102,135 research outputs found
Efficient excitation-transfer across fully connected networks via local-energy optimization
Full text linkWe study the excitation transfer across a fully connected quantum network
whose sites energies can be artificially designed. Starting from a simplified
model of a broadly-studied physical system, we systematically optimize its
local energies to achieve high excitation transfer for various environmental
conditions, using an adaptive Gradient Descent technique and Automatic
Differentiation. We show that almost perfect transfer can be achieved with and
without local dephasing, provided that the dephasing rates are not too large.
We investigate our solutions in terms of resilience against variations in
either the network connection strengths, or size, as well as coherence losses.
We highlight the different features of a dephasing-free and dephasing-driven
transfer. Our work gives further insight into the interplay between coherence
and dephasing effects in excitation-transfer phenomena across fully connected
quantum networks. In turn, this will help designing optimal transfer in
artificial open networks through the simple manipulation of local energies.Comment: 11 pages, 8 figure
The Hemopoietic progenitor 32DCl3 (G) cells synthesize C3 molecules upon differentiation or neoplastic transformation
No full text32DCl3(G) cells are a diploid, nontumorigenic, IL-3-dependent hemopoietic progenitor cell line, which undergoes terminal differentiation into neutrophilic granulocytes when cultured in presence of G-CSF. The infection with BALB-Moloney murine sarcoma virus, containing a v-HA-ras oncogene, renders this cell line IL-3 independent and continuously growing in the presence of G-CSF, nontumorigenic and with an apparent block at the level of promyelocyte/myelocyte (32D-Ha-ras). After infection with Abelson murine leukemia virus containing a v-abl oncogene, the cell line originates (32D-abl) that is also IL-3 independent but is tumorigenic and unable to differentiate in the presence of G-CSF. This cellular model allowed us to study the relationship between distinct steps of cell differentiation, neoplastic transformation, and C3 synthesis, activation, and characteristics of binding. We demonstrated that C3 synthesis, release, and cleavage are properties already present in the progenitor 32DCl3(G) cells. The more differentiated 32D-Ha-ras cells acquired C3 acceptor sites, apparently completely saturated by the constitutively released molecules. The transformation with Abelson murine leukemia virus, although it did not affect all these properties, let the cells bind considerable amounts of C3-related fragments activated in normal murine serum through the alternative pathway. This last event was a result of the acquisition of PMSF-sensitive serine proteases associated with the plasma membrane
Assessing the role of initial correlations in the entropy production rate for nonequilibrium harmonic dynamics
No full textEntropy production provides a general way to state the second law of thermodynamics for nonequilibrium scenarios. In open quantum system dynamics, it also serves as a useful quantifier of the degree of irreversibility. In this work we shed light on the relation between correlations, initial preparation of the system, and non-Markovianity by studying a system of two harmonic oscillators independently interacting with their local baths. Their dynamics, described by a time-local master equation, is solved to show, both numerically and analytically, that the global purity of the initial state of the system influences the behavior of the entropy production rate and that the latter depends algebraically on the entanglement that characterizes the initial state
Lymph node-derived lymphatic endothelial cells express functional costimulatory molecules and impair dendritic cell-induced allogenic T-cell proliferation.
No full textLymphatic endothelial cells (LECs) interact with different immune cells, including T cells within lymph nodes (LNs). However, direct interactions of LECs with immune cells have yet to be investigated. In vitro studies were performed to characterize primary cultures of human LECs derived from LNs in their capacity of interacting with T cells. The results show that LECs express HLA molecules and functional costimulatory molecules needed for T-cell activation. A direct binding of LECs and T cells was detected in cell cultures connected with a clustering of costimulatory molecules on the contact phase. LECs were also able to take up and process antigens. However, major histocompatibility complex class II(+) LECs fail to induce allogeneic T-cell proliferation. Interestingly, supernatants of IFN-γ activated LECs impair proliferation of T cells cocultured with allogeneic dendritic cells, suggesting an inhibitory role of LECs. Indoleamine 2,3 dioxygenase was identified as one inhibitory molecule, which may be responsible for the impaired CD4(+) T-cell proliferation. Our observations suggest a regulatory function for activated LECs on CD4(+) T cells, which may play a role in vivo in the maintenance of the critical balance between tolerance and recall responses.-Nörder, M., Gutierrez, M. G., Zicari, S., Cervi, E., Caruso, A., Guzmán, C. A. Lymph node-derived lymphatic endothelial cells express functional costimulatory molecules and impair dendritic cell-induced allogenic T-cell proliferation
Effects of glucocorticoids and progesterone on prostaglandin E2 and leukotriene B4 release by human fetal membranes at term gestation
No full textThe present study was undertaken to evaluate the effects of the glucocorticoid hormones betamethasone and hydrocortisone, and of progesterone on the relative production of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) by explants of human fetal membranes at term gestation in the absence of labor. Tissues (n = 7) were incubated either in the presence or in the absence of the above mentioned hormones. PGE2 and LTB4 were measured in culture medium by radioimmunoassays. Glucocorticoids and progesterone did not affect PGE2 output by tissues; however, they greatly stimulated LTB4 production. Moreover, both betamethasone and hydrocortisone significantly increased the ratio of LTB4 to PGE2 formation by tissues. These results suggest that glucocorticoid hormones and progesterone might influence arachidonic acid metabolism in human fetal membranes by stimulating the production of lipoxygenase rather than cyclooxygenase substances before the onset of labor
A reinforcement learning approach to the design of quantum chains for optimal energy and state transfer
Full text linkWe propose a bottom–up approach, based on reinforcement learning, to the design of a chain achieving efficient excitation-transfer performances. We assume distance-dependent interactions among particles arranged in a chain under tight-binding conditions. Starting from two particles and a localised excitation, we gradually increase the number of constitutents of the system so as to improve the transfer probability. We formulate the problem of finding the optimal locations and numbers of particles as a Markov decision process: we use proximal policy optimization to find the optimal chain-building policies and the optimal chain configurations under different scenarios. We consider both the case in which the target is a sink connected to the end of the chain and the case in which the target is the right-most particle in the chain. We address the problem of disorder in the chain induced by particle positioning errors. We apply our methodology to a simplified model of a relevant physical platform, consisting of trapped ions. We are able to achieve extremely high excitation transfer in all cases, with different chain configurations and properties depending on the specific conditions
Gastro-entero-pancreatic hormones in amniotic fluid from normal and diabetic pregnant women.
No full textClinical applications of analyses of hormones in amniotic fluid (AF) have recently been increased. In diabetic pregnancy, determinations of insulin and C-peptide in AF have been suggested as good indicators of the status of the foetus. We have investigated the pancreatic alpha and beta cell function by measuring insulin (IRI), C-peptide (CPR), glucagon (IRG), somatostatin (SLI), and gastric inhibitory polypeptide (GIP) in amniotic fluid collected during basal conditions or 2 h after an arginine test in 92 diabetic and 32 non-diabetic pregnant women. During basal conditions, in diabetic pregnant women, IRI, CPR and the insulin: glucagon molar ratio (I/G) were all significantly higher while amniotic fluid-IRG was significantly lower than in the controls. After arginine stimulation, IRI increased in AF of the diabetic pregnant women but not in AF of the controls while no differences were observed in AF-GIP and AF-SLI concentrations. Higher IRI and CPR, as well as lower IRG values were significantly related to poor maternal metabolic control. The occurrence of neonatal morbidity including macrosomia was significantly associated with increased AF, IRI and CPR concentrations after an arginine challenge and these factors were the most sensitive predictors of neonatal morbidity in infants of diabetic mothers. Increased AF glucose concentrations and I/G ratios were related to neonatal hypoglycaemia; jaundice and respiratory distress syndrome were associated to low concentrations of SF-IRG
Linked activation of nitric oxide synthase and cyclooxygenase in peripheral monocytes of asymptomatic migraine without aura patients
No full textMany reports indicate that nitric oxide (NO) could be involved in migraine without aura (MWA), an extremely diffuse clinical event. Since monocyte may be a relevant source of NO, we analysed monocyte activation in MWA patients, in a period in which they were free of symptoms. NO basal production by MWA peripheral monocytes was significantly higher than in healthy subjects (91.25+/-8.6 mu M/10 degrees cells vs. 22.6+/-3.2 mu M /10(6) cells). Interestingly, even the release of prostaglandin E-2 (PGE(2)), was higher in MWA patients than in healthy subjects (3137+/-320 pg/10 degrees cells vs. 1531+/-220 pg/10(6) cells). The incubation of monocytes from healthy subjects and MWA patients with N-nitro-L-arginine methyl ester caused a marked decrease of both NO and PGE(2) release. We hypothesise that NOS and cyclooxygenase pathways in monocytes are linked and are, in MWA patients, up-regulated, even in a symptoms-free period. NO and PGE(2) hyperproduction could therefore be involved in the neurovascular modifications leading to migraine attacks
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