2,390 research outputs found
Could cancer drugs provide ammunition against aging?
Recent advances in our understanding of the molecular and cellular signaling pathways that drive aging have revealed several genetic and environmental manipulations that can increase lifespan across different species. Research on the underlying biology of aging has not only revealed it to be a biologically malleable process but has also paved the way for the development of pharmacological interventions that could increase lifespan and delay the onset and/or progression of age-related disease
A2: Smalls Falls Revisted: A Journey Through a Paleozoic Sedimentary Basin
Guidebook for field trips in Western Maine and Northern New Hampshire: New England Intercollegiate Geological Conference, p. 35-60
Lattice thermal conductivity of disordered NiPd and NiPt alloys
Numerical calculations of lattice thermal conductivity are reported for the
binary alloys NiPd and NiPt. The present work is a continuation of an earlier
paper by us [PRB, 72, 214207 (2005)]which had developed a theoretical framework
for the calculation of configuration-averaged lattice thermal conductivity and
thermal diffusivity in disordered alloys. The formulation was based on the
augmented space theorem combined with a scattering diagram technique. In this
paper we shall show dependence of the lattice thermal conductivity on a series
of variables like phonon frequency, temperature and alloy composition. The
temperature dependence of and its realtion to the measured thermal
conductivity is discussed. The concentration dependence of appears to
justify the notion of a minimum thermal conductivity as discussed by Kittel,
Slack and others. We also study the frequency and composition dependence of the
thermal diffusivity averaged over modes. A numerical estimate of this quantity
gives an idea about the location of mobility edge and the fraction of states in
the frequency spectrum which is delocalized.Comment: 23 pages, 18 figure
Thermoelectric transport in strained Si and Si/Ge heterostructures
The anisotropic thermoelectric transport properties of bulk silicon strained
in [111]-direction were studied by detailed first-principles calculations
focussing on a possible enhancement of the power factor. Electron as well as
hole doping were examined in a broad doping and temperature range. At low
temperature and low doping an enhancement of the power factor was obtained for
compressive and tensile strain in the electron-doped case and for compressive
strain in the hole-doped case. For the thermoelectrically more important high
temperature and high doping regime a slight enhancement of the power factor was
only found under small compressive strain with the power factor overall being
robust against applied strain. To extend our findings the anisotropic
thermoelectric transport of an [111]-oriented Si/Ge superlattice was
investigated. Here, the cross-plane power factor under hole-doping was
drastically suppressed due to quantum-well effects, while under electron-doping
an enhanced power factor was found. With that, we state a figure of merit of
ZT and ZT at T=\unit[300]{K} and T=\unit[900]{K} for the
electron-doped [111]-oriented Si/Ge superlattice. All results are discussed in
terms of band structure features
Glass-Like Heat Conduction in High-Mobility Crystalline Semiconductors
The thermal conductivity of polycrystalline semiconductors with type-I
clathrate hydrate crystal structure is reported. Ge clathrates (doped with Sr
and/or Eu) exhibit lattice thermal conductivities typical of amorphous
materials. Remarkably, this behavior occurs in spite of the well-defined
crystalline structure and relatively high electron mobility (). The dynamics of dopant ions and their interaction with the
polyhedral cages of the structure are a likely source of the strong phonon
scattering.Comment: 4 pages, 3 postscript figures, to be published, Phys. Rev. Let
Effects of social capital on operational performance: impacts of servitisation
Studies on servitisation have largely overlooked the roles of social capital with suppliers and knowledge management. We propose a moderated mediation model to investigate the impacts of servitisation on the mechanisms through which social capital with suppliers improves operational performance. The hypotheses are empirically tested using structural equation modelling and data collected from 276 manufacturing firms in China. The results show that social capital improves operational performance both directly and indirectly through knowledge management, and the relationships are influenced by servitisation. In particular, social capital improves operational performance directly and indirectly through knowledge combination in servitised firms, whereas social capital only improves operational performance indirectly through knowledge acquisition in traditional manufacturers. The findings contribute to the literature by revealing that the effects of social capital with suppliers on operational performance are partially mediated by knowledge acquisition and knowledge combination and the mediation effects are moderated by servitisation, and by providing insights into how to design purchasing and production systems to profit from servitisation
Characteristics and serotype distribution of childhood cases of invasive pneumococcal disease following pneumococcal conjugate vaccination in England and Wales, 2006-14
Background The 7-valent (PCV7) and 13-valent (PCV13) pneumococcal conjugate vaccines are
highly effective in preventing invasive pneumococcal disease (IPD) caused by vaccine serotypes.
Vaccine failure (vaccine-type IPD after age-appropriate immunisation) is rare. Little is known about
the risk, clinical characteristics or outcomes of PCV13 compared to PCV7 vaccine failure.
Methods Public Health England conducts IPD surveillance and provides a national reference
service for serotyping pneumococcal isolates in England and Wales. We compared the
epidemiology, rates, risk factors, serotype distribution, clinical characteristics, and outcomes of IPD
in children with PCV13 and PCV7 vaccine failure.
Results A total of 163 episodes of PCV failure were confirmed in 161 children over eight years (04
September 2006 to 03 September 2014) in ten birth cohorts. After three vaccine doses, PCV7 and
PCV13 failure rates were 0.19/100,000 (95% CI, 0.10-0.33; 57 cases) and 0.66/100,000 (95% CI,
0.44-0.99; 104 cases) vaccinated person-years, respectively. Children with PCV13 failure were
more likely to be healthy (87/105 [82.9%] vs. 37/56 [66.1%]; P=0.02), present with bacteremic lower
respiratory tract infection (61/105 [58.1%] vs. 11/56 [19.6%]; P<0.001) and develop empyema
(41/61 [67.2%] vs. 1/11 [9.1%]; P<0.001) compared to PCV7 failures. Serotypes 3 (n=38, 36.2%)
and 19A (n=30, 28.6%) were responsible for most PCV13 failures. Five children died (3.1%; 95%
CI, 1.0-7.1%), including four with co-morbidities.
Conclusions PCV failure is rare and, compared to PCV7 serotypes, the additional PCV13
serotypes are more likely to cause bacteremic lower respiratory tract infection and empyema in
healthy vaccinated children
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