2,089 research outputs found
New molecular mediators in tumor angiogenesis
Angiogenesis is essential for tumor growth and progression. It has been demonstrated that tumor growth beyond a size 1 to 2 mm3 requires the induction of new vessels. Angiogenesis is regulated by several endogenous stimulators and inhibitors of endothelial cell migration, proliferation and tube formation. Under physiological conditions these mediators of endothelial cell growth are in balance and vessel growth is limited. In fact, within the angiogenic balance endothelial cell turnover is sufficient to maintain a functional vascular wall but does not allow vessel growth. Tumor growth an progression has successfully been correlated to the serum concentration of angiogenic mediators. Furthermore, the vascular density of tumor tissues could be correlated to the clinical course of the disease in several tumor entities. Within the last years several new mediators of endothelial cell growth have been isolated e.g. angiopoietin 1, angiopoietin 2, midkine, pleiotropin, leptin and maspin. In this review we discuss the mechanisms leading to tumor angiogenesis and describe some of the newer mediators of endothelial cell stimulation and inhibition
Regulated Expansion of Electricity Transmission Networks: The Effects of Fluctuating Demand and Wind Generation
We study the performance of different regulatory approaches for the expansion of electricity transmission networks in the light of realistic demand patterns and fluctuating wind power. In particular, we are interested in the relative performance of a combined merchant-regulatory mechanism compared to a cost-based and a merchant-like approach. In contrast to earlier research, we explicitly include both an hourly time resolution and fluctuating wind power, which allows representing demand in a very realistic way. This substantially increases the real-world applicability of results compared to previous analyses, which were based on simplifying assumptions. We show that a combined merchant-regulatory regulation, which draws on a cap over the two-part tariff of the Transco, leads to welfare outcomes far superior to the modeled alternatives. This result proves to be robust over a range of different cases and sensitivity analyses. We also find that the intertemporal rebalancing of the two-part tariff carried out by the Transco so as to expand the network is such that the fixed tariff part turns out to be relatively large compared to extension costs.Electricity, Regulation, Transmission Expansion, Wind Power
Fases prĂ©-analĂtica, analĂtica e pĂłs-analĂtica no monitoramento laboratorial da anticoagulação com antagonistas da vitamina K
A trombose Ă© uma doença caracterizada por eventos de hipercoagulabilidade. A terapĂŞutica anticoagulante oral com antagonistas da vitamina K (AVKs) Ă© amplamente indicada para prevenção e/ou controle de distĂşrbios da coagulação. O manuseio de administração dos AVKs Ă© difĂcil devido Ă complexidade da definição da dose. Em geral, o monitoramento de indivĂduos submetidos Ă terapĂŞutica com AVK Ă© realizado pela determinação do tempo de protrombina, em que se avalia o grau de anticoagulação atravĂ©s do coeficiente internacional normatizado. Invariavelmente, o fluxo do processamento laboratorial, que compreende as fases prĂ©-analĂtica, analĂtica e pĂłs-analĂtica, Ă© importante para a fidedignidade dos resultados, repercutindo na conduta mĂ©dica de forma determinante. O objetivo deste estudo foi a realização de uma revisĂŁo da literatura cientĂfica descritiva utilizando bases de dados eletrĂ´nicos para busca de materiais cientĂficos, como Google Scholar, MEDLINE, LILACS, PubMed, SciELO e Science Direct. Abordamos alguns aspectos relacionados ao fluxo analĂtico da monitoração laboratorial em um laboratĂłrio de análises clĂnicas. Em conclusĂŁo, Ă© necessária uma apropriada condução das fases analĂticas para que seja possĂvel o sucesso terapĂŞutico com uso dos AVKs.
Palavras-chave: Tempo de protrombina; coeficiente internacional normatizado; fases analĂtica
Single-center experience with mechanical valve replacement in children and adolescents : a lifelong challenge
A Best Practice Example from Diatom Research
DNA barcoding uses a short fragment of a DNA sequence to identify a taxon.
After obtaining the target sequence it is compared to reference sequences
stored in a database to assign an organism name to it. The quality of data in
the reference database is the key to the success of the analysis. In the here
presented study, multiple types of data have been combined and critically
examined in order to create best practice guidelines for taxonomic reference
libraries for environmental barcoding. 70 unialgal diatom strains from Berlin
waters have been established and cultured to obtain morphological and
molecular data. The strains were sequenced for 18S V4 rDNA (the pre-Barcode
for protists) as well as rbcL data, and identified by microscopy. LM and for
some strains also SEM pictures were taken and physical vouchers deposited at
the BGBM. 37 freshwater taxa from 15 naviculoid diatom genera were identified.
Four taxa from the genera Amphora, Mayamaea, Planothidium and Stauroneis are
described here as new. Names, molecular, morphological and habitat data as
well as additional images of living cells are also available electronically in
the AlgaTerra Information System. All reference sequences (or reference
barcodes) presented here are linked to voucher specimens in order to provide a
complete chain of evidence back to the formal taxonomic literature
Impact of warming events on reef-scale temperature variability as captured in two Little Cayman coral Sr/Ca records
The rising temperature of the world’s oceans is affecting coral reef ecosystems by increasing
the frequency and severity of bleaching and mortality events. The susceptibility of corals to temperature stress varies on local and regional scales. Insights into potential controlling parameters are hampered by a
lack of long term in situ data in most coral reef environments and sea surface temperature (SST) products often do not resolve reef-scale variations. Here we use 42 years (1970–2012) of coral Sr/Ca data to reconstruct seasonal- to decadal-scale SST variations in two adjacent but distinct reef environments at Little Cayman, Cayman Islands. Our results indicate that two massive Diploria strigosa corals growing in the lagoon and in the fore reef responded differently to past warming events. Coral Sr/Ca data from the shallow lagoon successfully record high summer temperatures confirmed by in situ observations (>338C). Surprisingly, coral Sr/Ca from the deeper fore reef is strongly affected by thermal stress events, although seasonal temperature extremes and mean SSTs at this site are reduced compared to the lagoon. The shallow lagoon coral showed decadal variations in Sr/Ca, supposedly related to the modulation of lagoonal temperature through varying tidal water exchange, influenced by the 18.6 year lunar nodal cycle. Our results show that reef-scale SST variability can be much larger than suggested by satellite SST measurements. Thus, using coral SST proxy records from different reef zones combined with in situ observations will improve conservation programs that are developed to monitor and predict potential thermal stress on coral reefs
Integrative taxonomic description of two new species of the Cocconeis placentula group (Bacillariophyceae) from Korea based on unialgal strains
Cocconeis coreana and C. sijunghoensis are described as new based on micromorphological and molecular data C. coreana is represented by five unialgal cultures from four different freshwater bodies, two from North Korea and three from South Korea. C. sijunghoensis is represented by two unialgal cultures from a brackish water body in North Korea. Except for one, all of the strains auxosporulated and showed an almost quadrupling of size in length and width. Morphologically, these species with their two different elliptical valves belong to the Cocconeis placentula group. The raphe valve has striae with uniseriate areolae continuing across a pronounced submarginal hyaline rim to the edge of the valve. The sternum valve has uniseriate dash-like areolae continuously from the valve face until the valve edge. Micromorphologically, these species possess two different open valvocopulae: only the raphe valvocopula has fimbriae; the sternum valvocopula has none. Based on p-distances of currently available DNA sequence data, i.e., rbcL and 18SV4, both species are pronouncedly different from the epitype strain of C. placentula, with C. coreana closest to the published molecular data of the strain UTEX FD23 named C. placentula from Iowa, USA, while C. sijunghoensis is closest but not the same as the publ is hed molecular data of strain D36_012, the epitype strain of C. placentula from Berlin, Germany. Based on scanning elect ron microscope observations, differentiating features are discussed concerning valvocopula fimbriae, central area, areolation of the sternum valve and on the raphe valve especially between the submarginal hyaline rim and edge
Ultrafast optical ranging using microresonator soliton frequency combs
Light detection and ranging (LIDAR) is critical to many fields in science and
industry. Over the last decade, optical frequency combs were shown to offer
unique advantages in optical ranging, in particular when it comes to fast
distance acquisition with high accuracy. However, current comb-based concepts
are not suited for emerging high-volume applications such as drone navigation
or autonomous driving. These applications critically rely on LIDAR systems that
are not only accurate and fast, but also compact, robust, and amenable to
cost-efficient mass-production. Here we show that integrated dissipative
Kerr-soliton (DKS) comb sources provide a route to chip-scale LIDAR systems
that combine sub-wavelength accuracy and unprecedented acquisition speed with
the opportunity to exploit advanced photonic integration concepts for
wafer-scale mass production. In our experiments, we use a pair of free-running
DKS combs, each providing more than 100 carriers for massively parallel
synthetic-wavelength interferometry. We demonstrate dual-comb distance
measurements with record-low Allan deviations down to 12 nm at averaging times
of 14 s as well as ultrafast ranging at unprecedented measurement rates of
up to 100 MHz. We prove the viability of our technique by sampling the
naturally scattering surface of air-gun projectiles flying at 150 m/s (Mach
0.47). Combining integrated dual-comb LIDAR engines with chip-scale
nanophotonic phased arrays, the approach could allow widespread use of compact
ultrafast ranging systems in emerging mass applications.Comment: 9 pages, 3 figures, Supplementary information is attached in
'Ancillary files
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