3-D Ultrastructure of O. tauri: Electron Cryotomography of an Entire Eukaryotic Cell

The hallmark of eukaryotic cells is their segregation of key biological functions into discrete, membrane-bound organelles. Creating accurate models of their ultrastructural complexity has been difficult in part because of the limited resolution of light microscopy and the artifact-prone nature of conventional electron microscopy. Here we explored the potential of the emerging technology electron cryotomography to produce three-dimensional images of an entire eukaryotic cell in a near-native state. Ostreococcus tauri was chosen as the specimen because as a unicellular picoplankton with just one copy of each organelle, it is the smallest known eukaryote and was therefore likely to yield the highest resolution images. Whole cells were imaged at various stages of the cell cycle, yielding 3-D reconstructions of complete chloroplasts, mitochondria, endoplasmic reticula, Golgi bodies, peroxisomes, microtubules, and putative ribosome distributions in-situ. Surprisingly, the nucleus was seen to open long before mitosis, and while one microtubule (or two in some predivisional cells) was consistently present, no mitotic spindle was ever observed, prompting speculation that a single microtubule might be sufficient to segregate multiple chromosomes

A formally verified compiler back-end

This article describes the development and formal verification (proof of semantic preservation) of a compiler back-end from Cminor (a simple imperative intermediate language) to PowerPC assembly code, using the Coq proof assistant both for programming the compiler and for proving its correctness. Such a verified compiler is useful in the context of formal methods applied to the certification of critical software: the verification of the compiler guarantees that the safety properties proved on the source code hold for the executable compiled code as well

Detection of the pairwise kinematic Sunyaev-Zel'dovich effect with BOSS DR11 and the Atacama Cosmology Telescope

We present a new measurement of the kinematic Sunyaev-Zeldovich effect using data from the Atacama Cosmology Telescope (ACT) and the Baryon Oscillation Spectroscopic Survey (BOSS). Using 600 square degrees of overlapping sky area, we evaluate the mean pairwise baryon momentum associated with the positions of 50,000 bright galaxies in the BOSS DR11 Large Scale Structure catalog. A non-zero signal arises from the large-scale motions of halos containing the sample galaxies. The data fits an analytical signal model well, with the optical depth to microwave photon scattering as a free parameter determining the overall signal amplitude. We estimate the covariance matrix of the mean pairwise momentum as a function of galaxy separation, using microwave sky simulations, jackknife evaluation, and bootstrap estimates. The most conservative simulation-based errors give signal-to-noise estimates between 3.6 and 4.1 for varying galaxy luminosity cuts. We discuss how the other error determinations can lead to higher signal-to-noise values, and consider the impact of several possible systematic errors. Estimates of the optical depth from the average thermal Sunyaev-Zeldovich signal at the sample galaxy positions are broadly consistent with those obtained from the mean pairwise momentum signal.Comment: 15 pages, 8 figures, 2 table

Cryo-EM structure of a helicase loading intermediate containing ORC-Cdc6-Cdt1-MCM2-7 bound to DNA

In eukaryotes, the Cdt1-bound replicative helicase core MCM2-7 is loaded onto DNA by the ORC-Cdc6 ATPase to form a prereplicative complex (pre-RC) with an MCM2-7 double hexamer encircling DNA. Using purified components in the presence of ATP-γS, we have captured in vitro an intermediate in pre-RC assembly that contains a complex between the ORC-Cdc6 and Cdt1-MCM2-7 heteroheptamers called the OCCM. Cryo-EM studies of this 14-subunit complex reveal that the two separate heptameric complexes are engaged extensively, with the ORC-Cdc6 N-terminal AAA+ domains latching onto the C-terminal AAA+ motor domains of the MCM2-7 hexamer. The conformation of ORC-Cdc6 undergoes a concerted change into a right-handed spiral with helical symmetry that is identical to that of the DNA double helix. The resulting ORC-Cdc6 helicase loader shows a notable structural similarity to the replication factor C clamp loader, suggesting a conserved mechanism of action

Quantum Correlations in NMR systems

In conventional NMR experiments, the Zeeman energy gaps of the nuclear spin ensembles are much lower than their thermal energies, and accordingly exhibit tiny polarizations. Generally such low-purity quantum states are devoid of quantum entanglement. However, there exist certain nonclassical correlations which can be observed even in such systems. In this chapter, we discuss three such quantum correlations, namely, quantum contextuality, Leggett-Garg temporal correlations, and quantum discord. In each case, we provide a brief theoretical background and then describe some results from NMR experiments.Comment: 21 pages, 7 figure

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s√=8 TeV with the ATLAS detector

The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1fb−1 of proton–proton collision data at √s = 8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via t˜→tχ˜01 or t˜→ bχ˜±1 →bW(∗)χ˜01 , where χ˜01 (χ˜±1 ) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of t˜ → tχ˜01 . For a branching fraction of 100%, top squark masses in the range 270–645 GeV are excluded for χ˜01 masses below 30 GeV. For a branching fraction of 50% to either t˜ → tχ˜01 or t˜ → bχ˜±1 , and assuming the χ˜±1 mass to be twice the χ˜01 mass, top squark masses in the range 250–550 GeV are excluded for χ˜01 masses below 60 GeV

A systematic review of the evidence for single stage and two stage revision of infected knee replacement

BACKGROUND: Periprosthetic infection about the knee is a devastating complication that may affect between 1% and 5% of knee replacement. With over 79 000 knee replacements being implanted each year in the UK, periprosthetic infection (PJI) is set to become an important burden of disease and cost to the healthcare economy. One of the important controversies in treatment of PJI is whether a single stage revision operation is superior to a two-stage procedure. This study sought to systematically evaluate the published evidence to determine which technique had lowest reinfection rates. METHODS: A systematic review of the literature was undertaken using the MEDLINE and EMBASE databases with the aim to identify existing studies that present the outcomes of each surgical technique. Reinfection rate was the primary outcome measure. Studies of specific subsets of patients such as resistant organisms were excluded. RESULTS: 63 studies were identified that met the inclusion criteria. The majority of which (58) were reports of two-stage revision. Reinfection rated varied between 0% and 41% in two-stage studies, and 0% and 11% in single stage studies. No clinical trials were identified and the majority of studies were observational studies. CONCLUSIONS: Evidence for both one-stage and two-stage revision is largely of low quality. The evidence basis for two-stage revision is significantly larger, and further work into direct comparison between the two techniques should be undertaken as a priority

Design and mechanistic insight into ultrafast calcium indicators for monitoring intracellular calcium dynamics.

Calmodulin-based genetically encoded fluorescent calcium indicators (GCaMP-s) are powerful tools of imaging calcium dynamics from cells to freely moving animals. High affinity indicators with slow kinetics however distort the temporal profile of calcium transients. Here we report the development of reduced affinity ultrafast variants of GCaMP6s and GCaMP6f. We hypothesized that GCaMP-s have a common kinetic mechanism with a rate-limiting process in the interaction of the RS20 peptide and calcium-calmodulin. Therefore we targeted specific residues in the binding interface by rational design generating improved indicators with GCaMP6fu displaying fluorescence rise and decay times (t1/2) of 1 and 3 ms (37 °C) in vitro, 9 and 22-fold faster than GCaMP6f respectively. In HEK293T cells, GCaMP6fu revealed a 4-fold faster decay of ATP-evoked intracellular calcium transients than GCaMP6f. Stimulation of hippocampal CA1 pyramidal neurons with five action potentials fired at 100 Hz resulted in a single dendritic calcium transient with a 2-fold faster rise and 7-fold faster decay time (t1/2 of 40 ms) than GCaMP6f, indicating that tracking high frequency action potentials may be limited by calcium dynamics. We propose that the design strategy used for generating GCaMP6fu is applicable for the acceleration of the response kinetics of GCaMP-type calcium indicators

Evaluation of imaging ordering by general practitioners in Australia, 2002–03 to 2011–12

Introdução: A deteção dos abusos contra crianças não é fácil para o médico, pois a história clínica recolhida é muitas vezes enganosa, os achados físicos são muitas vezes inespecíficos e os médicos, na maioria dos casos, não incluem o abuso no diagnóstico diferencial dos quadros clínicos com que se confrontam. Este diagnóstico é particularmente complexo no caso das queimaduras, cujas consequências, pelo menos do ponto de vista psicológico, são sempre graves. Daí a necessidade de cada vez se conhecerem mais profundamente estas situações, nas suas diversas vertentes, em cada país e comunidade, para que as medidas de detenção, diagnósticos e prevenção se possam adequar a cada realidade. Objetivo: Contribuir para conhecer melhor esta realidade e para reforçar a ideia da necessidade urgente da organização dos serviços em Angola, para que as equipas multidisciplinares possam existir e intervir adequada e atempadamente, para bem das vítimas, da comunidade e da justiça. Material e Métodos: Foram estudadas 230 crianças admitidas por queimaduras na Unidade de Queimados do Hospital Neves Bendinha, em Luanda. A ficha de recolha de dados foi preenchida durante o período de internamento das crianças, incluindo dados constantes do processo clínico hospitalar e outros obtidos através da entrevista de um dos progenitores ou representante legal da criança. Resultados e Discussão: As vítimas eram muito novas (50% até aos 5 anos; média de idade 7 anos), encontrando-se 99.6% a cargo dos familiares os quais, em apenas 69% dos casos, foram as pessoas que as levaram ao hospital; 57% não foram levadas ao hospital no dia do evento, sendo que em 77% dos casos este aconteceu em casa. Estes aspetos podem estar relacionados com a tentativa de ocultação dos cassos abusivos. De acordo com os registos clínicos, 47% das queimaduras associava-se a negligência, 33% a acidente e 20% a abuso. A queimadura provocada por imersão em água quente verificou-se em 75% dos casos alegadamente abusivos. Os locais mais atingidos foram os membros superiores (22%), tórax/mamas (22%) e membros inferiores (18%), para todos os casos, verificando-se que a região genital e nádegas sofreu mais queimaduras nas situações alegadamente abusivas (7%). As queimaduras figuradas, apesar de muito escassas no geral, surgiram em 50% dos casos de suspeita de abuso, bem como a distribuição bilateral e simétrica das lesões (em 57% destes casos), o que é altamente sugestivo de lesões intencionalmente infligidas. As queimaduras foram de 2º grau em 65% dos casos, sendo as mais graves nos casos supostamente devidos a abuso; no entanto, foi nestes casos que houve menos atingimento da área corporal (74% até 10% da área corporal), talvez porque a queimadura intencional foi aplicada a uma área concreta. Em 63% dos alegados abusos encontraram-se outras lesões distintas das queimaduras e em 28% cicatrizes de lesões (o que pode traduzir reiteração do abuso). A denúncia da suspeita de abuso foi apresentada em apenas 26% dos casos, o que está de acordo com a ocultação típica destes casos. Os supostos abusadores seriam maioritariamente familiares da vítima e do sexo feminino (58% e 56%), respetivamente, com idade média de 24 anos (20% menores de idade) e em 62% dos casos havia referência a consumo abusivo de álcool. Estes casos seriam melhor apoiados se conseguisse: (1) promover a sua deteção precoce pelos profissionais que trabalham com crianças; (2) incentivar a sinalização/denúncia da sua suspeita por esses mesmos profissionais; (3) a colaboração de especialistas em medicina legal para apoiar o diagnóstico mais seguro dos casos; (4) definir normas procedimentais e protocolos que apoiassem o diagnóstico por esses especialistas e a sua boa articulação com os outros profissionais os quais, no seu conjunto, deveriam constituir uma equipa multidisciplinar de intervenção nestes casos.Introduction: It is difficult for a doctor to detect a children abuse, due to the fact that the history about the event is sometimes not true, the physical findings are usually unspecific, frequently doctors don´t include the abuse in the differential diagnosis. This diagnosis is particularly difficult to perform in burns, which consequences, at least from the psychological point of view, are always severe. That´s why is important to know deeply this situations, in their several strands, in each country and community, so the detection measures, diagnosis and prevention can be adjust to each reality. Objective: To contribute to better understand this reality and to reinforce the necessity to organize the services in Angola, so that the multidisciplinary teams can exist and act in accordance and within a suitable way and schedule, for the welfare of the victims, community and justice. Material and Methods: 230 children were studied; they were admitted in the burn unit from the Hospital Neves Bendinha, in Luanda, Angola. The collection of data forms was fulfilled during the inpatient period; it includes information from their medical historical process and others collected through an interview to the children´s parents or their legal representative. Results and Discussion: The victims are very young (50% until the age of 5; average: 7 years-old), in 99.6% their relatives were in charge, and in only 69% of the cases, the relatives took the children to the hospital; 57% were not taken to the hospital in the day of the event, and in 77% of the cases the event happened at home. These aspects can be related with the attempt to hide these abusive cases. Accordingly to the clinic registrations, 47% of the burns were associated to neglecting acts, 33% to accidents and 20% to abuse. Burns caused by the immersion in hot water were showed in 75% of the alleged abusive cases. The body parts more affected were the upper limbs (22%), chest/breast (22%) and lower limbs (18%), for all the cases; the genital area and buttocks were the regions where more burns were suffered by the alleged abused children (7%). The patterned burns, in spite of being very rare, appeared in 50% of the suspected abuses cases, as well as the bilateral distribution and symmetrical of the burns (in 57% of these cases); these may suggest that the burns were intentional inflicted. The burns were of 2nd degree in 65% of the cases, being the more severe in the abuse cases; however, in these cases there was less body burn (74% until 10% of body area), maybe because the intentional burn was applied in a concrete area. In 63% of the alleged abuses there were other injuries and in 28% scars (that may suggest the reiteration of the abuse). The abuse complaints were presented in only 26% of the cases, which is in accordance with the attempt to hide them. The alleged abusers were mainly the victims’ relatives and the females (58% and 56%, respectively), with an average age of 24 years (20% minors) and in 62% of the cases there was a reference to an abusive alcohol consumption. These cases would be better supported if it was possible to: (1) promote the early detection by the professional that work with children; (2) promote the report of the professionals regarding these events; (3) obtain collaboration from the forensic doctors to support a more secure diagnosis in these cases; (4) set some procedure rules and protocols that can support the diagnosis performed by these physicians and their better cooperation with other professionals, creating together a multidisciplinary team for the intervention in these cases