1,922 research outputs found
Timing of Spermarche and Menarche are Associated with Physical Activity and Sedentary Behavior Among Korean Adolescents
OBJECTIVES: This study examined the timing of menarche and spermarche and their associations with physical activity (PA) and sedentary behavior (SB) after controlling for body mass index (BMI). METHODS: Multiple logistic regression analyses were conducted to determine whether the timing of menarche in girls and spermarche in boys is associated with PA and SB independent of BMI in a nationally representative sample of Korean adolescents (13–18 years; N = 74,186). RESULTS: After controlling for age, family economic status, and BMI, early timing of spermarche among boys was associated with a higher likelihood of engaging in PA and a lower likelihood of engaging in SB for < 2 hours during weekdays. By contrast, boys with late timing of spermarche were less likely to engage in PA and more likely to engage in SB for < 2 hours. Among girls, early or late timing of menarche was associated with a higher likelihood of engaging in PA and a lower likelihood of engaging in SB. CONCLUSION: Timing of menarche in girls and spermarche in boys could be a marker for PA and SB among Korean adolescents. To promote PA and discourage SB among Korean adolescents, school-based, grade-specific interventions can be tailored by the absence or presence of menarche/spermarche
Understanding high-risk behavior among non-dominant minorities: A social resistance framework
http://dx.doi.org/10.1016/j.socscimed.2011.07.02
Economic opportunity, health behaviours, and health outcomes in the USA: a population-based cross-sectional study
Background Inequality of opportunity, defined as differences in the prospects for upward social mobility, might have important consequences for health. Diminished opportunity can lower the motivation to invest in future health by reducing economic returns to health investments and undermining hope. We estimated the association between county-level economic opportunity and individual-level health in young adults in the general US population. Methods In this population-based cross-sectional study, we used individual-level data from the 2009–12 United States Behavioral Risk Factor Surveillance Surveys. Our primary outcomes were current self-reported overall health and the number of days of poor physical and mental health in the last month. Economic opportunity was measured by the county-averaged national income rank attained by individuals born to families in the lowest income quartile. We restricted our sample to adults aged 25–35 years old to match the data used to assign exposure. Multivariable ordinary least squares and probit models were used to estimate the association between the outcomes and economic opportunity. We adjusted for a range of demographic and socioeconomic characteristics, including age, sex, race, education, income, access to health care, area income inequality, segregation, and social capital. Findings We assessed nearly 147 000 individuals between the ages of 25 years and 35 years surveyed from 2009 to 2012. In models adjusting for individual-level demographics and county-level socioeconomic characteristics, increases in county-level economic opportunity were associated with greater self-reported overall health. An interdecile increase in economic opportunity was associated with 0·76 fewer days of poor mental health (95% CI −1·26 to −0·25) and 0·53 fewer days of poor physical health (−0·96 to −0·09) in the last month. The results were robust to sensitivity analyses. Interpretation Economic opportunity is independently associated with self-reported health and health behaviours. Policies seeking to expand economic opportunities might have important spillover effects on health. Funding Robert Wood Johnson Foundation Health and Society Scholars Program
Quantum non-malleability and authentication
In encryption, non-malleability is a highly desirable property: it ensures
that adversaries cannot manipulate the plaintext by acting on the ciphertext.
Ambainis, Bouda and Winter gave a definition of non-malleability for the
encryption of quantum data. In this work, we show that this definition is too
weak, as it allows adversaries to "inject" plaintexts of their choice into the
ciphertext. We give a new definition of quantum non-malleability which resolves
this problem. Our definition is expressed in terms of entropic quantities,
considers stronger adversaries, and does not assume secrecy. Rather, we prove
that quantum non-malleability implies secrecy; this is in stark contrast to the
classical setting, where the two properties are completely independent. For
unitary schemes, our notion of non-malleability is equivalent to encryption
with a two-design (and hence also to the definition of Ambainis et al.). Our
techniques also yield new results regarding the closely-related task of quantum
authentication. We show that "total authentication" (a notion recently proposed
by Garg, Yuen and Zhandry) can be satisfied with two-designs, a significant
improvement over the eight-design construction of Garg et al. We also show
that, under a mild adaptation of the rejection procedure, both total
authentication and our notion of non-malleability yield quantum authentication
as defined by Dupuis, Nielsen and Salvail.Comment: 20+13 pages, one figure. v2: published version plus extra material.
v3: references added and update
Characterisation and Mechanical Testing of Hydrothermally Treated HA/ZrO2 Composites
Hydrothermal treatment is traditionally employed to improve the sinterability of powder compacts by reducing porosity and increasing apparent density. The effect of hydrothermal treatment on green powder compacts has been assessed in order to better understand how treatment may affect the sinter ability of the bodies. Laboratory synthesized nano sized hydroxyapatite (HA) and a commercial zirconia (ZrO2) powder have been ball milled together to create composite mixtures containing 0-5 wt% ZrO2 loadings. Disc shaped bodies have been formed using uniaxial and subsequent isostatic pressure. The resultant coherent samples were subjected to hydrothermal treatment at either 120 or 250°C for 10 h in order to assess the effect of this processing technique on the physical, mechanical and microstructural properties of the green composites. ZrO2 loadings up to 3 wt% increased apparent density from 90 to 92%, whereas increased loading to 5 wt% increased flexural strength, from 6 to 9 MPa. Increasing the hydrothermal treatment temperature increased open porosity, from ~44 to ~48% and reduced biaxial flexural strengths of the treated bodies compared to those of their room temperature isostatically pressed counterparts (~10 to ~6 MPa). © 2009 Springer Science+Business Media, LLC
Increased Risk of Respiratory Mortality Associated with the High-Tech Manufacturing Industry: A 26-Year Study
Global high-tech manufacturers are mainly located in newly industrialized countries, raising concerns about adverse health consequences from industrial pollution for people living nearby. We investigated the ecological association between respiratory mortality and the development of Taiwan's high-tech manufacturing, taking into account industrialization and socioeconomic development, for 19 cities and counties-6 in the science park group and 13 in the control group-from 1982 to 2007. We applied a linear mixed-effects model to analyze how science park development over time is associated with age-adjusted and sex-specific mortality rates for asthma and chronic obstructive pulmonary disease (COPD). Asthma and female COPD mortality rates decreased in both groups, but they decreased 9%-16% slower in the science park group. Male COPD mortality rates increased in both groups, but the rate increased 10% faster in the science park group. Science park development over time was a significant predictor of death from asthma (p ≤ 0.0001) and COPD (p = 0.0212). The long-term development of clustered high-tech manufacturing may negatively affect nearby populations, constraining health advantages that were anticipated, given overall progress in living standards, knowledge, and health services. National governments should incorporate the long-term health effects on local populations into environmental impact assessments
On the Mass of Population III Stars
Performing 1D hydrodynamical calculations coupled with non-equilibrium
processes for H2 formation, we pursue the thermal and dynamical evolution of
filamentary primordial clouds and attempt to make an estimate on the mass of
population III stars. It is found that, almost independent of initial
conditions, a filamentary cloud continues to collapse nearly isothermally due
to H_2 cooling until the cloud becomes optically thick against the H_2 lines.
During the collapse the cloud structure separates into two parts, i.e., a
denser spindle and a diffuse envelope. The spindle contracts quasi-statically,
and thus the line mass of the spindle keeps a characteristic value determined
solely by the temperature ( K). Applying a linear theory, we find
that the spindle is unstable against fragmentation during the collapse. The
wavelength of the fastest growing perturbation lessens as the collapse
proceeds. Consequently, successive fragmentation could occur. When the central
density exceeds , the successive fragmentation may
cease since the cloud becomes opaque against the H_2 lines and the collapse
decelerates appreciably. The mass of the first star is then expected to be
typically , which may grow up to by accreting
the diffuse envelope. Thus, the first-generation stars are anticipated to be
massive but not supermassive.Comment: 23 pages, 6 figures, accepted by ApJ (April 10
On the Power of Quantum Encryption Keys
The standard definition of quantum state randomization, which is the quantum
analog of the classical one-time pad, consists in applying some transformation
to the quantum message conditioned on a classical secret key . We
investigate encryption schemes in which this transformation is conditioned on a
quantum encryption key state instead of a classical string, and extend
this symmetric-key scheme to an asymmetric-key model in which copies of the
same encryption key may be held by several different people, but
maintaining information-theoretical security. We find bounds on the message
size and the number of copies of the encryption key which can be safely created
in these two models in terms of the entropy of the decryption key, and show
that the optimal bound can be asymptotically reached by a scheme using
classical encryption keys. This means that the use of quantum states as
encryption keys does not allow more of these to be created and shared, nor
encrypt larger messages, than if these keys are purely classical.Comment: 17 pages, 1 figur
Detection of diffuse TeV gamma-ray emission from the nearby starburst galaxy NGC 253
We report the TeV gamma-ray observations of the nearby normal spiral galaxy
NGC 253. At a distance of 2.5 Mpc, NGC 253 is one of the nearest
starburst galaxies. This relative closeness, coupled with the high star
formation rate in the galaxy, make it a good candidate TeV gamma-ray source.
Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m
imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at
the level with a flux of at energies 0.5 TeV. The data indicate that the
emission region is broader than the point spread function of our telescope.Comment: 4 pages, double colomn, 3 figures, aa.cl
Computational Indistinguishability between Quantum States and Its Cryptographic Application
We introduce a computational problem of distinguishing between two specific
quantum states as a new cryptographic problem to design a quantum cryptographic
scheme that is "secure" against any polynomial-time quantum adversary. Our
problem, QSCDff, is to distinguish between two types of random coset states
with a hidden permutation over the symmetric group of finite degree. This
naturally generalizes the commonly-used distinction problem between two
probability distributions in computational cryptography. As our major
contribution, we show that QSCDff has three properties of cryptographic
interest: (i) QSCDff has a trapdoor; (ii) the average-case hardness of QSCDff
coincides with its worst-case hardness; and (iii) QSCDff is computationally at
least as hard as the graph automorphism problem in the worst case. These
cryptographic properties enable us to construct a quantum public-key
cryptosystem, which is likely to withstand any chosen plaintext attack of a
polynomial-time quantum adversary. We further discuss a generalization of
QSCDff, called QSCDcyc, and introduce a multi-bit encryption scheme that relies
on similar cryptographic properties of QSCDcyc.Comment: 24 pages, 2 figures. We improved presentation, and added more detail
proofs and follow-up of recent wor
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