Constructing Incremental Sequences in Graphs

Given a weighted graph , we investigate the problem of constructing a sequence of subsets of vertices (called groups) with small diameters, where the diameter of a group is calculated using distances in G. The constraint on these n groups is that they must be incremental: . The cost of a sequence is the maximum ratio between the diameter of each group Mi and the diameter of a group with I vertices and minimum diameter: . This quantity captures the impact of the incremental constraint on the diameters of the groups in a sequence. We give general bounds on the value of this ratio and we prove that the problem of constructing an optimal incremental sequence cannot be solved approximately in polynomial time with an approximation ratio less than 2 unless P = NP. Finally, we give a 4-approximation algorithm and we show that the analysis of our algorithm is tight

THz On-Chip Waveguides for Ultrafast Magnetic Measurements

This thesis describes the development of on-chip terahertz (THz) waveguides for use in ultrafast magnetic measurements. An epitaxial transfer method is used to bond photoconductive switch material to quartz substrates. This, combined with optical lithography methods, allows on-chip generation and detection of THz pulses. Normally, the metal in a waveguide has a high conductivity (eg. gold or copper) in order to reduce ohmic loss. However, if this metal is instead a magnetic multilayer, then the THz pulse interaction with the metal can be used to measure ultrafast magnetic effects. This was performed using Cobalt/Copper multilayers, and a THz GMR was seen in a transmitted pulse. Additionally, an ’inverse’ GMR was noted in input pulses and in the pulse tail of transmitted pulses. It is believed that this is the first time such behaviour has been documented. Lateral spin valves offer the ability to separate charge and spin effects; however, the dimensions of these devices is in the hundreds of nanometers range. Coplanar waveguides were used to confine and concentrate THz pulses into this spatial regime. Curved waveguides were fabricated to prove confinement, and magnetoresistance properties were used to demonstrate field concentration. Devices were then designed to allow picosecond current injection into a lateral spin valve geometry. Initial results are obscured due to interference from the excitation pulse, but improvements to the design and fabrication could pave the way for this technology in the future

Metformin-associated lactic acidosis in an intensive care unit

International audienceIntroduction Metformin-associated lactic acidosis (MALA) is aclassic side effect of metformin and is known to be a severedisease with a high mortality rate. The treatment of MALA withdialysis is controversial and is the subject of many case reportsin the literature. We aimed to assess the prevalence of MALA ina 16-bed, university-affiliated, intensive care unit (ICU), and theeffect of dialysis on patient outcome.Methods Over a five-year period, we retrospectively identifiedall patients who were either admitted to the ICU with metforminas a usual medication, or who attempted suicide by metforminingestion. Within this population, we selected patientspresenting with lactic acidosis, thus defining MALA, anddescribed their clinical and biological features.Results MALA accounted for 0.84% of all admissions duringthe study period (30 MALA admissions over five years) and wasassociated with a 30% mortality rate. The only factorsassociated with a fatal outcome were the reason for admissionin the ICU and the initial prothrombin time. Although patientswho went on to haemodialysis had higher illness severity scores,as compared with those who were not dialysed, the mortalityrates were similar between the two groups (31.3% versus28.6%).Conclusions MALA can be encountered in the ICU severaltimes a year and still remains a life-threatening condition.Treatment is restricted mostly to supportive measures, althoughhaemodialysis may possess a protective effect

NADPH oxidase deficiency results in reduced alveolar macrophage 5â lipoxygenase expression and decreased leukotriene synthesis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141933/1/jlb1585.pd

Enhancing the connection between the classroom and the clinical workplace:A systematic review

Introduction Although medical students are increasingly exposed to clinical experiences as part of their training, these often occur parallel with, rather than connected to, their classroom-based learning experiences. Additionally, students seem to struggle with spontaneously making the connection between these spheres of their training themselves. Therefore, this systematic review synthesized the existing evidence about educational interventions that aim to enhance the connection between learning in the classroom and its application in the workplace. Methods Electronic databases (AMED, CINAHL, EMBASE, ERIC, Medline, RDRB, PsycINFO and WoS) were screened for quantitative and qualitative studies investigating educational interventions that referenced a connection between the classroom and workplace-based experiences within undergraduate, graduate or postgraduate medical education. Results Three types of interventions were identified: classroom to workplace interventions, workplace to classroom interventions, and interventions involving multiple connections between the two settings. Most interventions involved a tool (e.g. video, flow chart) or a specific process (e.g. linking patient cases with classroom-based learning content, reflecting on differences between what was learned and how it works in practice) which aimed to enhance the connection between the two settings. Discussion Small-scale interventions can bring classroom learning and workplace practice into closer alignment. Such interventions appear to be the necessary accompaniments to curricular structures, helping bridge the gap between classroom learning and workplace experience. This paper documents examples that may serve to assist medical educators in connecting the classroom and the workplace

Cooperation and Deception Recruit Different Subsets of the Theory-of-Mind Network

The term “theory of mind” (ToM) describes an evolved psychological mechanism that is necessary to represent intentions and expectations in social interaction. It is thus involved in determining the proclivity of others to cooperate or defect. While in cooperative settings between two parties the intentions and expectations of the protagonists match, they diverge in deceptive scenarios, in which one protagonist is intentionally manipulated to hold a false belief about the intention of the other. In a functional magnetic resonance imaging paradigm using cartoons showing social interactions (including the outcome of the interaction) between two or three story characters, respectively, we sought to determine those brain areas of the ToM network involved in reasoning about cooperative versus deceptive interactions. Healthy volunteers were asked to reflect upon the protagonists' intentions and expectations in cartoons depicting cooperation, deception or a combination of both, where two characters cooperated to deceive a third. Reasoning about the mental states of the story characters yielded substantial differences in activation patterns: both deception and cooperation activated bilateral temporoparietal junction, parietal and cingulate regions, while deception alone additionally recruited orbitofrontal and medial prefrontal regions. These results indicate an important role for prefrontal cortex in processing a mismatch between a character's intention and another's expectations as required in complex social interactions

Universal transport signatures in two-electron molecular quantum dots: gate-tunable Hund's rule, underscreened Kondo effect and quantum phase transitions

We review here some universal aspects of the physics of two-electron molecular transistors in the absence of strong spin-orbit effects. Several recent quantum dots experiments have shown that an electrostatic backgate could be used to control the energy dispersion of magnetic levels. We discuss how the generically asymmetric coupling of the metallic contacts to two different molecular orbitals can indeed lead to a gate-tunable Hund's rule in the presence of singlet and triplet states in the quantum dot. For gate voltages such that the singlet constitutes the (non-magnetic) ground state, one generally observes a suppression of low voltage transport, which can yet be restored in the form of enhanced cotunneling features at finite bias. More interestingly, when the gate voltage is controlled to obtain the triplet configuration, spin S=1 Kondo anomalies appear at zero-bias, with non-Fermi liquid features related to the underscreening of a spin larger than 1/2. Finally, the small bare singlet-triplet splitting in our device allows to fine-tune with the gate between these two magnetic configurations, leading to an unscreening quantum phase transition. This transition occurs between the non-magnetic singlet phase, where a two-stage Kondo effect occurs, and the triplet phase, where the partially compensated (underscreened) moment is akin to a magnetically "ordered" state. These observations are put theoretically into a consistent global picture by using new Numerical Renormalization Group simulations, taylored to capture sharp finie-voltage cotunneling features within the Coulomb diamonds, together with complementary out-of-equilibrium diagrammatic calculations on the two-orbital Anderson model. This work should shed further light on the complicated puzzle still raised by multi-orbital extensions of the classic Kondo problem.Comment: Review article. 16 pages, 17 figures. Minor corrections and extra references added in V

Masirah – The other Oman ophiolite: A better analogue for mid-ocean ridge processes?

Oman has two ophiolites – the better known late Cretaceous northern Oman (or Semail) ophiolite and the lesser known and smaller, Jurassic Masirah ophiolite located on the eastern coast of the country adjacent to the Indian Ocean. A number of geological, geochronological and geochemical lines of evidence strongly suggest that the northern Oman ophiolite did not form at a mid-ocean ridge but rather in a supra-subduction zone setting by fast spreading during subduction initiation. In contrast the Masirah ophiolite is structurally part of a series of ophiolite nappes which are rooted in the Indian Ocean floor. There are significant geochemical differences between the Masirah and northern Oman ophiolites and none of the supra-subduction features typical of the northern Oman ophiolite are found at Masirah. Geochemically Masirah is MORB, although in detail it contains both enriched and depleted MORB reflecting a complex source for the lavas and dykes. The enrichment of this source predates the formation of the ophiolite. The condensed crustal section on Masirah (ca 2 km) contains a very thin gabbro sequence and is thought to reflect its genesis from a cool mantle source associated with the early stages of sea-floor spreading during the early separation of eastern and western Gondwana. These data suggest that the Masirah ophiolite is a suitable analogue for an ophiolite created at a mid-ocean ridge, whereas the northern Oman ophiolite is not. The stratigraphic history of the Masirah ophiolite shows that it remained a part of the oceanic crust for ca 80 Ma. The chemical variability and enrichment of the Masirah lavas is similar to that found elsewhere in Indian Ocean basalts and may simply reflect a similar provenance rather than a feature fundamental to the formation of the ophiolite.University of Derb

Indication of insensitivity of planetary weathering behavior and habitable zone to surface land fraction

It is likely that unambiguous habitable zone terrestrial planets of unknown water content will soon be discovered. Water content helps determine surface land fraction, which influences planetary weathering behavior. This is important because the silicate weathering feedback determines the width of the habitable zone in space and time. Here a low-order model of weathering and climate, useful for gaining qualitative understanding, is developed to examine climate evolution for planets of various land-ocean fractions. It is pointed out that, if seafloor weathering does not depend directly on surface temperature, there can be no weathering-climate feedback on a waterworld. This would dramatically narrow the habitable zone of a waterworld. Results from our model indicate that weathering behavior does not depend strongly on land fraction for partially ocean-covered planets. This is powerful because it suggests that previous habitable zone theory is robust to changes in land fraction, as long as there is some land. Finally, a mechanism is proposed for a waterworld to prevent complete water loss during a moist greenhouse through rapid weathering of exposed continents. This process is named a "waterworld self-arrest," and it implies that waterworlds can go through a moist greenhouse stage and end up as planets like Earth with partial ocean coverage. This work stresses the importance of surface and geologic effects, in addition to the usual incident stellar flux, for habitability.Comment: 15 pages, 6 figures, accepted at Ap