The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

The Arctic marine environment is undergoing a transition from thick multi-year to first-year sea-ice cover with coincident lengthening of the melt season. Such changes are evident in the Baffin Bay-Davis Strait-Labrador Sea (BDL) region where melt onset has occurred ~8 days decade−1 earlier from 1979 to 2015. A series of anomalously early events has occurred since the mid-1990s, overlapping a period of increased upper-air ridging across Greenland and the northwestern North Atlantic. We investigate an extreme early melt event observed in spring 2013. (~6σ below the 1981–2010 melt climatology), with respect to preceding sub-seasonal mid-tropospheric circulation conditions as described by a daily Greenland Blocking Index (GBI). The 40-days prior to the 2013 BDL melt onset are characterized by a persistent, strong 500 hPa anticyclone over the region (GBI >+1 on >75% of days). This circulation pattern advected warm air from northeastern Canada and the northwestern Atlantic poleward onto the thin, first-year sea ice and caused melt ~50 days earlier than normal. The episodic increase in the ridging atmospheric pattern near western Greenland as in 2013, exemplified by large positive GBI values, is an important recent process impacting the atmospheric circulation over a North Atlantic cryosphere undergoing accelerated regional climate change.

There are several hemispheric-scale satellite-derived snow-cover maps available, but none has been fully validated. For the period 23 October–25 December 2000, we compare snow maps of North America derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and operational snow maps from the U.S. National Oceanic and Atmospheric Administration (NOAA) National Operational Hydrologic Remote Sensing Center (NOHRSC), both of which rely on satellite data from the visible and near-infrared parts of the spectrum; we also compare MODIS maps with Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) passive-microwave snow maps for the same period. The maps derived from visible and near-infrared data are more accurate for mapping snow cover than are the passive-microwave-derived maps, but discrepancies exist as to the location and extent of the snow cover even between operational snow maps. The MODIS snow-cover maps show more snow in each of the 8 day periods than do the NOHRSC maps, in part because MODIS maps the effects of fleeting snowstorms due to its frequent coverage. The large (~30 km) footprint of the SSM/I pixel, and the difficulty in distinguishing wet and shallow snow from wet or snow-free ground, reveal differences up to 5.33 x 106 km2 in the amount of snow mapped using MODIS vs SSM/I data. Algorithms that utilize both visible and passive-microwave data, which would take advantage of the all-weather mapping capability of the passive-microwave data, will be refined following the launch of the Advanced Microwave Scanning Radiometer (AMSR) in the fall of 2001.

A pulse is a type of unstable glacier flow intermediate between normal flow and surging. Using Landsat MSS, TM and ETM+ imagery and feature-tracking software, a time series of mostly annual velocity maps from 1973 to 2012 was produced that reveals five pulses of Ruth Glacier, Alaska. Peaks in ice velocity were found in 1981, 1989, 1997, 2003 and 2010, approximately every 7 years. During these peak years the ice velocity increased 300%, from approximately 40 m a–1 to 160 m a–1. Based on the spatio-temporal behavior of Ruth Glacier during the pulse cycles, we suggest the pulses are due to enhanced basal motion via deformation of a subglacial till. The cyclical nature of the pulses is interpreted to be due to a thin till, with low permeability, that causes incomplete drainage of the till between the pulses, followed by eventual recharge and dilation of the till. These findings suggest care is needed when attempting to correlate changes in regional climate with decadal-scale changes in velocity, because in some instances basal conditions may have a greater influence on ice dynamics than climate.

The evolution of four dynamic radar glacier zones at the surface of an alpine icefield in British Columbia is monitored using a time series of 35 First European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) images acquired from 1992 to 1994. These zones result from changing wetness and textural properties, and appear to represent: (1) cold snow with no liquid water present; (2) an initial melt front with an upper boundary near the elevation of the 0° isotherm; (3) metamorphosed, rapidly melting first-year snow with a rough or pitted surface; and (4) bare ice. This interpretation is aided by temperature and runoff data, air photographs and field measurements of snowpack properties acquired with two ERS-1 SAR scenes, ice-surface elevations derived from 1:50 000 topographic maps and simulations of radar backscatter from a geometric optics model of surface scattering. Meltwater production is affected by the development of zones (2), (3) and (4), which form, migrate up-elevation and disappear each year between April and September.

Vatnajökull, Iceland, is the Earth’s most studied ice cap and represents a classical glaciological field site on the basis of S. Pálsson’s seminal glaciological field research in the late 18th century. Since the 19th century, Vatnajökull has been the focus of an array of glaciological studies by scientists from many nations, including many remote-sensing investigations since 1951. Landsat-derived positions of the termini of 11 outlet glaciers of Vatnajökull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973–92. The largest changes during the 19 year period (1973–92) occurred in the large lobate, surge-type outlet glaciers along the southwestern, western, and northern margins of Vatnajökull. Tungnaárjökull receded −1413 ± 112 m (−1380 ± 1 m from ground observations), and Brúarjökull receded −1975 ± 191 m (−2096 ± 5 m from extrapolated ground observations) between 1973 and 1992. Satellite images can be used to delineate glacier margin changes on a time-lapse basis, if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance/recession is larger than maximum image pixel size. “Local knowledge” of glaciers is critically important, however, in the accurate delineation of glacier margins on Landsat images.

Objectives: The aim of this study was to determine the timing of neonatal cardiac intervention in babies with antenatally diagnosed congenital heart disease and the impact on obstetric management. Methods: A retrospective review of all deliveries between January, 2008 and December, 2009 was conducted in a tertiary centre with foetal and paediatric cardiology, maternal–foetal medicine, and obstetric units. All live births with antenatally detected congenital heart disease were included. Data were collected from foetal, paediatric cardiology, and maternity databases and records. Induction, delivery mode, and timing of the first cardiac intervention in the neonate were studied. Results: 205 deliveries were included. Induction and elective Caesarean section rates were 51.2% (105/205) and 14.1% (29/205), respectively. The vaginal delivery rate was 56% (115/205). There was a non-significant trend towards a higher rate of vaginal delivery after spontaneous labour than after induction (75% versus 66%; p = 0.234). The rate of neonatal cardiac intervention during the initial stay was 59.5% (122/205); it was 18.5% (38/205) within 48 hours and 25.8% (53/205) within 72 hours. The median time to first intervention was 4 days (interquartile range 2–8). Babies with hypoplastic left heart syndrome (median 3, interquartile range 2–6), transposition of the great arteries (median 1, interquartile range 0–4.5), and arrhythmia (median 0.5, interquartile range 0–1) had a significantly earlier time to first intervention compared with those with other conditions (p = 0.001). Conclusion: Vaginal delivery can be achieved in women delivering babies with major congenital heart disease at a tertiary centre. Delivery in or near a tertiary centre is recommended for patients requiring early intervention, of which many can be identified in advance.

Interest group spending on issue advertising is growing dramatically, but we know very little about its deployment and purpose in legislative advocacy. This article begins to fill the gap, examining where, when, and why interest groups run television issue advertisements. We start from the premise that issue advertising is a form of outside lobbying, but we argue that it can serve two legislative ends. We hypothesize, first, that group strategists will target areas represented by committee allies they want to mobilize more than pivotal members they want to convert. When a roll call is approaching and the vote is likely to be close, however, groups will expand their advertising targets to include floor voters near the chamber pivot. Our statistical tests use data on television issue ads concerning the 2003 Medicare prescription drug bill. The analysis provides consistent support for the first hypothesis and mixed support for the second.