scheme (37% in 2016 compared to 7% in 2011). We also identified a reduction in the number of products that did not contain key safety information (75% in 2011 compared to 20% of products obtained in 2016). Risk of harm information was only communicated in products containing a PIL. We identified more products containing frequency of risk of harm information but this was not statistically significant. CONCLUSION: The introduction of the THR scheme appears to be associated with an increase in the provision of information about key safety messages on the safe use of herbal products. However, it is important to note that at least half of the products on the market that are not included in the THR scheme do not contain any information about their safe use; this includes information about precautions, interactions and side effects. The use of NCCIH herbal monographs replicated the methods used in the previous study; we recognise that the use of a different resource might effect the appraisal of the information provided. We also acknowledge that surveying presence of information does not assure that the latter is effectively communicated to patients, for which a close textual analysis would be required. While it is promising that more information is available after the introduction of the THR scheme, the public needs to be informed about ways to optimise safe use of all herbal products.

A 400-year reconstruction of wintertime Arctic sea-ice extent using a high-elevation, mid-latitude tree-ring record.

We examined relationships between wintertime Arctic sea-ice extent (ASIE) and radial growth rates of alpine larch trees (LALY) in the northern Rockies, USA, during 1979-2015 (r = - 0.71, p < 0.01) and reconstructed ASIE fluctuations from 1613 to 2015. Wintertime ASIE corresponds with summertime mid-latitude upper-level atmospheric flow patterns with ridging (troughing) and warmer (cooler) conditions prevailing in the Rockies when ASIE are below (above) average. In turn, warmer (cooler) summertime conditions favor (disfavor) growth of LALY, thus "recording" interannual variations in ASIE. Both 1000 hPa temperatures and 500 hPa geopotential heights during years of anomalously high or low radial growth negatively correspond with ASIE, suggesting that a disjunct spatial influence on atmospheric conditions may be associated with interannual variability of ASIE. Reconstructed ASIE values show that 1996-2015 was the lowest 20-year period on record, but the mean value is not significantly different from six other distinct periods of below-average ASIE.

Experimental demonstration of fusion-relevant conditions in magnetized liner inertial fusion.

This Letter presents results from the first fully integrated experiments testing the magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)], in which a cylinder of deuterium gas with a preimposed 10 Taxial magnetic field is heated by Z beamlet, a 2.5 kJ, 1 TW laser, and magnetically imploded by a 19 MA, 100 ns rise time current on the Z facility. Despite a predicted peak implosion velocity of only 70 km = s, the fuel reaches a stagnation temperature of approximately 3 keV, with T(e) ≈ T(i), and produces up to 2 x 10(12) thermonuclear deuterium-deuterium neutrons. X-ray emission indicates a hot fuel region with full width at half maximum ranging from 60 to 120 µm over a 6 mm height and lasting approximately 2 ns. Greater than 10(10) secondary deuterium-tritium neutrons were observed, indicating significant fuel magnetization given that the estimated radial areal density of the plasma is only 2 mg = cm(2).

Understanding fuel magnetization and mix using secondary nuclear reactions in magneto-inertial fusion.

Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during deuterium-deuterium fusion and can undergo secondary deuterium-tritium reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall deuterium-tritium to deuterium-deuterium neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions also are shown to provide an upper bound for the volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs.

Advanced data analysis in inertial confinement fusion and high energy density physics.

Bayesian analysis enables flexible and rigorous definition of statistical model assumptions with well-characterized propagation of uncertainties and resulting inferences for single-shot, repeated, or even cross-platform data. This approach has a strong history of application to a variety of problems in physical sciences ranging from inference of particle mass from multi-source high-energy particle data to analysis of black-hole characteristics from gravitational wave observations. The recent adoption of Bayesian statistics for analysis and design of high-energy density physics (HEDP) and inertial confinement fusion (ICF) experiments has provided invaluable gains in expert understanding and experiment performance. In this Review, we discuss the basic theory and practical application of the Bayesian statistics framework. We highlight a variety of studies from the HEDP and ICF literature, demonstrating the power of this technique. Due to the computational complexity of multi-physics models needed to analyze HEDP and ICF experiments, Bayesian inference is often not computationally tractable. Two sections are devoted to a review of statistical approximations, efficient inference algorithms, and data-driven methods, such as deep-learning and dimensionality reduction, which play a significant role in enabling use of the Bayesian framework. We provide additional discussion of various applications of Bayesian and machine learning methods that appear to be sparse in the HEDP and ICF literature constituting possible next steps for the community. We conclude by highlighting community needs, the resolution of which will improve trust in data-driven methods that have proven critical for accelerating the design and discovery cycle in many application areas.

X-ray self-emission imaging with spherically bent Bragg crystals on the Z-machine.

An x-ray imaging scheme using spherically bent crystals was implemented on the Z-machine to image x rays emitted by the hot, dense plasma generated by a Magnetized Liner Inertial Fusion (MagLIF) target. This diagnostic relies on a spherically bent crystal to capture x-ray emission over a narrow spectral range (<15 eV), which is established by a limiting aperture placed on the Rowland circle. The spherical crystal optic provides the necessary high-throughput and large field-of-view required to produce a bright image over the entire, one-cm length of the emitting column of a plasma. The average spatial resolution was measured and determined to be 18 µm for the highest resolution configuration. With this resolution, the radial size of the stagnation column can be accurately determined and radial structures, such as bifurcations in the column, are clearly resolved. The success of the spherical-crystal imager has motivated the implementation of a new, two-crystal configuration for identifying sources of spectral line emission using a differential imaging technique.

A generalized approach to x-ray data modeling for high-energy-density plasma experiments.

Accurate understanding of x-ray diagnostics is crucial for both interpreting high-energy-density experiments and testing simulations through quantitative comparisons. X-ray diagnostic models are complex. Past treatments of individual x-ray diagnostics on a case-by-case basis have hindered universal diagnostic understanding. Here, we derive a general formula for modeling the absolute response of non-focusing x-ray diagnostics, such as x-ray imagers, one-dimensional space-resolved spectrometers, and x-ray power diagnostics. The present model is useful for both data modeling and data processing. It naturally accounts for the x-ray crystal broadening. The new model verifies that standard approaches for a crystal response can be good approximations, but they can underestimate the total reflectivity and overestimate spectral resolving power by more than a factor of 2 in some cases near reflectivity edge features. We also find that a frequently used, simplified-crystal-response approximation for processing spectral data can introduce an absolute error of more than an order of magnitude and the relative spectral radiance error of a factor of 3. The present model is derived with straightforward geometric arguments. It is more general and is recommended for developing a unified picture and providing consistent treatment over multiple x-ray diagnostics. Such consistency is crucial for reliable multi-objective data analyses.

Demonstration of improved laser preheat with a cryogenically cooled magnetized liner inertial fusion platform.

We report on progress implementing and testing cryogenically cooled platforms for Magnetized Liner Inertial Fusion (MagLIF) experiments. Two cryogenically cooled experimental platforms were developed: an integrated platform fielded on the Z pulsed power generator that combines magnetization, laser preheat, and pulsed-power-driven fuel compression and a laser-only platform in a separate chamber that enables measurements of the laser preheat energy using shadowgraphy measurements. The laser-only experiments suggest that ∼89% ± 10% of the incident energy is coupled to the fuel in cooled targets across the energy range tested, significantly higher than previous warm experiments that achieved at most 67% coupling and in line with simulation predictions. The laser preheat configuration was applied to a cryogenically cooled integrated experiment that used a novel cryostat configuration that cooled the MagLIF liner from both ends. The integrated experiment, z3576, coupled 2.32 ± 0.25 kJ preheat energy to the fuel, the highest to-date, demonstrated excellent temperature control and nominal current delivery, and produced one of the highest pressure stagnations as determined by a Bayesian analysis of the data.

Reversed glucose and fatty acids transporter expression in human endometrial cancer.

Cancer cells exhibit accelerated rates of metabolism favoring glucose over fatty acid (FA) utilization. For both energy substrates, protein-mediated transport plays an essential role in facilitating glucose or FA movement across plasma membrane into the cells. Scarce data exist regarding the expression of glucose and/or FA transporter in cancer tissue. Therefore, we examined glucose (GLUT-1, GLUT-3, GLUT-4) and FA (FAT/CD36, FABPpm, FATP-1) transporter expressions at the protein and post-transcript (mRNA) levels in 35 endometrial carcinomas (G1, type endometrioid, FIGO I) and compared them with normal endometrial mucosa (n=10). Endometrial cancer tissue had significantly greater protein expression of GLUT-1, GLUT-3, and GLUT-4 (+ 40%; + 20%; + 24%; p<0.05, respectively) and, conversely, lower fatty acid (FAT/CD36 and FATP-1) transporter expression ( - 25%; p<0.05 and - 15%, p>0.05 respectively). Interestingly, mRNA content closely mirrors the changes, but only for glucose transporters and not fatty acid transporters. These results suggest the presence of metabolic switch of energy utilization in endometrial cancers favoring glucose consumption as the major source of energy.

Factors affecting response of chemotherapy in women with ovarian cancer.

Chemotherapy plays an important role in the treatment of ovarian cancer. Patients' response to chemotherapy is determined by a variety of acknowledged factors, but one might expect that many of them are yet to be described. The aim of this paper was to present the most essential yet still to be generally assessed in clinical practice, factors, which include: E-cadhedrin, hypoxia inducible factor alpha, survivin, COX-2, clusterin, BRCA1 protein, TP53 protein, YY1 protein, multidrug resistance protein, and interleukin-8.

Activation of the caspase-3 apoptotic cascade in traumatic spinal cord injury.

Traumatic spinal cord injury often results in complete loss of voluntary motor and sensory function below the site of injury. The long-term neurological deficits after spinal cord trauma may be due in part to widespread apoptosis of neurons and oligodendroglia in regions distant from and relatively unaffected by the initial injury. The caspase family of cysteine proteases regulates the execution of the mammalian apoptotic cell death program. Caspase-3 cleaves several essential downstream substrates involved in the expression of the apoptotic phenotype in vitro, including gelsolin, PAK2, fodrin, nuclear lamins and the inhibitory subunit of DNA fragmentation factor. Caspase-3 activation in vitro can be triggered by upstream events, leading to the release of cytochrome c from the mitochondria and the subsequent transactivation of procaspase-9 by Apaf-1. We report here that these upstream and downstream components of the caspase-3 apoptotic pathway are activated after traumatic spinal cord injury in rats, and occur early in neurons in the injury site and hours to days later in oligodendroglia adjacent to and distant from the injury site. Given these findings, targeting the upstream events of the caspase-3 cascade has therapeutic potential in the treatment of acute traumatic injury to the spinal cord.

Converting existing optical detectors into fast x-ray detectors.

The very short burn time and small size of burning plasmas created at advanced laser-fusion facilities will require high-spatial-resolution imaging diagnostics with fast time resolution. These instruments will need to function in an environment of extremely large neutron fluxes that will cause conventional diagnostics to fail because of radiation damage and induced background levels. One solution to this challenge is to perform an ultrafast conversion of the x-ray signals into the optical regime before the neutrons are able to reach the detector and then to relay image the signal out of the chamber and into a shielded bunker, protected from the effects of these neutrons. With this goal in mind, the OMEGA laser was used to demonstrate high-temporal-resolution x-ray imaging by using an x-ray snout to image an imploding backlighter capsule onto a semiconductor. The semiconductor was simultaneously probed with the existing velocity interferometry system for any surface reflector (VISAR) diagnostic, which uses an optical streak camera and provided a one-dimensional image of the phase in the semiconductor as a function of time. The phase induced in the semiconductor was linearly proportional to the x-ray emission from the backlighter capsule. This approach would then allow a sacrificial semiconductor to be attached at the end of an optical train with the VISAR and optical streak camera placed in a shielded bunker to operate in a high neutron environment and obtain time-dependent one-dimensional x-ray images or time-dependent x-ray spectra from a burning plasma.

Cellular dimensions affecting the nucleocytoplasmic volume ratio.

Although it has long been appreciated that larger eukaryotic cells have larger nuclei, little is known about how this size relationship is maintained. Here we describe a method for measuring the aqueous volume ratio of nucleus to cytoplasm, two compartments which are interconnected via the pores in the nuclear envelope. We then use that method to identify proportional cellular dimensions in variously treated cells and in different cell types. Cells were scrape loaded with a mixture of fluorescent dextrans: Texas red dextran, average mol wt = 10,000 (TRDx10), and fluorescein isothiocyanate dextran, average mol wt = 70,000 (FDx70). After introduction into the cytoplasmic space, the TRDx10 distributed into both the nucleus and cytoplasm, whereas the FDx70 was restricted to cytoplasm, due to size exclusion by the nuclear pores. The aqueous nucleocytoplasmic volume ratio (RN/C) was determined by measuring, from fluorescence images of spread cells, total cellular fluorescence of each of the two probes and the fluorescence ratio of those probes in the cytoplasm. RN/C was unaffected by the measurement procedure or by varying temperatures between 23 degrees and 37 degrees C. Loading excess unlabeled dextrans had little effect on RN/C, with the single exception that high concentrations of large dextrans could lower RN/C in endothelial cells. Expanding intracellular membranous compartments of macrophages by phagocytosis of latex beads decreased RN/C. Expanding the same compartment by pinocytosis of sucrose, which nearly doubled total cell volume, had little effect on RN/C, indicating that nuclear volume was more closely linked to the cytoplasmic volume, exclusive of vesicular organelles, than to total cell volume. RN/C was the same in mononucleate and binucleate endothelial cells. Finally, measurements of RN/C in murine bone marrow-derived macrophages, bovine aortic endothelial cells, Swiss 3T3 fibroblasts, PtK2 cells, and CV-1 cells revealed that nuclear volume scaled allometrically with cell volume. The allometric relationship indicated that cell volume was proportional to nuclear surface area.

Performance-based readability testing of participant materials for a phase I trial: TGN1412.

BACKGROUND: Concern has been expressed about the process of consent to clinical trials, particularly in phase I "first-in-man" trials. Trial participant information sheets are often lengthy and technical. Content-based readability testing of sheets, which is often required to obtain research ethics approval for trials in the USA, is limited and cannot indicate how information will perform. METHODS: An independent-groups design was used to study the user-testing performance of the participant information sheet from the phase I TGN1412 trial. Members of the public were asked to read it, then find and demonstrate understanding of 21 key aspects of the trial. The participant information sheet was then rewritten, redesigned and tested on 20 members of the public, using the same 21-item questionnaire. RESULTS: On the original TGN1412 participant information sheet, participants could not find answers and some of the found information was not understood. Six of 21 questions, including those relating to placebo, follow-up visits and the emergency phone number, were found by eight or fewer of 10 participants. The revised information sheet performed better, with the answers to 17 of 21 questions found and understood by all 20 participants. CONCLUSIONS: Tests showed that the TGN1412 participant information sheet may not inform participants adequately for consent. Revising its content and design led to significant improvements. Writers of materials for trial participants should take account of good practice in information design. Performance-based user testing may be a useful method to indicate strengths and weaknesses in trial materials.

Perceived risk of medicine side effects in users of a patient information website: a study of the use of verbal descriptors, percentages and natural frequencies.

OBJECTIVES: Research into the provision of patient information has demonstrated that, under certain conditions, patients overestimate the risks of medicine side effects. Gigerenzer and Edwards (2004) argue that 'natural frequencies' are a less confusing way of expressing risk information. Two experiments with users of an existing high profile patient information website, investigate the effectiveness of presenting medicine side-effect risk information in different forms. DESIGN: In both experiments participants were randomly allocated to one of the three conditions for representing risk information (a form of 'natural frequency', percentages and verbal descriptors). METHOD: Participants were recruited from users of the Cancer Research UK patient information website (Cancer Help UK). In Experiment 1, participants (N=148) were asked to imagine that they had to take a chemotherapy drug (Taxol) and were asked to estimate the risks of two side-effects occurring. In Experiment 2 participants (N=137) estimated the risk for three different side-effects occurring with the painkiller ibuprofen. RESULTS: In both experiments, verbal descriptions led to significantly higher estimations of risk compared to the other two formats. There was some evidence that people given information as frequencies were more accurate in their estimates than those given percentage information. CONCLUSIONS: These findings provide partial support for the advantages of a form of 'natural frequencies' when presenting side-effects to patients. They also add weight to the growing body of research highlighting the deficiencies in using verbal descriptions of side-effect risk alone.

Information provision for stroke patients and their caregivers.

BACKGROUND: Research shows that stroke patients and their families are dissatisfied with the information provided and have a poor understanding of stroke and associated issues. OBJECTIVES: To assess the effectiveness of information provision strategies in improving the outcome for stroke patients and/or their identified caregivers. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched May 2007), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2007), MEDLINE (1966 to March 2007), EMBASE (1980 to March 2007), CINAHL (1982 to March 2007), PsycINFO (1974 to March 2007), Science Citation Index and Social Science Citation Index (1981 to March 2007), Assia (1987 to March 2007), Index to UK theses (1970 to March 2007), Dissertation Abstracts (1961 to March 2007), ongoing trials and research registers, bibliographies of retrieved papers, relevant articles and books, and the Journal of Advanced Nursing. We also contacted researchers for additional information. SELECTION CRITERIA: Randomised trials involving patients or carers of patients with a clinical diagnosis of stroke or transient ischaemic attack (TIA) where an information intervention was compared with standard care, or where information and another therapy were compared with the other therapy alone. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trial eligibility and methodological quality and extracted data. Primary outcomes were knowledge about stroke and stroke services, and impact on mood. MAIN RESULTS: Seventeen trials involving 1773 patient and 1058 carer participants were included. Eight evaluated a passive and nine an active information intervention. Meta-analyses showed a significant effect in favour of the intervention on patient and carer knowledge, one aspect of patient satisfaction, and patient depression scores. There was no significant effect on number of cases of anxiety or depression in patients, carer mood or satisfaction, or death. Qualitative analyses found no strong evidence of an effect on other outcomes. Post-hoc subgroup analyses showed that active information had a significantly greater effect than passive information on patient mood but not on other outcomes. AUTHORS' CONCLUSIONS: There is evidence that information improves patient and carer knowledge of stroke, aspects of patient satisfaction, and reduces patient depression scores. However, the reduction in depression scores was small and probably clinically insignificant. Although the best way to provide information is still unclear there is some evidence that strategies that actively involve patients and carers and include planned follow up for clarification and reinforcement have a greater effect on patient mood.