Band narrowing and Mott localization in iron oxychalcogenides La2O2Fe2O(Se,S)2

Bad metal properties have motivated a description of the parent iron pnictides as correlated metals on the verge of Mott localization. What has been unclear is whether interactions can push these and related compounds to the Mott-insulating side of the phase diagram. Here we consider the iron oxychalcogenides La2O2Fe2O(Se,S)2, which contain an Fe square lattice with an expanded unit cell. We show theoretically that they contain enhanced correlation effects through band narrowing compared to LaOFeAs, and we provide experimental evidence that they are Mott insulators with moderate charge gaps. We also discuss the magnetic properties in terms of a Heisenberg model with frustrating J1-J2-J2' exchange interactions on a "doubled" checkerboard lattice.

Applying graphics processor units to Monte Carlo dose calculation in radiation therapy

We investigate the potential in using of using a graphics processor unit (GPU) for Monte-Carlo (MC)-based radiation dose calculations. The percent depth dose (PDD) of photons in a medium with known absorption and scattering coefficients is computed using a MC simulation running on both a standard CPU and a GPU. We demonstrate that the GPU's capability for massive parallel processing provides a significant acceleration in the MC calculation, and offers a significant advantage for distributed stochastic simulations on a single computer. Harnessing this potential of GPUs will help in the early adoption of MC for routine planning in a clinical environment.

Medical engineering at Cardiff University. Part 2: Postgraduate programmes of study

The Medical Engineering team within the School of Engineering, Cardiff University, delivers two postgraduate programmes of study. Established over 10 years ago, the part-time MSc programmes in Orthopaedic Engineering and Clinical Engineering offer the opportunity of further study while remaining within full-time employment. Both programmes deliver 120 taught credits over two academic years via a series of residential weekends, with successful completion enabling the student to undertake and then defend a 60-credit research dissertation. Fulfilling a specific role on the career pathway for both student cohorts, the strength of each programme is indicated by the consistent number of applicants.

Medical engineering at Cardiff University. Part 1: Undergraduate programmes of study

Cardiff University has offered a medical engineering undergraduate programme since 2001 and hence delivers one of the longest-running and most established medical engineering programmes within the UK. It currently offers BEng (Hons) and MEng (Hons) programmes that are both accredited by the Institution of Mechanical Engineers and include the option to undertake a year in industrial employment. The admissions policy ensures that the intake consists of a diverse range of students and is typically very successful in attracting female students. The programmes consist of six key academic threads which ensure that the content is both relevant and continuous, with all threads tailored to provide a patient-focused learning environment. Students initially learn core and fundamental principles in years 1 and 2, supported by a range of laboratories and practical experimentation. The latter years then encourage the students to corroborate and apply this knowledge, including involvement in a range of project-based learning exercises. The programme is delivered by a core of experienced academic medical engineers, with support from other engineering colleagues, as well as colleagues from the School of Biosciences, the School of Medicine, and the National Health Service. Thus, the programme delivers a wide range of modules which guarantee that graduating students have a thorough understanding of all possible career options. These two factors are significant in making it possible for students to follow their chosen career path upon graduation.

Characterisation and aerosolisation of mannitol particles produced via confined liquid impinging jets

Mannitol particles, produced by spray drying (SD), have been used commercially (Aridol) in bronchial provocation test. In this study, we propose an alternative method to produce inhalable mannitol powders. The elongated mannitol particles (number median length 4.0microm, and axial ratio of 3.5) were prepared using a confined liquid impinging jets (CLIJs) followed by jet milling (JM). Spray dried and jet milled raw mannitol particles were compared in an attempt to assess the performance of the particles produced by the new method. Aerosol performance of the three different powders (CLIJ, SD, and JM) was relatively poor (fine particle fraction or FPF(loaded) below 15%) when dispersed by the Rotahaler. Dispersion through the Aeroliser led to better aerosol performance of the CLIJ mannitol (FPF(loaded) 20.3%), which is worse than the JM (FPF(loaded) 30.3%) and SD mannitol particles (FPF(loaded) 45.7%) at 60 L/min, but comparable (FPF(loaded) 40.0%) with those of the JM (FPF(loaded) 40.7%) and SD (FPF(loaded) 45.5%) powders at 100L/min. Hence, the optimum use of these elongated mannitol particles can be achieved at increased air flow with a more efficient inhaler. In addition to crystallinity, morphology, and particle size distribution, the surface energies of these powders were measured to explain the differences in aerosol performance. A major advantage of using the CLIJ method is that it can be scaled up with a good yield as the precipitate can be largely collected and recovered on a filter, compared with spray drying which has a low collection efficiency for fine particles below 2microm.

Rib fractures in infancy: establishing the mechanisms of cause from the injuries--a literature review

In the absence of a history of a significant accidental event, the most likely diagnosis in an infant with rib fractures is non-accidental injury. Medical opinion is essential when deciding if child abuse has taken place or not and this requires a consideration of whether a proposed causal explanation fits with the observed injuries. To assist in the interpretation of injuries and inform medical practitioners, it is essential to develop a clear understanding of their biomechanical mechanism of causation. The types and 'likely' mechanisms of rib fracture are well-documented, however, what forces, deflections and loading rates are required to produce particular fractures are relatively unknown. This paper presents a review of the literature, from a biomechanical engineering perspective, to assess information regarding the various types of rib fracture and their likely mechanisms, paying particular attention to the likely forces, deflections and loading rates involved. The biomechanical parameters, applied during 'two finger' infant cardiopulmonary resuscitation (CPR), are identified and discussed, and are currently believed to be below the limit at which rib fracture may occur. However, a new 'two thumb' CPR technique is identified which involves a holding/gripping mechanism of the infant thorax, similar to that which is believed to occur in inflicted injury scenarios, such as shaking. The two thumb method may provide a greater magnitude of force and deflection, a greater rate of loading and may perhaps pose a greater risk of fracture, compared with the 'two finger' supine, anterior-posterior chest compression approach. It is proposed to introduce a force/deflection boundary condition into mechanical and computer/numeric infant models. Subject to the future inclusion of loading rate/response data, a three-dimensional (force/deflection/loading rate) boundary condition will be used to provide a minimum injury threshold for potentially injurious scenarios. A number of further studies are suggested, since this paper is intended to provide a first step to developing a more sophisticated understanding of the causes of infant rib fracture. Areas of further study include specific rib fracture mechanisms, as well as the effects of age dependent characteristics, positioning and area of force application. Such additional information would allow the proposed initial boundary condition to be further refined to provide an indication of the likelihood, type and number of fractures that might be expected.

A fatal fall from a balcony? A biomechanical approach to resolving conflicting witness accounts

An adult male was found below a third floor balcony having sustained fatal head injuries. An account provided by a witness described how the deceased had been in high spirits and had engaged in swinging from the third floor balcony rail in an attempt to swing onto a lower second floor balcony and whilst doing so had lost his grip and fallen (10.67 metres) to the ground below. A conflicting account was provided, some weeks later, by a second witness, who claimed to have observed an argument between two men on a third floor balcony, during which one had vigorously pushed the other over the balcony rail. The push, it was alleged, caused the man to move very quickly over the balcony rail and fall in an 'upturned crucifix' position to the ground. This paper describes a series of biomechanical experiments, conducted on a reconstruction of the third floor balcony and the second floor balcony rail, during which a volunteer was subjected to the two fall scenarios, in an attempt to resolve the conflicting witness accounts. Analysis of human movement was performed using a 3-D motion analysis system, markers were placed at the volunteer's key joint centres and were tracked to determine physical parameters. The parameter values were used to calculate what dynamic movements may have occurred had the volunteer been allowed to fall, not just a distance equivalent to the lower balcony rail but a greater distance, equivalent to that between the balcony and the ground. Calculations indicate that during the hanging-fall scenario a range of body rotation was produced between 159 degrees and 249 degrees, that is, an upturned head-first body orientation, consistent with that required to produce the described injuries and consistent with the description provided by the first witness. The push-fall scenario, however, produced a greater estimated body rotation of between 329 degrees and 530 degrees, equal to the body rotating, from the point of free-fall to the moment of impact, between almost 1 and 1.5 times. This was consistent with the described injuries but inconsistent with the description provided by the second witness. It was therefore concluded that although both the accidental and inflicted-push scenarios could produce a body orientation consistent with the reported injuries, only the accidental scenario produced a fall which could be described as an 'upturned crucifix', since the push scenario produced a significantly greater body rotation. The witness who alleged that the deceased had been pushed later retracted his statement.

Development of a simulation system for performing in situ surface tests to assess the potential severity of head impacts from alleged childhood short falls

There is considerable debate in the medical literature surrounding the issue of fatal child head injuries being caused by short falls. When reviewing a case history a medical expert will form an opinion of the likely cause of an injury based on his/her knowledge of the literature, training and experience of similar cases. The severity of an injury is determined by the age of the victim, fall height, body impact site and the impact surface. A medical expert, when forming an opinion, is invariably assisted by a description of the scene or scene photographs and assumes the mechanical response of the floor conforms in the same way to "similar" surfaces. The impact response characteristics of the entire surface mixture is critically important when considering the potential for head injury to a child due to a short fall. However, at present during an investigation, the response of a surface to a head impact remains an unknown, since a simple description of, or cursory glance at, a floor surface is insufficient in determining its potential to cause injury. This paper documents the development of a simulation system for assessing the impact response, and potential to cause injury, of domestic floor surfaces during short falls. The method utilises a headform and drop tower adapted from techniques and current standards used to assess the potential for childhood head injuries of playground surfaces and pedestrian-bonnet impacts. The results suggest that the potential of a surface to cause head injury is dependent on the entire surface mixture, including the top surface layer (e.g. carpet and underlay), the underlying surface (wood, chipboard or concrete) and the support material (joists, supports. etc.). The results illustrate a wide range of injury potential between surface mixtures. The simulation system shows the potential to discriminate between differences in surface mixture. In conclusion, the authors suggest that in future investigations, the response of the entire surface mixture be taken into account when forming an opinion on the injury potential of short falls.

Soil factors controlling mineral N uptake by Picea engelmannii seedlings: the importance of gross NH4+ production rates

* Hydroponic studies suggest that plant nitrogen (N) demand determines the rate of mineral N uptake; however, field observations show N limitation to be widespread. Field experiments are needed to understand soil factors controlling mineral N uptake. * We planted Picea engelmannii seedlings that had initially been grown from sterilized seeds, on a recently clearcut site. We applied a hybrid isotope dilution/pulse labelling technique to compare the gross production rate, concomitantly to the plant uptake rate, of soil mineral N. We also measured mineral N concentrations, microbial N, and percent ectomycorrhizal root tips. * Gross NH4+ production rate was the most important determinant of plant uptake rate. Exploratory path analysis suggested that plant uptake was also determined by microbial N, which was, in turn, determined by soil mineral N concentrations. Percent ectomycorrhizal root tips was negatively related to gross NO3- production rate and microbial N concentrations. * We conclude that nutrient flux density is important in controlling plant uptake. Mycorrhizal colonization may alter N dynamics in the rhizosphere without affecting mineral N uptake by seedlings.

New pseudophase structure for alpha-Pu

We propose a new pseudophase crystal structure, based on an orthorhombic distortion of the diamond structure, for the ground-state alpha phase of plutonium. Electronic-structure calculations in the generalized-gradient approximation give approximately the same total energy for the two structures. Interestingly, our new pseudophase structure is the same as the gamma-Pu structure except with very different b/a and c/a ratios. We show how the contraction relative to the gamma phase, principally in the z direction, leads to an alpha-like structure in the [0,1,1] plane and reproduces the short range bonds of the alpha phase. This is an important link between two complex structures of Pu and opens new possibilities for exploring the very rich phase diagram of Pu through theoretical calculations.

Head injury and limb fracture in modern playgrounds

There were no serious head injuries in modern Cardiff municipal playgrounds with safety surfaces over five years injury surveillance. The literature suggests serious head injuries did occur before the introduction of safety surfaces.

New mechanism for the alpha to omega martensitic transformation in pure titanium

We propose a new direct mechanism for the pressure driven alpha-->omega martensitic transformation in pure titanium. A systematic algorithm enumerates all possible pathways whose energy barriers are evaluated. A new, homogeneous pathway emerges with a barrier at least 4 times lower than other pathways. The pathway is shown to be favorable in any nucleation model.

Genetic diversity: frameshift mechanisms alter coding of a gene (Epstein-Barr virus LF3 gene) that contains multiple 102-base-pair direct sequence repeats

Frameshift mutations provide recognized mechanisms for changing the coding potential of an organism. Here, multiple frameshifts are identified in repetitive sequences within an Epstein-Barr virus unspliced early gene, LF3, which is associated with the viral replicative cycle and also transcriptionally expressed in many virally associated tumors. On the DNA strand encoding LF3, there are three open reading frames, only one of which contains an initiation codon. Most (>95%) of the gene consists of numerous (>20, varying with cell source) GC-rich copies of a 102-bp direct repeat (called IR 4) flanked by small unique sequences. LF3 may express a protein if its initiation and termination codons reside in the same reading frame, but this is not always the case. Frameshifting events, occurring in short runs of pyrimidines (mainly C residues) in the repeats, give rise to mutations which may provide a mechanism for escape of an LF3 function from host surveillance. Sequence studies link these frameshifts to DNA replication errors. Notably, the number of sites in LF3 at which such mutations can occur permits a very large amount of diversity in this gene. Our data also suggest a second degeneracy mechanism within the protein itself, which influences its stability and may reflect a host defense mechanism. LF3 thus provides a potentially important model for studying the quest for supremacy between a virus and its host.

Subdural haemorrhage sustained in a baby-rocker? A biomechanical approach to causation

An unconscious 8 weeks old infant was admitted to hospital and found to have bilateral, subdural and retinal haemorrhages. He died the following day. The explanation for the subdural haemorrhage put forward by his carers was that the infant had been in a baby-rocker and that the carers had seen the rocker being rocked vigorously by their 14 months old daughter on two separate occasions. This paper describes the biomechanics of an infant model in the particular baby-rocker used and determines the maximum forces generated, comparing them with the 'forces' thought to be compatible with the causation of subdural haemorrhage.

The potential and limitations of utilising head impact injury models to assess the likelihood of significant head injury in infants after a fall

The use of engineering principles in assessing head injury scenarios is of increasing significance in investigations into suspected child abuse. A fall scenario is often given as the history for a head injury to an infant. This paper addresses the basic engineering principles and factors to be considered when calculating the severity of a head impact after free-fall. The application of head injury models (HIMs) to ascertain the forces involved in childhood head injuries from impact is also discussed. Previous studies including Duhaime et al. [J. Neurosurg. 66 (1987) 409] and Nokes et al. [Forensic Sci. Int. 79 (1995) 85] have utilised HIMs for this purpose: this paper reviews those models most widely documented.The HIM currently considered the 'state-of-the-art' is the head injury criterion (HIC) and it is suggested that this model should be utilised for assessing head impact injury in child abuse cases where appropriate.

Expression of catecholaminergic mRNAs in the hyperactive mouse mutant coloboma

The SNAP-25 deficient mouse mutant coloboma (Cm/+) is an animal model for investigating the biochemical basis of locomotor hyperactivity. The spontaneous hyperactivity exhibited by coloboma is three times greater than control mice and is a direct result of the SNAP-25 deletion. SNAP-25 is a presynaptic protein that regulates exocytotic neurotransmitter release; coloboma mice express only 50% of normal protein concentrations. Previous research has determined that there is an increase in the concentration of norepinephrine but a decrease in dopamine utilization in the striatum and nucleus accumbens of coloboma mice. In situ hybridization analysis revealed that there were corresponding increases in tyrosine hydroxylase (TH) mRNA expression in noradrenergic cell bodies of the locus coeruleus of Cm/+ mice. In contrast, TH mRNA expression in substantia nigra appeared normal in the mutant mouse. alpha(2)-Adrenergic receptors are important modulators of central noradrenergic function and dopamine release. In situ hybridization data revealed that alpha(2A)-adrenergic receptor mRNA expression is upregulated in Cm/+ mice. These results suggest an underlying abnormality in noradrenergic regulation in this hyperactive mouse mutant.

A novel approach to forensic investigation: three-dimensional kinematic and kinetic motion analysis

Following a domestic incident, a five-year-old child was pronounced dead on arrival at hospital. The subsequent post-mortem examination found that the cause of death was peritonitis as a result of a rupture of the duodenum. During the police interview, the main suspect alleged that the injury occurred whilst playing a game which involved standing on the child's abdomen and chest. A reconstruction of the game was performed using 3-dimensional kinematic and kinetic motion analysis to investigate the feasibility of the statement as described by the defendant. Presented is a summary of the investigation together with a description of kinematic and kinetic methods employed.

A biomechanical reconstruction of a wound caused by a glass shard--a case report

During the course of a criminal trial, an investigating pathologist is commonly asked how much force was required to produce an injury. This subjective opinion is based on the pathologist's previous experience of dealing with wounds inflicted with similar weapons. However, in the case of stab wounds inflicted by broken glass, it is unlikely that two glass fragments would be physically similar. In the case studied, two theories were examined: that a wound resulted from a thrown glass fragment or that it had been caused as a stab injury by the glass held in the bare hand. The investigation involved quantifying the energy required for human tissue penetration, comparison of sharpness, a biomechanical analysis of throwing actions and testing of the hypothesis that if the glass shard were used as a stabbing implement it would result in a cut to the hand.The investigation utilised a scientific methodology that reduced the need for speculative (though informed) opinion from the pathologist by producing quantitative results.

Abnormal presynaptic catecholamine regulation in a hyperactive SNAP-25-deficient mouse mutant

The consequences of a reduction in the presynaptic protein, SNAP-25, were investigated to determine the neurochemical basis of the marked hyperlocomotor activity in coloboma (Cm/+) mice. SNAP-25 is part of the minimal presynaptic machinery necessary for exocytotic neurotransmitter release. Reserpine treatment was used to deplete vesicular stores of catecholamines. Coloboma mice were more sensitive to the effects of reserpine than control mice. However, presynaptic regulation of dopamine (DA) release, as assessed by low-dose apomorphine challenge, was intact. There were region-specific reductions in in vivo tyrosine hydroxylation and the DA metabolites homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum and nucleus accumbens of Cm/+ mice. While hyperactivity is often associated with changes in DA concentration, norepinephrine (NE) concentration was significantly increased in the striatum and nucleus accumbens of the hyperactive mutant. The increase in NE may regulate the hyperactivity in these mice, as suggested by current hypotheses of the mechanisms underlying attention-deficit hyperactivity disorder (ADHD) and Tourette's syndrome.

Identification of incompletely processed potential carboxypeptidase E substrates from CpEfat/CpEfat mice

In an attempt to identify peptides that may be involved in the obese phenotype observed in CpEfat/CpEfat mice (deficient in Carboxypeptidase E, CpE) samples from fourteen neuroendocrine tissues in wild-type and CpEfat/CpEfat mice were obtained. Peptides were purified from these tissues and potential CpE substrate peptides were enriched using an anhydrotrypsin column that captures peptides with basic C-termini. Bound peptides were subjected to tryptic digestion and followed by liquid chromatography-mass spectrometry analysis. The relative levels of CpEfat/CpEfat versus wild-type peptides were determined by comparison of the ion intensities. Peptide ions elevated in the CpEfat/CpEfat samples were identified by targeted liquid chromatography-tandem mass spectrometry. From those ions, 27 peptides derived from known neuropeptides (including CpE substrates) were identified, together with another 25 peptides from proteins not known to be components of the neuropeptide processing pathway. The known CpE substrates identified included the recently discovered proSAAS, granin-like neuroendocrine peptide precursor that inhibits prohormone processing. The approach demonstrated the feasibility of using an affinity-based method for identifying differences in specific classes of peptides between normal and mutant mice.

Final report of the FOPE II Financing of Pediatric Education Workgroup

Some of the challenges of financing pediatric medical education are shared with all medical education; others are specific to pediatrics. The general disadvantage that funding of graduate medical education (GME) is linked to reimbursement for clinical care has uniquely negative consequences for freestanding children's hospitals because they therefore receive little Medicare GME support. This represents both a competitive disadvantage for such hospitals and an aggregate federal underinvestment in children's health care that now amounts to billions of dollars. The need to subsidize medical student and subspecialty education with clinical practice revenue jeopardizes both activities in pediatric departments already burdened by inadequate reimbursement for children's health care and the extra costs of ambulatory care. The challenges of funding are complicated by rising costs as curriculum expands and clinical education moves to ambulatory settings. Controversies over prioritization of resources are inevitable. Solutions require specification of costs of education and a durable mechanism for building consensus within the pediatric community. Pediatrics 2000;106(suppl):1256-1269; medical student education, continuing medical education, medical subspecialties, children, pediatrics, health maintenance organizations, managed care, hospital finances, children's hospitals.