Direct muscle electrical stimulation as a method for the in vivo assessment of force production in m. abductor hallucis

© 2020 Elsevier Ltd In vivo assessment of the force-generating capacity of m. abductor hallucis (AbH) is problematic due to its combined abduction-flexion action and the inability of some individuals to voluntarily activate the muscle. This study investigated direct muscle electrical stimulation as a method to assess isometric force production in AbH about the 1st metatarsal phalangeal joint (1MPJ) at different muscle-tendon lengths, with the aim of identifying an optimal angle for force production. A 7 s stimulation train was delivered at 20 Hz pulse frequency and sub-maximal (150% motor threshold) intensity to the AbH of the left foot in 16 participants whilst seated, and with the Hallux suspended from a force transducer in 0°,5°,10°,15° and 20° 1MPJ dorsal flexion. Reflective markers positioned on the foot and force transducer were tracked with 5 optical cameras to continuously record the force profile and calculate the external 1MPJ joint flexion moment at each joint configuration. A parabolic relationship was found between AbH force production and 1MPJ configuration. The highest 1MPJ joint moments induced by electrical stimulation were found between 10° and 15° of Hallux dorsal flexion. However, the joint angle (p < 0.001; η2 = 0.86) changed significantly across all but one 1MPJ configurations tested during the stimulation-evoked contraction, resulting in a significant change in the corresponding external moment arm (p < 0.001; η2 = 0.83). Therefore, the changes in joint geometry during contraction should be accounted for to prevent an underestimation of the resulting joint moment. We conclude that direct muscle electrical stimulation combined with dynamometry offers a robust method for standardised assessment of AbH sub-maximal isometric force production

Input states for quantum gates

We examine three possible implementations of non-deterministic linear optical cnot gates with a view to an in-principle demonstration in the near future. To this end we consider demonstrating the gates using currently available sources such as spontaneous parametric down conversion and coherent states, and current detectors only able to distinguish between zero or many photons. The demonstration is possible in the co-incidence basis and the errors introduced by the non-optimal input states and detectors are analysed

The fossil record of early tetrapods: worker effort and the end-Permian mass extinction

It is important to understand the quality of the fossil record of early tetrapods (Tetrapoda, minus Lissamphibia and Amniota) because of their key role in the transition of vertebrates from water to land, their dominance of terrestrial faunas for over 100 million years of the late Palaeozoic and earlyMesozoic, and their variable fates during the end−Permian mass extinction. The first description of an early tetrapod dates back to 1824, and since then discoveries have occurred at a rather irregular pace, with peaks and troughs corresponding to some of the vicissitudes of human history through the past two centuries. As expected, the record is dominated by the well−sampled sedimentary basins of Europe and North America, but finds from other continents are increasing rapidly. Comparisons of snapshots of knowledge in 1900, 1950, and 2000 show that discovery of new species has changed the shape of the species−level diversification curve, contrary to earlier studies of family−level taxa. There is, however, little evidence that taxon counts relate to research effort (as counted by numbers of publications), and there are no biasing effects associated with differential study of different time intervals through the late Palaeozoic and Mesozoic. In fact, levels of effort are apparently not related to geological time, with no evidence that workers have spent more time on more recent parts of the record. In particular, the end−Permian mass extinction was investigated to determine whether diversity changes through that interval might reflect worker effort: it turns out that most records of early tetrapod taxa (when corrected for duration of geological series) occur in the Lower Triassic

PcG Proteins, DNA Methylation, and Gene Repression by Chromatin Looping

Many DNA hypermethylated and epigenetically silenced genes in adult cancers are Polycomb group (PcG) marked in embryonic stem (ES) cells. We show that a large region upstream (∼30 kb) of and extending ∼60 kb around one such gene, GATA-4, is organized—in Tera-2 undifferentiated embryonic carcinoma (EC) cells—in a topologically complex multi-loop conformation that is formed by multiple internal long-range contact regions near areas enriched for EZH2, other PcG proteins, and the signature PcG histone mark, H3K27me3. Small interfering RNA (siRNA)–mediated depletion of EZH2 in undifferentiated Tera-2 cells leads to a significant reduction in the frequency of long-range associations at the GATA-4 locus, seemingly dependent on affecting the H3K27me3 enrichments around those chromatin regions, accompanied by a modest increase in GATA-4 transcription. The chromatin loops completely dissolve, accompanied by loss of PcG proteins and H3K27me3 marks, when Tera-2 cells receive differentiation signals which induce a ∼60-fold increase in GATA-4 expression. In colon cancer cells, however, the frequency of the long-range interactions are increased in a setting where GATA-4 has no basal transcription and the loops encompass multiple, abnormally DNA hypermethylated CpG islands, and the methyl-cytosine binding protein MBD2 is localized to these CpG islands, including ones near the gene promoter. Removing DNA methylation through genetic disruption of DNA methyltransferases (DKO cells) leads to loss of MBD2 occupancy and to a decrease in the frequency of long-range contacts, such that these now more resemble those in undifferentiated Tera-2 cells. Our findings reveal unexpected similarities in higher order chromatin conformation between stem/precursor cells and adult cancers. We also provide novel insight that PcG-occupied and H3K27me3-enriched regions can form chromatin loops and physically interact in cis around a single gene in mammalian cells. The loops associate with a poised, low transcription state in EC cells and, with the addition of DNA methylation, completely repressed transcription in adult cancer cells

Scheme for the implementation of a universal quantum cloning machine via cavity-assisted atomic collisions in cavity QED

We propose a scheme to implement the $1\to2$ universal quantum cloning machine of Buzek et.al [Phys. Rev.A 54, 1844(1996)] in the context of cavity QED. The scheme requires cavity-assisted collision processes between atoms, which cross through nonresonant cavity fields in the vacuum states. The cavity fields are only virtually excited to face the decoherence problem. That's why the requirements on the cavity quality factor can be loosened.Comment: to appear in PR

Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

Decoherence in trapped ions due to polarization of the residual background gas

We investigate the mechanism of damping and heating of trapped ions associated with the polarization of the residual background gas induced by the oscillating ions themselves. Reasoning by analogy with the physics of surface electrons in liquid helium, we demonstrate that the decay of Rabi oscillations observed in experiments on 9Be+ can be attributed to the polarization phenomena investigated here. The measured sensitivity of the damping of Rabi oscillations with respect to the vibrational quantum number of a trapped ion is also predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum

Interface electronic states and boundary conditions for envelope functions

The envelope-function method with generalized boundary conditions is applied to the description of localized and resonant interface states. A complete set of phenomenological conditions which restrict the form of connection rules for envelope functions is derived using the Hermiticity and symmetry requirements. Empirical coefficients in the connection rules play role of material parameters which characterize an internal structure of every particular heterointerface. As an illustration we present the derivation of the most general connection rules for the one-band effective mass and 4-band Kane models. The conditions for the existence of Tamm-like localized interface states are established. It is shown that a nontrivial form of the connection rules can also result in the formation of resonant states. The most transparent manifestation of such states is the resonant tunneling through a single-barrier heterostructure.Comment: RevTeX4, 11 pages, 5 eps figures, submitted to Phys.Rev.

How can power discourses be changed? - Contrasting the ‘daughter deficit’ policy of the Delhi government with Gandhi and King’s transformational reframing

Social policy impact is partly determined by how policy is articulated and advocated, including which values are highlighted and how. In this paper, we examine the influence of policy framing and reframing on outcomes, with particular reference to the policies of the Delhi state government in India that target the practices of female feticide, infanticide and neglect that underlie the ‘daughter deficit’. Using Snow and Benford’s categories for understanding reframing processes, the paper outlines and applies a ‘model’ of reframing disputed issues derived from looking at two famous campaigns – Gandhi’s 1930 Salt March in the struggle for Indian freedom from British rule and the African-American civil rights struggle of the 1950s and 1960s. It argues that ‘carrot and stick’ policy measures, such as financial incentives and legal prohibitions, to counteract the ‘daughter deficit’ must be complemented by well crafted discursive interventions

Emphysema scores predict death from COPD and lung cancer

OBJECTIVE: Our objective was to assess the usefulness of emphysema scores in predicting death from COPD and lung cancer. METHODS: Emphysema was assessed with low-dose CT scans performed on 9,047 men and women for whom age and smoking history were documented. Each scan was scored according to the presence of emphysema as follows: none, mild, moderate, or marked. Follow-up time was calculated from time of CT scan to time of death or December 31, 2007, whichever came first. Cox regression analysis was used to calculate the hazard ratio (HR) of emphysema as a predictor of death. RESULTS: Median age was 65 years, 4,433 (49%) were men, and 4,133 (46%) were currently smoking or had quit within 5 years. Emphysema was identified in 2,637 (29%) and was a significant predictor of death from COPD (HR, 9.3; 95% CI, 4.3-20.2; P < .0001) and from lung cancer (HR, 1.7; 95% CI, 1.1-2.5; P = .013), even when adjusted for age and smoking history. CONCLUSIONS: Visual assessment of emphysema on CT scan is a significant predictor of death from COPD and lung cancer