1,081 research outputs found
Gestation and the evolution of vertical stance bipedal humans
During mammalian gestation a change in maternal stance alters the velocities of maternal blood flows and results in a changed rate of delivery and distribution of nutrients required to form the bone and tissue in various parts of a developing foetus. The latter in turn results in change in the extent and position of tissue and bone formation in the foetus. It is shown that such changes would, over many generations, alter the physical characteristics of the ancestor offspring under conditions where the pregnant maternal ancestor normally exhibiting horizontal stance was constrained to adopt a vertical stance for all or most of the gestation period. This behaviour produced the physical characteristics seen in humans and other Hominidae primates, including the vertical stance and bipedalism of the former accompanied by increase in skull and brain size. The manner in which difficulties of giving birth as the change from horizontal stance to vertical stance proceeded from generation to generation, limited survival is discussed andreasons for the adoption of this behaviour are proposed. The induction of evolutionary change and the operation of natural selection through alterations in the characteristics of embryo/foetus of an animal, induced by physical, chemical, mechanical or behavioural means, is shown to be feasible. The changes are not related to the Lamarckian principle of inheritance of acquired characteristics as the changes described occurred before birth and are not related to any physical or mental characteristics already present in or acquired during the lifetime of the breeding pair
Approaching zero : temporal effects of a restrictive antibiotic policy on hospital-acquired Clostridium difficile, extended-spectrum β-lactamase-producing coliforms and meticillin-resistant Staphylococcus aureus
A restrictive antibiotic policy banning routine use of ceftriaxone and ciprofloxacin was implemented in a 450-bed district general hospital following an educational campaign. Monthly consumption of nine antibiotics was monitored in defined daily doses (DDDs) per 1000 patient-occupied bed-days (1000 pt-bds) 9 months before until 16 months after policy introduction. Hospital-acquired Clostridium difficile, meticillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum -lactamase (ESBL)- producing coliform cases per month/1000 pt-bds were identified and reviewed throughout the hospital. Between the first and final 6 months of the study, average monthly consumption of ceftriaxone reduced by 95% (from 46.213 to 2.129 DDDs/1000 pt-bds) and that for ciprofloxacin by 72.5% (109.804 to 30.205 DDDs/1000 pt-bds). Over the same periods, hospital-acquisition rates for C. difficile reduced by 77% (2.398 to 0.549 cases/1000 pt-bds), for MRSA by 25% (1.187 to 0.894 cases/1000 pt-bds) and for ESBL-producing coliforms by 17% (1.480 to 1.224 cases/1000 pt-bds). Time-lag modelling confirmed significant associations between ceftriaxone and C. difficile cases at 1 month (correlation 0.83; P < 0.005), and between ciprofloxacin and ESBL-producing coliform cases at 2 months (correlation 0.649; P = 0.002). An audit performed 3 years after the policy showed sustained reduction in C. difficile rates (0.259 cases/1000 pt-bds), with additional decreases for MRSA (0.409 cases/1000 pt-bds) and ESBL-producing coliforms (0.809 cases/1000 pt-bds). In conclusion, banning two antibiotics resulted in an immediate and profound reduction in hospital-acquired C. difficile, with possible longer-term effects on MRSA and ESBL-producing coliform rates. Antibiotic stewardship is fundamental in the control of major hospital pathogens
Connecting Terminals and 2-Disjoint Connected Subgraphs
Given a graph and a set of terminal vertices we say that a
superset of is -connecting if induces a connected graph, and
is minimal if no strict subset of is -connecting. In this paper we prove
that there are at most minimal -connecting sets when and that
these can be enumerated within a polynomial factor of this bound. This
generalizes the algorithm for enumerating all induced paths between a pair of
vertices, corresponding to the case . We apply our enumeration algorithm
to solve the {\sc 2-Disjoint Connected Subgraphs} problem in time
, improving on the recent algorithm of Cygan et
al. 2012 LATIN paper.Comment: 13 pages, 1 figur
Evaluating Sensitivities of Economic Factors through Coupled Economics-ALMANAC Model System
Using crop models to simulate crop growth and productivity at a regional scale is a complex process designed to represent the observed impact of individual farmer decision-making on the agricultural landscape. Typically, during agricultural simulation efforts, the planting acreages have largely been based on a set of predetermined, static scenarios. In this study, we developed a system to dynamically enhance the Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) crop simulation model through a two-way linkage with an economics land-use model. This coupled model approach integrated farmers’ land-use choices based on relative economic returns and produced dynamic land-use probabilities for ALMANAC simulations through a feedback loop. The coupled model approach was intercompared with static crop modeling through a historic acreage approach, and comparable accuracies were found from both modeling efforts for the 2014 growing season. Furthermore, as a proof-of-concept effort, the method was applied to evaluate the impact of two scenarios on crop simulations: major crops (maize, soybean, and wheat) intensification through price increases (e.g., market change) and incentivized grassland conservation (e.g., policy change). The results of this sensitivity study suggest that the coupled system has the capability to integrate economic factors into traditional crop simulation, allowing for insight into the impacts of changes in markets and policies on agricultural landscapes and crop yields
Propagation inhibition and wave localization in a 2D random liquid medium
Acoustic propagation and scattering in water containing many parallel
air-filled cylinders is studied. Two situations are considered and compared:
(1) wave propagating through the array of cylinders, imitating a traditional
experimental setup, and (2) wave transmitted from a source located inside the
ensemble. We show that waves can be blocked from propagation by disorders in
the first scenario, but the inhibition does not necessarily imply wave
localization. Furthermore, the results reveal the phenomenon of wave
localization in a range of frequencies.Comment: Typos in Fiures are correcte
Gravitation and inertia; a rearrangement of vacuum in gravity
We address the gravitation and inertia in the framework of 'general gauge
principle', which accounts for 'gravitation gauge group' generated by hidden
local internal symmetry implemented on the flat space. We connect this group to
nonlinear realization of the Lie group of 'distortion' of local internal
properties of six-dimensional flat space, which is assumed as a toy model
underlying four-dimensional Minkowski space. The agreement between proposed
gravitational theory and available observational verifications is satisfactory.
We construct relativistic field theory of inertia and derive the relativistic
law of inertia. This theory furnishes justification for introduction of the
Principle of Equivalence. We address the rearrangement of vacuum state in
gravity resulting from these ideas.Comment: 17 pages, no figures, revtex4, Accepted for publication in Astrophys.
Space Sc
Point estimation for adaptive trial designs II: practical considerations and guidance
In adaptive clinical trials, the conventional end-of-trial point estimate of a treatment effect is prone to bias, that is, a systematic tendency to deviate from its true value. As stated in recent FDA guidance on adaptive designs, it is desirable to report estimates of treatment effects that reduce or remove this bias. However, it may be unclear which of the available estimators are preferable, and their use remains rare in practice. This article is the second in a two-part series that studies the issue of bias in point estimation for adaptive trials. Part I provided a methodological review of approaches to remove or reduce the potential bias in point estimation for adaptive designs. In part II, we discuss how bias can affect standard estimators and assess the negative impact this can have. We review current practice for reporting point estimates and illustrate the computation of different estimators using a real adaptive trial example (including code), which we use as a basis for a simulation study. We show that while on average the values of these estimators can be similar, for a particular trial realization they can give noticeably different values for the estimated treatment effect. Finally, we propose guidelines for researchers around the choice of estimators and the reporting of estimates following an adaptive design. The issue of bias should be considered throughout the whole lifecycle of an adaptive design, with the estimation strategy prespecified in the statistical analysis plan. When available, unbiased or bias-reduced estimates are to be preferred
Optimisation of assessment of maximal rate of heart rate increase for tracking training-induced changes in endurance exercise performance
The maximal rate of heart rate (HR) increase (rHRI), a marker of HR acceleration during transition from rest to submaximal exercise, correlates with exercise performance. In this cohort study, whether rHRI tracked performance better when evaluated over shorter time-periods which include a greater proportion of HR acceleration and less steady-state HR was evaluated. rHRI and five-km treadmill running time-trial performance (5TTT) were assessed in 15 runners following one week of light training (LT), two weeks of heavy training (HT) and 10-day taper (T). rHRI was the first derivative maximum of a sigmoidal curve fit to one, two, three and four minutes of R-R data during transition from rest to running at 8 km/h (rHRI8 km/h), 10.5 km/h, 13 km/h and transition from 8 to 13 km/h (rHRI8-13km/h). 5TTT time increased from LT to HT (effect size [ES] 1.0, p < 0.001) then decreased from HT to T (ES -1.7, p < 0.001). 5TTT time was inversely related to rHRI8 km/h assessed over two (B = -5.54, p = 0.04) three (B = -5.34, p = 0.04) and four (B = -5.37, p = 0.04) minutes, and rHRI8-13km/h over one (B = -11.62, p = 0.006) and three (B = -11.44, p = 0.03) minutes. 5TTT correlated most consistently with rHRI8 km/h. rHRI8 km/h assessed over two to four minutes may be suitable for evaluating athlete responses to training.Maximillian J. Nelson, Clint R. Bellenger, Rebecca L. Thomson, Eileen Y. Robertson, Kade Davison, Daniela Schäfer Olstad, Jonathan D. Buckle
WMAP constraints on scalar-tensor cosmology and the variation of the gravitational constant
We present observational constraints on a scalar-tensor gravity theory by
test for CMB anisotropy spectrum. We compare the WMAP temperature
power spectrum with the harmonic attractor model, in which the scalar field has
its harmonic effective potential with curvature in the Einstein
conformal frame and the theory relaxes toward Einstein gravity with time. We
found that the present value of the scalar coupling, i.e. the present level of
deviation from Einstein gravity , is bounded to be smaller than
(), and () for . This constraint is much stronger than the bound from the solar
system experiments for large models, i.e., and 0.3 in
and limits, respectively. Furthermore, within the framework
of this model, the variation of the gravitational constant at the recombination
epoch is constrained as , and
.Comment: 7 page
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