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Using a millimetre-wave molecular line scan, a redshift has finally been determined for the extremely active star-forming galaxy HDF 850.1 in the Hubble Deep Field, which makes it younger than thought at 1.1 billion years after the Big Bang. Starburst object HDF 850.1 retains some mystery The brightest sub-millimetre radio source in the Hubble Deep Field view of the distant Universe, known as HDF 850.1, has proved enigmatic, evading detection in the optical and near-infrared ranges despite an intensive search. Without the discovery of a counterpart at shorter wavelengths, it has not been possible to estimate the source's redshift, size or mass directly. Now, by using a millimetre-wave molecular line scan, the redshift of HDF 850.1 has been determined. At z ≈ 5.2, it is much higher than expected and corresponds to a cosmic age of only 1.1 billion years after the Big Bang. Calculations from the new data suggest a high annual star formation rate of 850 solar masses and a mass of 1.3 × 10 11 solar masses. But as yet there is no sign of a starlight-emitting counterpart. The Hubble Deep Field provides one of the deepest multiwavelength views of the distant Universe and has led to the detection of thousands of galaxies seen throughout cosmic time 1 . An early map of the Hubble Deep Field at a wavelength of 850 micrometres, which is sensitive to dust emission powered by star formation, revealed the brightest source in the field, dubbed HDF 850.1 (ref. 2 ). For more than a decade, and despite significant efforts, no counterpart was found at shorter wavelengths, and it was not possible to determine its redshift, size or mass 3 , 4 , 5 , 6 , 7 . Here we report a redshift of z = 5.183 for HDF 850.1, from a millimetre-wave molecular line scan. This places HDF 850.1 in a galaxy overdensity at z  ≈ 5.2, corresponding to a cosmic age of only 1.1 billion years after the Big Bang. This redshift is significantly higher than earlier estimates 3 , 4 , 6 , 8 and higher than those of most of the hundreds of submillimetre-bright galaxies identified so far. The source has a star-formation rate of 850 solar masses per year and is spatially resolved on scales of 5 kiloparsecs, with an implied dynamical mass of about 1.3 × 10 11 solar masses, a significant fraction of which is present in the form of molecular gas. Despite our accurate determination of redshift and position, a counterpart emitting starlight remains elusive.

The autoimmune disease systemic sclerosis (SSc) causes microvascular changes that can be easily observed cutaneously at the finger nailfold. Optoacoustic imaging (OAI), a combination of optical and ultrasound imaging, specifically raster-scanning optoacoustic mesoscopy (RSOM), offers a non-invasive high-resolution 3D visualization of capillaries allowing for a better view of microvascular changes and an extraction of volumetric measures. In this study, nailfold capillaries of patients with SSc and healthy controls are imaged and compared with each other for the first time using OAI. The nailfolds of 23 patients with SSc and 19 controls were imaged using RSOM. The acquired images were qualitatively compared to images from state-of-the-art imaging tools for SSc, dermoscopy and high magnification capillaroscopy. The vascular volume in the nailfold capillaries were computed from the RSOM images. The vascular volumes differ significantly between both cohorts (0.216 ± 0.085 mm 3 and 0.337 ± 0.110 mm 3 ; p < 0.0005). In addition, an artificial neural network was trained to automatically differentiate nailfold images from both cohorts to further assess whether OAI is sensitive enough to visualize anatomical differences in the capillaries between the two cohorts. Using transfer learning, the model classifies images with an area under the ROC curve of 0.897, and a sensitivity of 0.783 and specificity of 0.895. In conclusion, this study demonstrates the capabilities of RSOM as an imaging tool for SSc and establishes it as a modality that facilitates more in-depth studies into the disease mechanisms and progression.

Systemic sclerosis (SSc)-related digital ischaemia is a major cause of morbidity, resulting from a combination of microvascular and digital artery disease. Photoacoustic imaging offers a newly available, non-invasive method of imaging digital artery structure and oxygenation. The aim of this study was to establish whether photoacoustic imaging could detect and measure vasculopathy in digital arteries, including the level of oxygenation, in patients with SSc and healthy controls. 22 patients with SSc and 32 healthy controls (HC) underwent photoacoustic imaging of the fingers. Vascular volume and oxygenation were assessed across eight fingers at the middle phalanx. In addition, oxygenation change during finger occlusion was measured at the non-dominant ring finger and the vascular network was imaged along the length of one finger for qualitative assessment. There was no statistically significant difference in vascular volume between patients with SSc and HC (mean of eight fingers; SSc, median 118.6 IQR [95.0–130.5] vs. HC 115.6 [97.8–158.9]) mm 3 . However, baseline oxygenation (mean 8 fingers) was lower in SSc vs. HC (0.373 [0.361–0.381] vs. 0.381 [0.373–0.385] arbitrary sO2 units respectively; p = 0.03). Hyperaemic oxygenation response following occlusion release was significantly lower in SSc compared to HC (0.379 [0.376–0.381] vs. 0.382 [0.377–0.385]; p = 0.03). Whilst vascular volume was similar between groups, digital artery oxygenation was decreased in patients with SSc as compared to HC, indicative of functional deficit. Photoacoustic imaging offers an exciting new method to image the vascular network in patients with SSc and the possibility to capture oxygenation as a functional measure.

Correspondence to Dr Graham Dinsdale, Salford Royal NHS Foundation Trust, Salford M6 8HD, UK; graham.dinsdale@manchester.ac.uk Systemic sclerosis (SSc)-related digital ulcers (DUs) are painful and disabling,1–3 and DU burden is often the primary outcome measure in clinical trials of SSc-related digital vasculopathy.4 This is despite several studies showing a lack of agreement between rheumatologists as to what constitutes a DU.5–8 Objective outcome measures of SSc-related DUs for tracking change over time are therefore urgently required for clinical practice and research studies. The application of digital planimetry to clinical DU photographs has shown the possibility of fine-grained measurement of DU characteristics (area).9 Our aims were to (1) demonstrate the feasibility of patients with SSc-related DUs/digital lesions photographing their lesions using smartphone cameras, and (2) use digital planimetry-style software analysis on images collected from patients to measure and track lesion area as a marker of healing or progression. Handling editor Josef S Smolen Twitter @DinsdaleGraham Contributors GD is responsible for study design, data collection, data analysis, and editing and approval of manuscript.

We describe the TFIT software package to measure galaxy photometry using prior information from high‐resolution observations. Our basic methodology is similar in principle but different in detail from previous procedures for crowded field photometry. We use the spatial positions and morphologies of objects in an image with higher angular resolution to construct object templates, which are then fitted to a lower resolution image, solving for the object fluxes as free parameters. Using extensive experiments on both simulated and real data, we show that this template‐fitting method measures accurate object photometry to the limiting sensitivity of the image. In this limit, our method derives robust flux upper limits for objects fainter than the limiting image surface brightness. We describe the challenges encountered in applying this technique to real data, and methods to cope with some of them.

Optical tweezers are exciting tools with which to explore liquid crystal (LC) systems; the motion of particles held in laser traps through LCs is perhaps the only approach that allows a low Ericksen number regime to be accessed. This offers a new method of studying the microrheology associated with micrometre-sized particles suspended in LC media-and such hybrid systems are of increasing importance as novel soft-matter systems. This paper describes the microrheology experiments that are possible in nematic materials and discusses the sometimes unexpected results that ensue. It also presents observations made in the inverse system; micrometre-sized droplets of LC suspended in an isotropic medium.

Lipid peroxidation may be a marker of free-radical-mediated injury associated with Alzheimer's disease (AD). We aimed to investigate whether changes in lipid peroxidation is associated with cognitive decline in individuals with Down syndrome over a 4-year period. Thirty-two adults with DS participated in a longitudinal study with urinary isoprostane 8,12-iso-iPF2alpha (iPF2alpha) assays at baseline and four years follow-up. Informants rated their functional ability and memory function and the adults with DS attempted assessments of language skills and memory. Twenty-six individuals completed assessments of memory (Modified Memory Object Task, MOMT), adaptive behavior (ABAS), and receptive vocabulary (British Picture vocabulary, BPVS) at both time-points. Overall change in iPF2alpha level was negatively correlated with change in the MOMT score (Spearman's Rho =  -0.576, p = 0.006), i.e., increased lipid peroxidation was correlated with worse memory functioning over time. An increase of ≥ 0.02 ng/mg creatinine iPF2α had good sensitivity (85.7%), positive predictive value (75%,), specificity (85.7%) and negative predictive value (92.3%) for memory decline. Change in iPF2alpha over time may have potential as a biomarker for memory decline in Down syndrome and potentially also help to track progression of MCI to AD in the general population.

The Hubble deep fields (HDFs) continue to be a valuable resource for studying the distant Universe, particularly at z > 2 where their comoving volume becomes large enough to encompass several hundred L* galaxies or their progenitors. Here, I present recent results from a near-infrared (NIR) imaging survey of the HDFnorth with the Near Infrared Camera and Multi-Object Spectrograph (NICMOS), which provides structural and photometric information in the optical rest frame (λλ24000-5500 Å) for hundreds of 'ordinary' galaxies at 2 < z < 3, and which offers the means to search for still-more-distant objects at z > 5. Lyman-break galaxies (LBGs) at 2 < z < 3 are compact and often irregular in the NICMOS images; ordinary Hubble sequence spirals and ellipticals seem to be largely absent at these redshifts, and apparently reached maturity at 1 < z < 2. The LBGs have ultraviolet (UV)-optical spectral energy distributions like those of local starburst galaxies. Population synthesis models suggest typical ages of a few x 108 years and moderate UV extinction (ca .1.2 mag at 1700 Å), but the constraints are fairly weak and there may be considerable variety. Considering an NIR selected galaxy sample, there is little evidence for a significant number of galaxies at z 3 that have been missed by UV-based Lyman-break selection. Using the well-characterized z 3 galaxy population as a point of reference, I consider LBG candidates at 4.5 < z < 9, as well as one remarkable object that might (or might not) be an LBG at z > 12. The space density of UV-bright galaxies in the HDF appears to thin out toward larger redshifts, although surface-brightness selection effects may play an important role.

Laser trapping of particles in three dimensions can occur as a result of the refraction of strongly focused light through micrometre-sized particles. The use of this effect to produce laser tweezers is extremely common in fields such as biology, but it is only relatively recently that the technique has been applied to liquid crystals (LCs). The possibilities are exciting: droplets of LCs can be trapped, moved and rotated in an isotropic fluid medium, or both particles and defects can be trapped and manipulated within a liquid crystalline medium. This paper considers both the possibilities. The mechanism of transfer of optical angular momentum from circularly polarized light to small droplets of nematic LCs is described. Further, it is shown that droplets of chiral LCs can be made to rotate when illuminated with linearly polarized light and possible mechanisms are discussed. The trapping and manipulation of micrometre-sized particles in an aligned LC medium is used to provide a measure of local shear viscosity coefficients and a unique test of theory at low Ericksen number in LCs.