Highlights • Regional and network functional changes could be seen in the early stage of SCI. • Functional changes were associated with clinical symptom severity in SCI patients. • Functional ...reorganization may reflect a compensatory role in the recovery of SCI.
Central Asia is currently a semiarid‐arid region, dominated by the Westerlies. It is important to understand mechanisms of climate and precipitation changes here, as water availability in the region ...is crucial today and in the future. High‐resolution, absolutely‐dated oxygen isotope (δ18O) records of stalagmites from Kesang Cave characterize a dynamic precipitation history over most of the past 500,000 years. This record demonstrates, for the first time, that climate change in the region exhibits a processional rhythm with abrupt inceptions of low δ18O speleothem growth at times of high Northern Hemisphere summer insolation followed by gradual δ18O increases that track decreases of insolation. These observations and interpretations contrast with the interpretation of nearby, but higher elevation ice core records. The absolutely‐dated caveδ18O shifts can be used to correlate the regional climate variability by providing chronological marks. Combined with other paleoclimate records, the Kesang observations suggest that possible incursions of Asian summer monsoon rainfall or related moisture into the Kesang site and/or adjacent areas during the high insolation times may play an important role in changing orbital‐scale hydrology of the region. Based on our record, arid climate will prevail in this region for the next several millennia, providing that anthropogenic effects do not supersede natural processes.
Key Points
Speleothem records characterize 500 ka precipitation history in Central Asia
Climatic patterns in the Westerlies region are dominated by a precession rhythm
Asian Monsoon incursions may explain the hydrological change on precession scale
The stellar initial mass function (IMF) is commonly assumed to be an invariant probability density distribution function of initial stellar masses. These initial stellar masses are generally ...represented by the canonical IMF, which is defined as the result of one star formation event in an embedded cluster. As a consequence, the galaxy-wide IMF (gwIMF) should also be invariant and of the same form as the canonical IMF; gwIMF is defined as the sum of the IMFs of all star-forming regions in which embedded clusters form and spawn the galactic field population of the galaxy. Recent observational and theoretical results challenge the hypothesis that the gwIMF is invariant. In order to study the possible reasons for this variation, it is useful to relate the observed IMF to the gwIMF. Starting with the IMF determined in resolved star clusters, we apply the IGIMF-theory to calculate a comprehensive grid of gwIMF models for metallicities, Fe/H ∈ (−3, 1), and galaxy-wide star formation rates (SFRs), SFR ∈ (10−5, 105) M⊙ yr−1. For a galaxy with metallicity Fe/H < 0 and SFR > 1 M⊙ yr−1, which is a common condition in the early Universe, we find that the gwIMF is both bottom light (relatively fewer low-mass stars) and top heavy (more massive stars), when compared to the canonical IMF. For a SFR < 1 M⊙ yr−1 the gwIMF becomes top light regardless of the metallicity. For metallicities Fe/H > 0 the gwIMF can become bottom heavy regardless of the SFR. The IGIMF models predict that massive elliptical galaxies should have formed with a gwIMF that is top heavy within the first few hundred Myr of the life of the galaxy and that it evolves into a bottom heavy gwIMF in the metal-enriched galactic centre. Using the gwIMF grids, we study the SFR−Hα relation and its dependency on metallicity and the SFR. We also study the correction factors to the Kennicutt SFRK − Hα relation and provide new fitting functions. Late-type dwarf galaxies show significantly higher SFRs with respect to Kennicutt SFRs, while star-forming massive galaxies have significantly lower SFRs than hitherto thought. This has implications for gas-consumption timescales and for the main sequence of galaxies. We explicitly discuss Leo P and ultra-faint dwarf galaxies.
Aim
Emerging evidence from epidemiologic studies and basic science suggests a potential antitumour effect of metformin. However, whether metformin improves survival in cancer patients remains ...inconclusive.
Methods
A literature search was performed using the PubMed, EMbase and SciVerse Scopus databases. Pooled effect estimates were derived using a random‐effects meta‐analysis model.
Results
Of the 28 studies retrieved, the pooled effect estimates showed that metformin was associated with lower risk of all‐cause mortality in cancer patients with concurrent diabetes, particularly for breast pooled relative risk (RR) 0.70, 95% CI 0.55, 0.88; p = 0.003, colorectal (RR 0.70, 95% CI 0.59, 0.84; p < 0.001), ovarian (RR 0.44, 95% CI 0.30, 0.64; p < 0.001) and endometrial cancer (RR 0.49, 95% CI 0.32, 0.73; p = 0.001). In addition, metformin was associated with lower risks of cancer‐specific mortality.
Conclusions
The findings of this study support the hypothesis that metformin improves the survival for cancer patients with concurrent diabetes, particularly for breast, colorectal, ovarian, and endometrial cancer. Further investigation is warranted.
Abstract
We use state-of-the-art chemical models to track the cosmic evolution of the CNO isotopes in the interstellar medium of galaxies, yielding powerful constraints on their stellar initial mass ...function (IMF). We re-assess the relative roles of massive stars, asymptotic giant branch (AGB) stars and novae in the production of rare isotopes such as 13C, 15N, 17O and 18O, along with 12C, 14N and 16O. The CNO isotope yields of super-AGB stars, novae and fast-rotating massive stars are included. Having reproduced the available isotope enrichment data in the solar neighbourhood, and across the Galaxy, and having assessed the sensitivity of our models to the remaining uncertainties, e.g. nova yields and star formation history, we show that we can meaningfully constrain the stellar IMF in galaxies using C, O and N isotope abundance ratios. In starburst galaxies, where data for multiple isotopologue lines are available, we find compelling new evidence for a top-heavy stellar IMF, with profound implications for their star formation rates and efficiencies, perhaps also their stellar masses. Neither chemical fractionation nor selective photodissociation can significantly perturb globally averaged isotopologue abundance ratios away from the corresponding isotope ones, as both these processes will typically affect only small mass fractions of molecular clouds in galaxies. Thus, the Atacama Large Millimeter
Array now stands ready to probe the stellar IMF, and even the ages of specific starburst events in star-forming galaxies across cosmic time unaffected by the dust obscuration effects that plague optical/near-infrared studies.
The cyclic deformation and damage behaviors of the Fe–Mn and Fe–Mn–C TRIP/TWIP steels are comprehensively studied in a wide range of strain amplitude (from 0.3% to 8.0%). It is found that with ...increasing C content, the dislocation structures change from wavy slip to planar slip after cyclic deformation. In order to evaluate the low-cycle and extremely-low-cycle fatigue (LCF and ELCF) properties, a fatigue life prediction model, Nf = (Wa/W0)β, with a hysteresis energy-based criterion is used and developed. The model reveals that the LCF and ELCF damage mechanisms can be controlled by the material's damage capacity (the intrinsic fatigue toughness W0) and its ability of transforming mechanical work into effective damage (the damage transition exponent β). From a macroscopic point of view, W0 is related to the match of strength and ductility (approximately the static toughness U), and β mainly has a negative correlation with the cyclic strain hardening exponent n′. On the micro-scale level, W0 represents the defect-accommodated ability of the materials, and β is determined by the uniformity and reversibility of plastic deformation. For the current Fe–Mn(–C) TRIP/TWIP steels with increasing C content, the cooperation between an increasing damage capacity and an incremental damage accumulation rate leads to a higher ELCF property and a lower LCF property.
The low-cycle fatigue (LCF) damage mechanisms may be controlled by the material's damage capacity and damage accumulation rate. The influences of planar slip caused by short-range order (SRO) on fatigue damage and cracking are quite different from those caused by lowering the stacking fault energy (SFE), which has its origin from the various effects on damage accumulation rate. Display omitted
In recent years, online retailers (also called e-tailers) have started allowing manufacturers direct access to their customers while charging a fee for providing this access, a format commonly ...referred to as agency selling. In this paper, we use a stylized theoretical model to answer a key question that e-tailers are facing: When should they use an agency selling format instead of using the more conventional reselling format? We find that agency selling is more efficient than reselling and leads to lower retail prices; however, the e-tailers end up giving control over retail prices to the manufacturer. Therefore, the reaction by the manufacturer, who makes electronic channel pricing decisions based on their impact on demand in the traditional channel (brick-and-mortar retailing), is an important factor for e-tailers to consider. We find that when sales in the electronic channel lead to a negative effect on demand in the traditional channel, e-tailers prefer agency selling, whereas when sales in the electronic channel lead to substantial stimulation of demand in the traditional channel, e-tailers prefer reselling. This preference is mediated by competition between e-tailers—as competition between them increases, e-tailers prefer to use agency selling. We also find that when e-tailers benefit from positive externalities from the sales of the focal product (such as additional profits from sales of associated products), retail prices may be lower under reselling than under agency selling, and the e-tailers prefer reselling under some conditions for which they would prefer agency selling without the positive externalities.
This paper was accepted by Chris Forman, information systems.
The North China Plain (NCP) is a region with high level of seismic hazard. Previous Global Positioning System measurements, however, have shown a near absence of present‐day crustal deformation. ...Using updated Global Positioning System data covering three blocks of the eastern China, we discover that interseismic deformation in the NCP takes place in an ~1,100 km wide left‐lateral shear zone of roughly east‐west orientation. The 6.0 ± 1.3 mm/yr interseismic left‐lateral shear over the NCP results in contemporary deformation that is eventually accommodated by earthquake ruptures of right‐lateral strike‐slip along the north‐northeast trending faults and anticlockwise block rotates. We suggest that rapid eastward motion of the rigid South China block, with respect to the rigid Amurian block, has created a left‐lateral shear couple to twist the nonrigid NCP to form the contemporary deformation.
Key Points
North China Plain is a region with high‐level of earthquake hazard but absence of detectable crustal deformation
Interseismic deformation of the NCP takes place in an ~1,100 km wide left‐lateral shear zone of roughly east‐west orientation
Permanent right‐lateral slips and block rotates on the NNE‐trending faults accommodate the left‐lateral transient shearing
The extremely-low-cycle fatigue (ELCF) behaviors of pure Cu and Cu–Al alloys are comprehensively studied following the cyclic push–pull loading tests with extremely high strain amplitudes (up to ...±9.5%). Compared with the common low-cycle fatigue (LCF) region, several unique features in the ELCF regime can be noticed, including the deviations of fatigue life from the Coffin–Manson law, the non-negligible proportion occupied by the cyclic hardening stage of the whole fatigue life, special microstructures formed by cyclic loading containing deformation twins, shear bands and ultra-fine grains and the transformation of fatigue cracking modes. All these characteristics indicate the existence of special interior fatigue damage mechanisms of ELCF. To help discover the new damage mechanisms under ELCF, a model of fatigue life prediction with a hysteresis energy-based criterion is proposed. Based on the analysis of the experimental and modeling results, two intrinsic factors determining the ELCF properties were concluded: the capacity of ELCF damage, and the defusing and dispersion ability of the external mechanical work. The former can be evaluated by a parameter of the model called the intrinsic fatigue toughness W0, which is related to the microstructure evolution condition, the cyclic hardening ability, the deformation homogeneity and possibly the static toughness. The latter can be represented by the damage transition exponent β, which can be enhanced by improving the planarity, reversibility and uniformity of plastic deformation, reflecting the decline in the degree of surface damage and the dispersion of fatigue cracks. For Cu–Al alloys with increasing Al content, cooperation between an increasing damage capacity and a decreasing damage accumulation rate leads to a comprehensive improvement in the ELCF properties.
PDF
