Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
6,927
result(s) for
"Williams, Joseph"
Sort by:
Substrate Stiffness Controls Osteoblastic and Chondrocytic Differentiation of Mesenchymal Stem Cells without Exogenous Stimuli
Stem cell fate has been linked to the mechanical properties of their underlying substrate, affecting mechanoreceptors and ultimately leading to downstream biological response. Studies have used polymers to mimic the stiffness of extracellular matrix as well as of individual tissues and shown mesenchymal stem cells (MSCs) could be directed along specific lineages. In this study, we examined the role of stiffness in MSC differentiation to two closely related cell phenotypes: osteoblast and chondrocyte. We prepared four methyl acrylate/methyl methacrylate (MA/MMA) polymer surfaces with elastic moduli ranging from 0.1 MPa to 310 MPa by altering monomer concentration. MSCs were cultured in media without exogenous growth factors and their biological responses were compared to committed chondrocytes and osteoblasts. Both chondrogenic and osteogenic markers were elevated when MSCs were grown on substrates with stiffness <10 MPa. Like chondrocytes, MSCs on lower stiffness substrates showed elevated expression of ACAN, SOX9, and COL2 and proteoglycan content; COMP was elevated in MSCs but reduced in chondrocytes. Substrate stiffness altered levels of RUNX2 mRNA, alkaline phosphatase specific activity, osteocalcin, and osteoprotegerin in osteoblasts, decreasing levels on the least stiff substrate. Expression of integrin subunits α1, α2, α5, αv, β1, and β3 changed in a stiffness- and cell type-dependent manner. Silencing of integrin subunit beta 1 (ITGB1) in MSCs abolished both osteoblastic and chondrogenic differentiation in response to substrate stiffness. Our results suggest that substrate stiffness is an important mediator of osteoblastic and chondrogenic differentiation, and integrin β1 plays a pivotal role in this process.
Journal Article
Power imbalance prevents shared decision making
Providing information is not enough to enable shared decision making, argue Natalie Joseph-Williams and colleagues. Action is required to change the attitudes of both patients and doctors
Journal Article
Changes in global nitrogen cycling during the Holocene epoch
A global synthesis of stable nitrogen isotopic values in lacustrine sediments indicates a period of declining enrichment from 15,000 to 7,000 years before present, probably in response to terrestrial carbon sequestration.
The rise and fall of nitrogen availability
Reactive nitrogen supply has increased significantly since the industrial revolution. It remains unclear, however, whether nitrogen availability — the supply of nitrogen relative to the demand from plants and microbes — has increased on a global scale. This study explores patterns of nitrogen cycling during the past 15,000 years with the help of previously published nitrogen isotope data from lake sediments around the world. Kendra McLauchlan
et al
. find that between 15,000 and 7,000 years ago, global terrestrial ecosystems experienced a prolonged decline in nitrogen availability, and propose that this might be the consequence of global changes in carbon dynamics. Surprisingly, there was no coherent trend in nitrogen cycling during the past 500 years, suggesting that modern increases in atmospheric carbon dioxide and net carbon sequestration in the biosphere may have compensated for increased supplies of reactive nitrogen in some ecosystems.
Human activities have doubled the pre-industrial supply of reactive nitrogen on Earth, and future rates of increase are expected to accelerate
1
. Yet little is known about the capacity of the biosphere to buffer increased nitrogen influx. Past changes in global ecosystems following deglaciation at the end of the Pleistocene epoch provide an opportunity to understand better how nitrogen cycling in the terrestrial biosphere responded to changes in carbon cycling. We analysed published records of stable nitrogen isotopic values (δ
15
N) in sediments from 86 lakes on six continents. Here we show that the value of sedimentary δ
15
N declined from 15,000 years before present to 7,056 ± 597 years before present, a period of increasing atmospheric carbon dioxide concentrations and terrestrial carbon accumulation
2
. Comparison of the nitrogen isotope record with concomitant carbon accumulation on land and nitrous oxide in the atmosphere suggests millennia of declining nitrogen availability in terrestrial ecosystems during the Pleistocene–Holocene transition around 11,000 years before present. In contrast, we do not observe a consistent change in global sedimentary δ
15
N values during the past 500 years, despite the potential effects of changing temperature and nitrogen influx from anthropogenic sources. We propose that the lack of a single response may indicate that modern increases in atmospheric carbon dioxide and net carbon sequestration in the biosphere have the potential to offset recent increased supplies of reactive nitrogen in some ecosystems.
Journal Article
الموالد في مصر
لم يكن كتاب \"الموالد\" مجرد وصف للاحتفالات المصرية بذكرى مولد \"ولى\" أو \"أولياء\" لكنه كان سياحة دينية اجتماعية ثقافية في قلب الشارع والحارة المصرية وصف لطباع المصريين عاداتهم أساليب حياتهم أنماط سلوكهم وانطباع الاجنبي في نفس الوقت ازاء هاذا كله نوع من الأفعال وردود الأفعال وهذا كله مغلف بنزعة صوفية اكتسبها الرجل من اختلاطه بالدراويش ورجال الطرائق الصوفية اختلاطا على مستوى الحاية اليومية والمعايشة عن كثب.
Book
A Review of Thermal Property Enhancements of Low-Temperature Nano-Enhanced Phase Change Materials
Phase change materials (PCMs) are of increasing interest due to their ability to absorb and store large amounts of thermal energy, with minimal temperature variations. In the phase-change process, these large amounts of thermal energy can be stored with a minimal change in temperature during both the solid/liquid and liquid/vapor phase transitions. As a result, these PCMs are experiencing increased use in applications such as solar energy heating or storage, building insulation, electronic cooling, food storage, and waste heat recovery. Low temperature, nano-enhanced phase change materials (NEPCM) are of particular interest, due to the recent increase in applications related to the shipment of cellular based materials and vaccines, both of which require precise temperature control for sustained periods of time. Information such as PCM and nanoparticle type, the effective goals, and manipulation of PCM thermal properties are assembled from the literature, evaluated, and discussed in detail, to provide an overview of NEPCMs and provide guidance for additional study. Current studies of NEPCMs are limited in scope, with the primary focus of a majority of recent investigations directed at increasing the thermal conductivity and reducing the charging and discharging times. Only a limited number of investigations have examined the issues related to increasing the latent heat to improve the thermal capacity or enhancing the stability to prevent sedimentation of the nanoparticles. In addition, this review examines several other important thermophysical parameters, including the thermal conductivity, phase transition temperature, rheological affects, and the chemical stability of NEPCMs. This is accomplished largely through comparing of the thermophysical properties of the base PCMs and their nano-enhanced counter parts and then evaluating the relative effectiveness of the various types of NEPCMs. Although there are exceptions, for a majority of conventional heat transfer fluids the thermal conductivity of the base PCM generally increases, and the latent heat decreases as the mass fraction of the nanoparticles increases, whereas trends in phase change temperature are often dependent upon the properties of the individual components. A number of recommendations for further study are made, including a better understanding of the stability of NEPCMs such that sedimentation is limited and thus capable of withstanding long-term thermal cycles without significant degradation of thermal properties, along with the identification of those factors that have the greatest overall impact and which PCM combinations might result in the most significant increases in latent heat.
Journal Article
Explanatorium of the Earth
Packed with fun facts and incredible visuals of everything from supervolcanoes to tsunamis, this is the only Earth encyclopedia for children you'll ever need. What makes volcanoes erupt? Why are tornadoes and hurricanes so destructive? How do rocks, fossils, and gems form? 'Explanatorium of the Earth' takes you on an incredible voyage deep into the heart of our planet and back to discover the powerful forces that continually shape and remodel our ever-changing world. Discover how tectonic plates tear apart and collide, moving millimetre by millimetre to create continents, mountain ranges, oceans, and volcanoes. Witness the destructive power of earthquakes, tsunamis, and hurricanes.
Book
Novelties of the flowering plant pollen tube underlie diversification of a key life history stage
The origin and rapid diversification of flowering plants has puzzled evolutionary biologists, dating back to Charles Darwin. Since that time a number of key life history and morphological traits have been proposed as developmental correlates of the extraordinary diversity and ecological success of angiosperms. Here, I identify several innovations that were fundamental to the evolutionary lability of angiosperm reproduction, and hence to their diversification. In gymnosperms pollen reception must be near the egg largely because sperm swim or are transported by pollen tubes that grow at very slow rates (< [almost equal to]20 μm/h). In contrast, pollen tube growth rates of taxa in ancient angiosperm lineages (Amborella, Nuphar, and Austrobaileya) range from [almost equal to]80 to 600 μm/h. Comparative analyses point to accelerated pollen tube growth rate as a critical innovation that preceded the origin of the true closed carpel, long styles, multiseeded ovaries, and, in monocots and eudicots, much faster pollen tube growth rates. Ancient angiosperm pollen tubes all have callosic walls and callose plugs (in contrast, no gymnosperms have these features). The early association of the callose-walled growth pattern with accelerated pollen tube growth rate underlies a striking repeated pattern of faster and longer-distance pollen tube growth often within solid pathways in phylogenetically derived angiosperms. Pollen tube innovations are a key component of the spectacular diversification of carpel (flower and fruit) form and reproductive cycles in flowering plants.
Journal Article