237 research outputs found
Detailed analysis of the cell-inactivation mechanism by accelerated protons and light ions
Published survival data for V79 cells irradiated by monoenergetic protons,
helium-3, carbon, and oxygen ions and for CHO cells irradiated by carbon ions
have been analyzed using the probabilistic two-stage model of cell
inactivation. Three different classes of DNA damages formed by traversing
particles have been distinguished, namely severe single-track damages which
might lead to cell inactivation directly, less severe damages where cell
inactivation is caused by their combinations, and damages of negligible
severity that can be repaired easily. Probabilities of single ions to form
these damages have been assessed in dependence on their linear energy transfer
(LET) values.
Damage induction probabilities increase with atomic number and LET. While
combined damages play crucial role at lower LET values, single-track damages
dominate in high-LET regions. The yields of single-track lethal damages for
protons have been compared with the Monte Carlo estimates of complex DNA
lesions, indicating that lethal events correlate well with complex DNA
double-strand breaks. The decrease in the single-track damage probability for
protons of LET above approx. 30 keV/m, suggested by limited experimental
evidence, is discussed, together with the consequent differences in the
mechanisms of biological effects between protons and heavier ions. Applications
of the results in hadrontherapy treatment planning are outlined.Comment: submitted to Physics in Medicine and Biolog
Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes
Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density
Tensorial form and matrix elements of the relativistic nuclear recoil operator
Within the lowest-order relativistic approximation () and to
first order in , the tensorial form of the relativistic corrections of
the nuclear recoil Hamiltonian is derived, opening interesting perspectives for
calculating isotope shifts in the multiconfiguration Dirac-Hartree-Fock
framework. Their calculation is illustrated for selected Li-, B- and C-like
ions. The present work underlines the fact that the relativistic corrections to
the nuclear recoil are definitively necessary for getting reliable isotope
shift values.Comment: 22 pages, no figures, submitted to J. Phys.
An Integrated Framework for Intersectorality: Nonprofitness and Its Influence on Society and Public Administration Programs
Cross-sector interactions have long occurred in the public delivery of goods, services, and interests. While scholars have often addressed cross-sector interactions using the dimensions of publicness (state) and privateness (market), an intersectoral framework necessitates the understanding and incorporation of nonprofitness to account for the dimensions of nonprofits along the public-private continuum. This article proposes a framework for identifying the dimensions of nonprofits in an intersectoral world and draws on relevant examples to illustrate the presence and influence of nonprofitness. The article then focuses on the future of education in the field of public administration and, in light of the proposed framework, makes and considers recommendations to help educational programs better equip students to appreciate work across sectors
A review on boiling heat transfer enhancement with nanofluids
There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement
Activation of Thromboxane A2 Receptor (TP) Increases the Expression of Monocyte Chemoattractant Protein -1 (MCP-1)/Chemokine (C-C motif) Ligand 2 (CCL2) and Recruits Macrophages to Promote Invasion of Lung Cancer Cells
Thromboxane synthase (TXAS) and thromboxane A2 receptor (TP), two critical components for thromboxane A2 (TXA2) signaling, have been suggested to be involved in cancer invasion and metastasis. However, the mechanisms by which TXA2 promotes these processes are still unclear. Here we show that TXA2 mimetic, I-BOP, induced monocyte chemoattractant protein -1(MCP-1)/chemokine (C-C motif) ligand 2 (CCL2) expression at both mRNA and protein levels in human lung adenocarcinoma A549 cells stably over-expressing TP receptor α isoform (A549-TPα). The induction of MCP-1 was also found in other lung cancer cells H157 and H460 that express relatively high levels of endogenous TP. Using specific inhibitors of several signaling molecules and promoter/luciferase assay, we identified that transcription factor SP1 mediates I-BOP-induced MCP-1 expression. Furthermore, supernatants from I-BOP-treated A549-TPα cells enhanced MCP-1-dependent migration of RAW 264.7 macrophages. Moreover, co-culture of A549 cells with RAW 264.7 macrophages induced expression of MMPs, VEGF and MCP-1 genes, and increased the invasive potential in A549 cells. These findings suggest that TXA2 may stimulate invasion of cancer cells through MCP-1-mediated macrophage recruitment
A Set of 100 Chloroplast DNA Primer Pairs to Study Population Genetics and Phylogeny in Monocotyledons
Chloroplast DNA sequences are of great interest for population genetics and phylogenetic studies. However, only a small set of markers are commonly used. Most of them have been designed for amplification in a large range of Angiosperms and are located in the Large Single Copy (LSC). Here we developed a new set of 100 primer pairs optimized for amplification in Monocotyledons. Primer pairs amplify coding (exon) and non-coding regions (intron and intergenic spacer). They span the different chloroplast regions: 72 are located in the LSC, 13 in the Small Single Copy (SSC) and 15 in the Inverted Repeat region (IR). Amplification and sequencing were tested in 13 species of Monocotyledons: Dioscorea abyssinica, D. praehensilis, D. rotundata, D. dumetorum, D. bulbifera, Trichopus sempervirens (Dioscoreaceae), Phoenix canariensis, P. dactylifera, Astrocaryum scopatum, A. murumuru, Ceroxylon echinulatum (Arecaceae), Digitaria excilis and Pennisetum glaucum (Poaceae). The diversity found in Dioscorea, Digitaria and Pennisetum mainly corresponded to Single Nucleotide Polymorphism (SNP) while the diversity found in Arecaceae also comprises Variable Number Tandem Repeat (VNTR). We observed that the most variable loci (rps15-ycf1, rpl32-ccsA, ndhF-rpl32, ndhG-ndhI and ccsA) are located in the SSC. Through the analysis of the genetic structure of a wild-cultivated species complex in Dioscorea, we demonstrated that this new set of primers is of great interest for population genetics and we anticipate that it will also be useful for phylogeny and bar-coding studies
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