658 research outputs found
Economic Diversification Supported the Growth of Mongolia’s Nomadic Empires
Populations in Mongolia from the late second millennium B.C.E. through the Mongol Empire are traditionally assumed, by archaeologists and historians, to have maintained a highly specialized horse-facilitated form of mobile pastoralism. Until recently, a dearth of direct evidence for prehistoric human diet and subsistence economies in Mongolia has rendered systematic testing of this view impossible. Here, we present stable carbon and nitrogen isotope measurements of human bone collagen, and stable carbon isotope analysis of human enamel bioapatite, from 137 well-dated ancient Mongolian individuals spanning the period c. 4400 B.C.E. to 1300 C.E. Our results demonstrate an increase in consumption of C4 plants beginning at c. 800 B.C.E., almost certainly indicative of millet consumption, an interpretation supported by archaeological evidence. The escalating scale of millet consumption on the eastern Eurasian steppe over time, and an expansion of isotopic niche widths, indicate that historic Mongolian empires were supported by a diversification of economic strategies rather than uniform, specialized pastoralism
Random field sampling for a simplified model of melt-blowing considering turbulent velocity fluctuations
In melt-blowing very thin liquid fiber jets are spun due to high-velocity air
streams. In literature there is a clear, unsolved discrepancy between the
measured and computed jet attenuation. In this paper we will verify numerically
that the turbulent velocity fluctuations causing a random aerodynamic drag on
the fiber jets -- that has been neglected so far -- are the crucial effect to
close this gap. For this purpose, we model the velocity fluctuations as vector
Gaussian random fields on top of a k-epsilon turbulence description and develop
an efficient sampling procedure. Taking advantage of the special covariance
structure the effort of the sampling is linear in the discretization and makes
the realization possible
The effect of crab burrows on soil-water dynamics in mangroves
Many mangrove ecosystem services, such as carbon sequestration, are closely linked to mangrove soil water content, which in turn is thought to depend on animal burrow density and the properties of the sediment in which the burrows are constructed. We measured the water content in the sediment matrix between crab burrows across 26 plots in a typical, fine-grained (clay), mangrove soil in the Mekong Delta, Vietnam. We found that the water content of the sediment matrix remained more or less constant throughout the tidal cycle, and was independent of burrow density. Our results suggest that there is little exchange of water between the burrows and the associated sediment matrix and that burrows act as an independent pipe network transporting water through the mangrove soil. To check and extend our findings, we used a numerical groundwater model to simulate an idealized burrow in a range of sediment types. The model results confirmed that fine-grained mangrove sediments do not drain readily into adjacent animal burrows because of their very low permeability. Our results have important implications for understanding and forecasting mangrove carbon dynamics with sea level rise
Low Complexity Regularization of Linear Inverse Problems
Inverse problems and regularization theory is a central theme in contemporary
signal processing, where the goal is to reconstruct an unknown signal from
partial indirect, and possibly noisy, measurements of it. A now standard method
for recovering the unknown signal is to solve a convex optimization problem
that enforces some prior knowledge about its structure. This has proved
efficient in many problems routinely encountered in imaging sciences,
statistics and machine learning. This chapter delivers a review of recent
advances in the field where the regularization prior promotes solutions
conforming to some notion of simplicity/low-complexity. These priors encompass
as popular examples sparsity and group sparsity (to capture the compressibility
of natural signals and images), total variation and analysis sparsity (to
promote piecewise regularity), and low-rank (as natural extension of sparsity
to matrix-valued data). Our aim is to provide a unified treatment of all these
regularizations under a single umbrella, namely the theory of partial
smoothness. This framework is very general and accommodates all low-complexity
regularizers just mentioned, as well as many others. Partial smoothness turns
out to be the canonical way to encode low-dimensional models that can be linear
spaces or more general smooth manifolds. This review is intended to serve as a
one stop shop toward the understanding of the theoretical properties of the
so-regularized solutions. It covers a large spectrum including: (i) recovery
guarantees and stability to noise, both in terms of -stability and
model (manifold) identification; (ii) sensitivity analysis to perturbations of
the parameters involved (in particular the observations), with applications to
unbiased risk estimation ; (iii) convergence properties of the forward-backward
proximal splitting scheme, that is particularly well suited to solve the
corresponding large-scale regularized optimization problem
アデノシルコバラミン関与ジオールデヒドラターゼの再活性化因子に関する研究
OBJECTIVE: To determine the extent to which prostheses with no readily available evidence to support their use are being implanted in primary total hip arthroplasty. DESIGN: Systematic review of the literature. DATA SOURCES: The 9th annual report of the National Joint Registry of England and Wales (NJR) was analysed to identify prostheses with an Orthopaedic Data Evaluation Panel rating of "unclassified" or "pre-entry" used in primary total hip arthroplasty in 2011. A systematic review of those prostheses was carried out using PubMed, Cochrane, Embase, OVID, and Google databases. STUDY SELECTION: Prostheses used in primary total hip arthroplasty as published in the NJR's 9th annual report were analysed. Only literature that included the name of the prosthesis was included. Literature yielded in the search results was excluded if it reported animal, non-orthopaedic, non-total hip arthroplasty, or non-device related studies. RESULTS: The systematic review found that 24% (57/235) of all hip replacement implants available to surgeons in the UK have no evidence for their clinical effectiveness. It also shows that 10,617 (7.8%) of the 136,593 components used in primary hip replacements in 2011 were implanted without readily identifiable evidence of clinical effectiveness. These comprised 157 cemented stems (0.5% of 34,655 implanted), 936 (2.8% of 33,367) uncemented stems, 1732 (7.1% of 24,349) cemented cups, and 7577 (17.1% of 44,222) uncemented cups. CONCLUSIONS: This study shows that a considerable proportion of prostheses available to orthopaedic surgeons have no readily available evidence of clinical effectiveness to support their use. Concern exists about the current system of device regulation, and the need for a revised process for introducing new orthopaedic devices is highlighted
Detector Description and Performance for the First Coincidence Observations between LIGO and GEO
For 17 days in August and September 2002, the LIGO and GEO interferometer
gravitational wave detectors were operated in coincidence to produce their
first data for scientific analysis. Although the detectors were still far from
their design sensitivity levels, the data can be used to place better upper
limits on the flux of gravitational waves incident on the earth than previous
direct measurements. This paper describes the instruments and the data in some
detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial
change
Success or failure of primary second/foreign language programmes in Asia: What do the data tell us?
Primary school second/foreign language (SL/FL) programmes in Asia, as well as in other parts of the world, are becoming more common, with many targeting English as the SL or FL. The pressures for such English language programmes come from top-down notions that in a globalised world English is required for societies to be competitive, especially with Asian neighbours, and bottom-up pressures from parents who see English as the key to educational success for their children. In many polities, these forces have resulted in support for policies that introduce early primary school English teaching curricula for all students and have led to parents spending large sums of money on private tutoring or out-of-school tuition. This study reviews the results of nine language planning studies from the Asian region that set out to examine questions such as 'Is this trend towards early primary SL or FL education (mainly English) realistic or is it unattainable and a waste of resources? Do children really benefit from these programmes? What needs to be done to foster learners' success?' These issues are viewed from a language planning and policy perspective through an examination of the language-in-education policy types required for the development of successful programmes. The policies of a number of Asian countries are used as case studies to illustrate this issue
Hypertension and one-year risk of all-cause mortality among women with treated HIV in the United States
Objective: Hypertension is a critical cause of cardiovascular disease, and women with HIV have a higher prevalence of hypertension than women without HIV. The relationship between hypertension and mortality has not been well characterized in women with treated HIV. Here, we estimate the effect of hypertension on 1-year risk of all-cause mortality among women with HIV on antiretroviral therapy (ART) in the United States. Design: An analysis of multicenter, observational cohort data from the Women's Interagency HIV Study (WIHS) collected between 1995 and 2019. Methods: We included women with HIV who reported ever using ART. We used parametric g-computation to estimate the effect of hypertension (SBP ≥140 mmHg, DBP ≥90 mmHg, or use of hypertensive medication) on all-cause mortality within 1 year of a WIHS visit. Results: Among 2929 unique women, we included 57 034 visits with a median age of 45 (interquartile range: 39, 52) years. Women had hypertension at 34.5% of visits, and 641 deaths occurred within 1 year of a study visit. Comparing women at visits with hypertension to women at visits without hypertension, the standardized 1-year risk ratio for mortality was 1.16 [95% confidence interval (95% CI): 1.01-1.33]. The risk ratios were higher in Hispanic (risk ratio: 1.23, 95% CI: 0.86-1.77) and non-Hispanic black women (risk ratio: 1.19, 95% CI: 1.04-1.37) and lower in non-Hispanic white women (risk ratio: 0.93, 95% CI: 0.58-1.48). Conclusion: Among women with treated HIV, those with hypertension, compared with those without, had an increased 1-year risk of all-cause mortality
- …