Searching for intra-cloud positive leaders in VHF.

We have used the LOw-Frequency ARray (LOFAR) to search for the growing tip of an intra-cloud (IC) positive leader. Even with our most sensitive beamforming method, where we coherently add the signals of about 170 antenna pairs, we were not able to detect any emission from the tip. Instead, we put constraints on the emissivity of very-high frequency (VHF) radiation from the tip at 0.5 pJ/MHz at 60 MHz, integrated over 100 ns. The limit is independent on whether this emission is in the form of short pulses or continuously radiating. The non-observation of VHF radiation from intra-cloud positive leaders implies that they proceed in an extremely gradual process, which is in sharp contrast with the observations of other parts of a lightning discharge.

The Relationship of Lightning Radio Pulse Amplitudes and Source Altitudes as Observed by LOFAR.

When a lightning flash is propagating in the atmosphere it is known that especially the negative leaders emit a large number of very high frequency (VHF) radio pulses. It is thought that this is due to streamer activity at the tip of the growing negative leader. In this work, we have investigated the dependence of the strength of this VHF emission on the altitude of such emission for two lightning flashes as observed by the Low Frequency ARray (LOFAR) radio telescope. We find for these two flashes that the extracted amplitude distributions are consistent with a power-law, and that the amplitude of the radio emissions decreases very strongly with source altitude, by more than a factor of 2 from 1 km altitude up to 5 km altitude. In addition, we do not find any dependence on the extracted power-law with altitude, and that the extracted power-law slope has an average around 3, for both flashes.

A distinct negative leader propagation mode.

The common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km[Formula: see text]) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket.

Determining Electric Fields in Thunderclouds With the Radiotelescope LOFAR.

An analysis is presented of electric fields in thunderclouds using a recently proposed method based on measuring radio emission from extensive air shower events during thunderstorm conditions. This method can be regarded as a tomography of thunderclouds using cosmic rays as probes. The data cover the period from December 2011 till August 2014. We have developed an improved fitting procedure to be able to analyze the data. Our measurements show evidence for the main negative-charge layer near the -10° isotherm. This we have seen for a winter as well as for a summer cloud where multiple events pass through the same cloud and also the vertical component of the electric field could be reconstructed. On the day of measurement of some cosmic-ray events showing evidence for strong fields, no lightning activity was detected within 100 km distance. For the winter events, the top heights were between 5 and 6 km, while in the summer, typical top heights of 9 km were seen. Large horizontal components in excess of 70 kV/m of the electric fields are observed in the middle and top layers.

Radio Emission Reveals Inner Meter-Scale Structure of Negative Lightning Leader Steps.

We use the Low Frequency Array (LOFAR) to probe the dynamics of the stepping process of negatively charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of vhf (30-80 MHz) radiation are emitted in short-duration bursts (<10 µs). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain x-ray emission from lightning leaders, as x rays from laboratory leaders tend to be associated with corona flashes. Surprisingly, we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models.

Needle-like structures discovered on positively charged lightning branches.

Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends-called positive and negative leaders1. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30-300-megahertz frequency band2-8 that can be remotely sensed and imaged with high spatial and temporal resolution9-11. Positive leaders propagate more continuously and thus emit very little high-frequency radiation12. Radio emission from positive leaders has nevertheless been mapped13-15, and exhibits a pattern that is different from that of negative leaders11-13,16,17. Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders9,12,16,18-20, which may lead to current pulses that both reconnect positive leaders to negative leaders11,16,17,20-22 and cause multiple cloud-to-ground lightning events1. The disconnection process is thought to be due to negative differential resistance18, but this does not explain why the disconnections form primarily on positive leaders22, or why the current in cloud-to-ground lightning never goes to zero23. Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures-which we call 'needles'-that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.

LOFAR Lightning Imaging: Mapping Lightning With Nanosecond Precision.

Lightning mapping technology has proven instrumental in understanding lightning. In this work we present a pipeline that can use lightning observed by the LOw-Frequency ARray (LOFAR) radio telescope to construct a 3-D map of the flash. We show that LOFAR has unparalleled precision, on the order of meters, even for lightning flashes that are over 20 km outside the area enclosed by LOFAR antennas (∼3,200 km2), and can potentially locate over 10,000 sources per lightning flash. We also show that LOFAR is the first lightning mapping system that is sensitive to the spatial structure of the electrical current during individual lightning leader steps.

Health spending, illicit financial flows and tax incentives in Malawi.

This analysis examines the gaps in health care financing in Malawi and how foregone taxes could fill these gaps. It begins with an assessment of the disease burden and government health expenditure. Then it analyses the tax revenues foregone by the government of Malawi by two main routes: Illicit financial flows (IFF) from the country, Tax incentives. We find that there are significant financing gaps in the health sector; for example, government expenditure is United States Dollars (USD) 177 million for 2013/2014 while projected donor contribution in 2013/2014 is USD 207 million and the total cost for the minimal health package is USD 535 million. Thus the funding gap between the government budget for health and the required spending to provide the minimal package for 2013/2014 is USD 358 million. On the other hand we estimate that almost USD 400 million is lost through IFF and corporate utilization of tax incentives each year. The revenues foregone plus the current government health spending would be sufficient to cover the minimal public health package for all Malawians and would help tackle Malawi's disease burden. Every effort must be made, including improving transparency and revising laws, to curtail IFF and moderate tax incentives.

Economics and ethics of paediatric respiratory extra corporeal life support.

Extra corporeal membrane oxygenation (ECMO) is a form of life support, which facilitates gas exchange outside the body via an oxygenator and a centrifugal pumping system. A paediatric cardiac ECMO programme was established in 2005 at Our Lady's Children's Hospital, Crumlin (OLCHC) and to date 75 patients have received ECMO, the majority being post operative cardiac patients. The outcome data compares favourably with international figures. ECMO has been most successful in the treatment of newborn infants with life threatening respiratory failure from conditions such as meconium aspiration, respiratory distress syndrome and respiratory infections. There is no formal paediatric respiratory ECMO programme at OLCHC, or anywhere else in Ireland. Currently, neonates requiring respiratory ECMO are transferred to centres in Sweden or the UK at an average cost of 133,000 Euros/infant, funded by the Health Service Executive E112 treatment abroad scheme. There is considerable morbidity associated with the transfer of critically ill infants, as well as significant psycho-social impact on families. OLCHC is not funded to provide respiratory ECMO, although the equipment and expertise required are similar to cardiac ECMO and are currently in place. The average cost of an ECMO run at OLCHC is 65,000 Euros. There is now a strong argument for a fully funded single national cardiac and respiratory paediatric ECMO centre, similar to that for adult patients.

View Point: Economic Growth and Child Health in Sub Saharan Africa

After independence most African countries witnessed growth in their economies and decreases in child mortality. However both economic growth and the gains in under 5 mortality slowed dramatically in the 1980s and 1990s

Epidemiology of major paediatric trauma.

In Europe injury is the leading cause of death in those aged between 1 and 14 years. In Ireland over 800,000 people are aged less than 14 years. There is currently no national trauma register to collect data on the morbidity and mortality associated with major trauma in the paediatric population in Ireland. We prospectively collected data on 153 patients admitted to our hospital with major trauma. There were 99 males and 54 females. The majority of patients were transported by ambulance (n= 138). Road traffic accidents (n=69) and thermal injuries (n=49) represented the majority of admissions. 68% (n=47) of the vehicle occupants in this study were either unrestrained or incorrectly restrained. Most patients (n=133) had an in patient stay of <50 days, with only 4 patients staying >100 days. 14 patients died. A paediatric trauma register as well as a level 1 paediatric trauma centre are required in Ireland.

The relationship between vascular expansion of the aorta and pulmonary artery and the genesis of the impedance cardiogram using the technique of sonomicrometry.

PRIMARY OBJECTIVE: This prospective animal study aims to evaluate the contribution of the pulmonary artery (PA) and aorta on the morphology of the impedance cardiogram using sonomicrometry. METHODS: Impedance electrodes were placed around the thorax, aorta and in the oesophagus of five dogs. Sonomicrometry crystals were mounted on the PA and aorta for tracking vascular distension while a Doppler flow probe measured aortic blood flow. RESULTS: No significant differences (p > 0.05) were recorded between the onset of aortic expansion, aortic blood flow and the start of the impedance dZ/dt signal. Significant differences (p > 0.001) were recorded between the onset of PA expansion and the dZ/dt signal. PA expansion began 41.6 +/- 6.0 ms, 60.7 +/- 7.2 ms and 42.2 +/- 4.9 ms respectively, before surface, aortic and oesophageal impedance recordings. CONCLUSION: The genesis of the impedance cardiogram is attributed to volumetric expansion of the aorta.

A pilot study to determine if nurses trained in basic neonatal resuscitation would impact the outcome of neonates delivered in Kampala, Uganda.

AIMS AND OBJECTIVES: To determine if a team dedicated to basic neonatal resuscitation in the delivery ward of a teaching hospital would impact the outcome of neonates delivered in Kampala, Uganda. METHODS: A five-member team of nurses, trained in basic neonatal resuscitation attended 1046 deliveries over a thirty-one day pilot period. They were available in the delivery ward twenty-four hours each day. Outcomes studied included the number of stillbirths recorded on the delivery ward, the number of neonates admitted to the special care baby unit (SCBU), the number of babies admitted to SCBU who died and the mortality in the different weight categories. APGAR scores before and after intervention was also compared. Admission diagnoses between the two groups were also compared. Outcome data collected during this pilot period was compared with historic controls from the previous 31 days in the same unit. PATIENTS AND SETTING: A delivery ward, 22,000 deliveries per year. RESULTS: The stillbirth rate and admission rate to the SCBU were unchanged. Basic neonatal resuscitation in this setting decreased the incidence of asphyxia (defined as failure to initiate and sustain breathing or an APGAR score of <7 at 5 min), improved APGARS and a decrease in the mortality of babies weighing more than 2 kg. CONCLUSION: The resuscitation team reduced the incidence of and mortality from asphyxia and improved the outcome of babies greater than 2 kg. This pilot study provides evidence of the beneficial effect of basic neonatal resuscitation in this setting.

Home-based care for orphaned children infected with HIV/AIDS in Uganda.

The primary aim of this paper is to describe an outreach programme from a main state hospital in sub-Saharan Africa, which has been running for three years. This programme is based in Mulago Hospital, Kampala, Uganda and cares for up to 200 children infected with HIV/AIDS in their home. We describe the clinic and how we meet the families and enrol them, the infrastructure of the programme and the personnel involved. Children and their families receive physical, psychological and social care and we describe each aspect of this. The knowledge base about older children with AIDS in Africa is scarce and the secondary aim of this paper is to publish observations that were made while providing care. This includes demographics and the health problems encountered among children living with HIV/AIDS in a resource-poor setting who do not receive antiretroviral medication. Finally, we discuss the strengths and weaknesses of this model of care and the prerequisites to setting up a similar model.

Paediatric near-drowning: mortality and outcome in a temperate climate.

The decision whether to continue to resuscitate the paediatric victim of near-drowning is influenced by potential poor neurological outcome. A low core body temperature at presentation is frequently cited as a reason to continue resuscitation. We report the case of an 11 month old infant admitted to the intensive care unit following near-drowning and a prolonged resuscitation. The infant's core body temperature was 29 degrees C. Cardiac output was restored, but the child remains in a persistent vegetative state. We present the results of a ten year review of near-drowning in a tertiary referral institution, to evaluate the mortality and outcome in a temperate climate. Thirteen patients were identified in the review. The mortality was 23%. The incidence of a persistent vegetative state was 15%. Asystole, immersion time greater than 15 minutes, resuscitation time longer than 30 minutes, the administration of epinephrine, and a low core body temperature were associated with a poor outcome.