561 research outputs found
Molecular dynamics simulations of lead clusters
Molecular dynamics simulations of nanometer-sized lead clusters have been
performed using the Lim, Ong and Ercolessi glue potential (Surf. Sci. {\bf
269/270}, 1109 (1992)). The binding energies of clusters forming crystalline
(fcc), decahedron and icosahedron structures are compared, showing that fcc
cuboctahedra are the most energetically favoured of these polyhedral model
structures. However, simulations of the freezing of liquid droplets produced a
characteristic form of ``shaved'' icosahedron, in which atoms are absent at the
edges and apexes of the polyhedron. This arrangement is energetically favoured
for 600-4000 atom clusters. Larger clusters favour crystalline structures.
Indeed, simulated freezing of a 6525-atom liquid droplet produced an imperfect
fcc Wulff particle, containing a number of parallel stacking faults. The
effects of temperature on the preferred structure of crystalline clusters below
the melting point have been considered. The implications of these results for
the interpretation of experimental data is discussed.Comment: 11 pages, 18 figues, new section added and one figure added, other
minor changes for publicatio
Transarterial chemoembolisation: effect of selectivity on tolerance, tumour response and survival
Aims To compare selective and non-selective TACE techniques in the treatment of HCC with a special emphasis on clinical and liver tolerance, tumour response and survival. Methods 184 patients with advanced HCC were retrospectively included. Three different TACE techniques were compared: non selective lipiodol-chemotherapy + non selective embolisation (TACE-technique group 1), non selective lipiodol-chemotherapy + selective embolisation (group 2), and selective lipiodol-chemotherapy + selective embolisation (group 3). Results In multivariate analysis TACE-technique group is an independently significant prognostic factor for poor clinical tolerance, poor liver tolerance and tumour response. The rate of patients with poor clinical tolerance was lower in group 3 (27.0%) than in groups 1 (64.1%, p < 10â3) or 2 (66.7%, p < 10â3). The rate of patients with poor liver tolerance was higher in group 2 (34.0%) than in groups 1 (17.6%, p = 0.050) or 3 (6.9%, p = 0.011). The rate of patients with tumour response was higher when embolisation was selective versus non-selective, i.e., group 2 + 3 (78.7%) versus group 1 (62.5%, p = 0.054). Overall survival was not significantly different between the three groups (p = 0.383). Conclusion Both selective techniques resulted in better tumour response. As for improving tolerance, our study suggests that the main technical factor is the use of selective lipiodol-chemotherapy injection
Localization Properties of the Periodic Random Anderson Model
We consider diagonal disordered one-dimensional Anderson models with an
underlying periodicity. We assume the simplest periodicity, i.e., we have
essentially two lattices, one that is composed of the random potentials and the
other of non-random potentials. Due to the periodicity special resonance
energies appear, which are related to the lattice constant of the non-random
lattice. Further on two different types of behaviors are observed at the
resonance energies. When a random site is surrounded by non-random sites, this
model exhibits extended states at the resonance energies, whereas otherwise all
states are localized with, however, an increase of the localization length at
these resonance energies. We study these resonance energies and evaluate the
localization length and the density of states around these energies.Comment: 4 page
A standardized procedure to obtain mesenchymal stem/stromal cells from minimally manipulated dental pulp and Whartonâs jelly samples
Transplantation of mesenchymal stem/stromal cells (MSCs) has emerged as an effective method to treat diseased or damaged organs and tissues, and hundreds of clinical trials using MSCs are currently under way to demonstrate the validity of such a therapeutic approach. However, most MSCs used for clinical trials are prepared in research laboratories with insufficient manufacturing quality control.In particular, laboratories lack standardized procedures for in vitro isolation of MSCs from tissue samples, resulting in heterogeneous populations of cells and variable experimental and clinical results. MSCs are now referred to as Human Cellular Tissue-based Products or Advanced Therapy Medicinal Products, and guidelines from the American Code of Federal Regulation of the Food and Drug Administration (21 CFR Part 1271) and from the European Medicines Agency (European Directive 1394/2007) define requirements for appropriate production of these cells. These guidelines, commonly called âGood Manufacturing Practicesâ (GMP), include recommendations about laboratory cell culture procedures to ensure optimal reproducibility, efficacy and safety of the final medicinal product. In particular, the Food and Drug Administration divides ex vivo cultured cells into âminimallyâ and âmore than minimallyâ manipulated samples, in function of the use or not of procedures âthat might alter the biological features of the cellsâ. Today, minimal manipulation conditions have not been defined for the collection and isolation of MSCs (Torre et al. 2015)(Ducret et al. 2015).Most if not all culture protocols that have been reported so far are unsatisfactory, because of the use of xeno- or allogeneic cell culture media, enzymatic treatment and long-term cell amplification that are known to alter the quality of MSCs. The aim of this study was to describe a standardized procedure for recovering MSCs with minimal handling from two promising sources, the dental pulp (DP) and the Whartonâs jelly (WJ) of the umbilical cord. The quality and homogeneity of the expanded cell populations were assessed by using flow cytometry with criteria that go beyond the International Society of Cellular Therapy (ISCT) guidelines for MSC characterization
Unbiased Global Optimization of Lennard-Jones Clusters for N <= 201 by Conformational Space Annealing Method
We apply the conformational space annealing (CSA) method to the Lennard-Jones
clusters and find all known lowest energy configurations up to 201 atoms,
without using extra information of the problem such as the structures of the
known global energy minima. In addition, the robustness of the algorithm with
respect to the randomness of initial conditions of the problem is demonstrated
by ten successful independent runs up to 183 atoms. Our results indicate that
the CSA method is a general and yet efficient global optimization algorithm
applicable to many systems.Comment: revtex, 4 pages, 2 figures. Physical Review Letters, in pres
Impact of splenic artery ligation after major hepatectomy on liver function, regeneration and viability
It was reported that prevention of acute portal overpressure in small-for-size livers by inflow modulation results in a better postoperative outcome. The aim is to investigate the impact of portal blood flow reduction by splenic artery ligation after major hepatectomy in a murine model. Forty-eight rats were subjected to an 85% hepatectomy or 85% hepatectomy and splenic artery ligation. Both groups were evaluated at 24, 48, 72 and 120 post-operative hours: liver function, regeneration and viability. All methods and experiments were carried out in accordance with Coimbra University guidelines. Splenic artery ligation produces viability increase after 24âh, induces a relative decrease in oxidative stress during the first 48âhours, allows antioxidant capacity increment after 24âh, which is reflected in a decrease of half-time normalized liver curve at 48âh and at 72âh and in an increase of mitotic index between 48âh and 72âh. Splenic artery ligation combined with 85% hepatectomy in a murine model, allows portal inflow modulation, promoting an increase in hepatocellular viability and regeneration, without impairing the function, probably by inducing a less marked elevation of oxidative stress at first 48âhours
Guidelines for Perioperative Care for Liver Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations.
BACKGROUND: Enhanced Recovery After Surgery (ERAS) is a multimodal pathway developed to overcome the deleterious effect of perioperative stress after major surgery. In colorectal surgery, ERAS pathways reduced perioperative morbidity, hospital stay and costs. Similar concept should be applied for liver surgery. This study presents the specific ERAS Society recommendations for liver surgery based on the best available evidence and on expert consensus.
METHODS: A systematic review was performed on ERAS for liver surgery by searching EMBASE and Medline. Five independent reviewers selected relevant articles. Quality of randomized trials was assessed according to the Jadad score and CONSORT statement. The level of evidence for each item was determined using the GRADE system. The Delphi method was used to validate the final recommendations.
RESULTS: A total of 157 full texts were screened. Thirty-seven articles were included in the systematic review, and 16 of the 23 standard ERAS items were studied specifically for liver surgery. Consensus was reached among experts after 3 rounds. Prophylactic nasogastric intubation and prophylactic abdominal drainage should be omitted. The use of postoperative oral laxatives and minimally invasive surgery results in a quicker bowel recovery and shorter hospital stay. Goal-directed fluid therapy with maintenance of a low intraoperative central venous pressure induces faster recovery. Early oral intake and mobilization are recommended. There is no evidence to prefer epidural to other types of analgesia.
CONCLUSIONS: The current ERAS recommendations were elaborated based on the best available evidence and endorsed by the Delphi method. Nevertheless, prospective studies need to confirm the clinical use of the suggested protocol
Entropic effects on the Size Evolution of Cluster Structure
We show that the vibrational entropy can play a crucial role in determining
the equilibrium structure of clusters by constructing structural phase diagrams
showing how the structure depends upon both size and temperature. These phase
diagrams are obtained for example rare gas and metal clusters.Comment: 5 pages, 3 figure
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Discovery of Unusual Minerals in Paleolithic Black Pigments from Lascaux (France) and Ekain (Spain)
Analyses of archaeological materials aim to rediscover the know-how of Prehistoric people by determining the nature of the painting matter, its preparation mode, and the geographic origin of its raw materials. This study deals with identification of manganese oxides in black pigments by micro-XANES (X-ray absorption near-edge structure) based on previous TEM (transmission electron microscopy) studies. Complex mixtures of the manganese oxides studied are present in some of mankind's oldest known paintings, namely those from the caves of Lascaux (Dordogne, France) and Ekain (Basque country, Spain). Scarce manganese oxide minerals, including groutite, hausmannite, and manganite, were found for the first time in Paleolithic art at these archaeological sites. Because there are no known deposits of such minerals in these areas, more distant origins and trade routes are inferred. The closest known Mn-rich geological province for Lascaux is the central Pyrenees, which is {approx} 250 km from the Dordogne area
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