957 resultados para Non ideal dynamic system
Resumo:
The single electron transistor (SET) is a charge-based device that may complement the dominant metal-oxide-semiconductor field effect transistor (MOSFET) technology. As the cost of scaling MOSFET to smaller dimensions are rising and the the basic functionality of MOSFET is encountering numerous challenges at dimensions smaller than 10nm, the SET has shown the potential to become the next generation device which operates based on the tunneling of electrons. Since the electron transfer mechanism of a SET device is based on the non-dissipative electron tunneling effect, the power consumption of a SET device is extremely low, estimated to be on the order of 10^-18J. The objectives of this research are to demonstrate technologies that would enable the mass produce of SET devices that are operational at room temperature and to integrate these devices on top of an active complementary-MOSFET (CMOS) substrate. To achieve these goals, two fabrication techniques are considered in this work. The Focus Ion Beam (FIB) technique is used to fabricate the islands and the tunnel junctions of the SET device. A Ultra-Violet (UV) light based Nano-Imprint Lithography (NIL) call Step-and-Flash- Imprint Lithography (SFIL) is used to fabricate the interconnections of the SET devices. Combining these two techniques, a full array of SET devices are fabricated on a planar substrate. Test and characterization of the SET devices has shown consistent Coulomb blockade effect, an important single electron characteristic. To realize a room temperature operational SET device that function as a logic device to work along CMOS, it is important to know the device behavior at different temperatures. Based on the theory developed for a single island SET device, a thermal analysis is carried out on the multi-island SET device and the observation of changes in Coulomb blockade effect is presented. The results show that the multi-island SET device operation highly depends on temperature. The important parameters that determine the SET operation is the effective capacitance Ceff and tunneling resistance Rt . These two parameters lead to the tunneling rate of an electron in the SET device, Γ. To obtain an accurate model for SET operation, the effects of the deviation in dimensions, the trap states in the insulation, and the background charge effect have to be taken into consideration. The theoretical and experimental evidence for these non-ideal effects are presented in this work.
Resumo:
The purpose of this study was to investigate variations in hepatic regulation of metabolism during the dry period, after parturition, and in early lactation in dairy cows. For this evaluation, cows were divided into 2 groups based on the plasma concentration of beta-hydroxybutyric acid (BHBA) in wk 4 postpartum (PP; group HB, BHBA >0.75 mmol/L; group LB, BHBA <0.75 mmol/L, respectively). Liver biopsies were obtained from 28 cows at drying off (mean 59 +/- 8 d antepartum), on d 1, and in wk 4 and 14 PP. Blood samples were collected every 2 wk during this entire period. Liver samples were analyzed for mRNA abundance of genes related to carbohydrate metabolism (pyruvate carboxylase, PC; phosphoenolpyruvate carboxykinase, PEPCK; citrate synthase, CS), fatty acid biosynthesis (ATP citrate lyase, ACLY) and oxidation (acyl-CoA synthetase long-chain, ACSL; carnitine palmitoyltransferase 1A, CPT 1A; carnitine palmitoyltransferase 2, CPT 2; acyl-coenzyme A dehydrogenase very long chain, ACADVL), cholesterol biosynthesis (3-hydroxy-3-methylglutaryl-coenzyme A synthase 1, HMGCS1), ketogenesis (3-hydroxy-3-methylglutaryl-coenzyme A synthase 2, HMGCS2), and of genes encoding the transcription factors peroxisome proliferator-activated receptor alpha (PPARalpha), peroxisome proliferator-activated receptor gamma (PPARgamma), and sterol regulatory element binding factor 1 (SREBF1). Blood plasma was assayed for concentrations of glucose, BHBA, nonesterified fatty acids, cholesterol, triglycerides, insulin, insulin-like growth factor-I, and thyroid hormones. In both groups, plasma parameters followed a pattern usually observed in dairy cows. However, changes were moderate and the energy balance in cows turned positive in wk 7 PP for both groups. Additionally, the energy balance and milk yield were similar for both groups after parturition onwards. Significant group effects were found at drying off, when plasma concentrations of triglycerides were higher in LB than in HB, and in wk 4 PP, when plasma concentrations of glucose and IGF-I were lower in HB than in LB. Similarly, moderate changes in mRNA expression of hepatic genes between the different time points were observed, although HB cows showed more adaptive performance than LB cows based on changes in mRNA expression of PEPCKc, PEPCKm, CS, CPT 1A, CPT 2, and PPARalpha. Part of the variation measured in this study was explained by parity. Significant Spearman rank correlation coefficients between the variables were not similar at each time point and were not similar between the groups at each time point, suggesting that metabolic regulation differs between cows. In conclusion, metabolic regulation in dairy cows is a dynamic system, and differs obviously between cows at different metabolic stages related to parturition.
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Hydrodynamics can be consistently formulated on surfaces of arbitrary co-dimension in a background space-time, providing the effective theory describing long-wavelength perturbations of black branes. When the co-dimension is non-zero, the system acquires fluid-elastic properties and constitutes what is called a fluid brane. Applying an effective action approach, the most general form of the free energy quadratic in the extrinsic curvature and extrinsic twist potential of stationary fluid brane configurations is constructed to second order in a derivative expansion. This construction generalizes the Helfrich-Canham bending energy for fluid membranes studied in theoretical biology to the case in which the fluid is rotating. It is found that stationary fluid brane configurations are characterized by a set of 3 elastic response coefficients, 3 hydrodynamic response coefficients and 1 spin response coefficient for co-dimension greater than one. Moreover, the elastic degrees of freedom present in the system are coupled to the hydrodynamic degrees of freedom. For co-dimension-1 surfaces we find a 8 independent parameter family of stationary fluid branes. It is further shown that elastic and spin corrections to (non)-extremal brane effective actions can be accounted for by a multipole expansion of the stress-energy tensor, therefore establishing a relation between the different formalisms of Carter, Capovilla-Guven and Vasilic-Vojinovic and between gravity and the effective description of stationary fluid branes. Finally, it is shown that the Young modulus found in the literature for black branes falls into the class predicted by this approach - a relation which is then used to make a proposal for the second order effective action of stationary blackfolds and to find the corrected horizon angular velocity of thin black rings.
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With its invariant cell lineage, easy genetics and small genome, the nematode Caenorhabditis elegans has emerged as one of the prime models in developmental biology over the last 50 years. Surprisingly however, until a decade ago very little was known about nuclear organization in worms, even though it is an ideal model system to explore the link between nuclear organization and cell fate determination. Here, we review the latest findings that exploit the repertoire of genetic tools developed in worms, leading to the identification of important sequences and signals governing the changes in chromatin tridimensional architecture. We also highlight parallels and differences to other model systems.
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BACKGROUND: Whole-body hypothermia reduced the frequency of death or moderate/severe disabilities in neonates with hypoxic-ischemic encephalopathy in a randomized, controlled multicenter trial. OBJECTIVE: Our goal was to evaluate outcomes of safety and effectiveness of hypothermia in infants up to 18 to 22 months of age. DESIGN/METHODS: A priori outcomes were evaluated between hypothermia (n = 102) and control (n = 106) groups. RESULTS: Encephalopathy attributable to causes other than hypoxia-ischemia at birth was not noted. Inotropic support (hypothermia, 59% of infants; control, 56% of infants) was similar during the 72-hour study intervention period in both groups. Need for blood transfusions (hypothermia, 24%; control, 24%), platelet transfusions (hypothermia, 20%; control, 12%), and volume expanders (hypothermia, 54%; control, 49%) was similar in the 2 groups. Among infants with persistent pulmonary hypertension (hypothermia, 25%; control, 22%), nitric-oxide use (hypothermia, 68%; control, 57%) and placement on extracorporeal membrane oxygenation (hypothermia, 4%; control, 9%) was similar between the 2 groups. Non-central nervous system organ dysfunctions occurred with similar frequency in the hypothermia (74%) and control (73%) groups. Rehospitalization occurred among 27% of the infants in the hypothermia group and 42% of infants in the control group. At 18 months, the hypothermia group had 24 deaths, 19 severe disabilities, and 2 moderate disabilities, whereas the control group had 38 deaths, 25 severe disabilities, and 1 moderate disability. Growth parameters were similar between survivors. No adverse outcomes were noted among infants receiving hypothermia with transient reduction of temperature below a target of 33.5 degrees C at initiation of cooling. There was a trend in reduction of frequency of all outcomes in the hypothermia group compared with the control group in both moderate and severe encephalopathy categories. CONCLUSIONS: Although not powered to test these secondary outcomes, whole-body hypothermia in infants with encephalopathy was safe and was associated with a consistent trend for decreasing frequency of each of the components of disability.
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The paleoglaciological concept that during the Pleistocene glacial hemi-cycles a super-large, structurally complex ice sheet developed in the Arctic and behaved as a single dynamic system, as the Antarctic ice sheet does today, has not yet been subjected to concerted studies designed to test the predictions of this concept. Yet, it may hold the keys to solutions of major problems of paleoglaciology, to understanding climate and sea-level changes. The Russian Arctic is the least-known region exposed to paleoglaciation by a hypothetical Arctic ice sheet but now it is more open to testing the concept. Implementation of these tests is a challenging task, as the region is extensive and the available data are controversial. Well-planned and coordinated field projects are needed today, as well as broad discussion of the known evidence, existing interpretations and new field results. Here we present the known evidence for paleoglaciation of the Russian Arctic continental shelf and reconstruct possible marine ice sheets that could have produced that evidence.
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Earth-orbiting satellites can now monitor calving of large icebergs from ice shelves bordering the marine West Antarctic Ice Sheet, and recent calving events have stimulated interest in calving mechanisms. To advance this interest pioneering work in brittle and ductile fracture mechanics is reviewed, leading to a new application to calving of giant icebergs from Antarctic ice shelves. The aim is to view iceberg calving as more than terminal events for Antarctic ice when glaciologists lose interest. Instead calving launches Antarctic ice into the larger dynamic system of Earth's climate machine. This encourages a holistic approach to glaciology.
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Aim: The landscape metaphor allows viewing corrective experiences (CE) as pathway to a state with relatively lower 'tension' (local minimum). However, such local minima are not easily accessible but obstructed by states with relatively high tension (local maxima) according to the landscape metaphor (Caspar & Berger, 2012). For example, an individual with spider phobia has to transiently tolerate high levels of tension during an exposure therapy to access the local minimum of habituation. To allow for more specific therapeutic guidelines and empirically testable hypotheses, we advance the landscape metaphor to a scientific model which bases on motivational processes. Specifically, we conceptualize CEs as available but unusual trajectories (=pathways) through a motivational space. The dimensions of the motivational state are set up by basic motives such as need for agency or attachment. Methods: Dynamic system theory is used to model motivational states and trajectories using mathematical equations. Fortunately, these equations have easy-to-comprehend and intuitive visual representations similar to the landscape metaphor. Thus, trajectories that represent CEs are informative and action guiding for both therapists and patients without knowledge on dynamic systems. However, the mathematical underpinnings of the model allow researchers to deduct hypotheses for empirical testing. Results: First, the results of simulations of CEs during exposure therapy in anxiety disorders are presented and compared to empirical findings. Second, hypothetical CEs in an autonomy-attachment conflict are reported from a simulation study. Discussion: Preliminary clinical implications for the evocation of CEs are drawn after a critical discussion of the proposed model.
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Drugs targeting the immune system such as corticosteroids, antihistamines and immunosuppressants have been widely exploited in the treatment of inflammatory, allergic and autoimmune disorders during the second half of the 20th century. The recent advances in immunopharmacological research have made available new classes of clinically relevant drugs. These comprise protein kinase inhibitors and biologics, such as monoclonal antibodies, that selectively modulate the immune response not only in cancer and autoimmunity but also in a number of other human pathologies. Likewise, more effective vaccines utilizing novel antigens and adjuvants are valuable tools for the prevention of transmissible infectious diseases and for allergen-specific immunotherapy. Consequently, immunopharmacology is presently considered as one of the expanding fields of pharmacology. Immunopharmacology addresses the selective regulation of immune responses and aims to uncover and exploit beneficial therapeutic options for typical and non-typical immune system-driven unmet clinical needs. While in the near future a number of new agents will be introduced, improving the effectiveness and safety of those currently in use is imperative for all researchers and clinicians working in the fields of immunology, pharmacology and drug discovery. The newly formed ImmuPhar (http://iuphar.us/index.php/sections-subcoms/immunopharmacology) is the Immunopharmacology Section of the International Union of Basic and Clinical Pharmacology (IUPHAR, http://iuphar.us/). ImmuPhar provides a unique international expert-lead platform that aims to dissect and promote the growing understanding of immune (patho)physiology. Moreover, it challenges the identification and validation of drug targets and lead candidates for the treatment of many forms of debilitating disorders, including, among others, cancer, allergies, autoimmune and metabolic diseases.
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The baker's yeast, Saccharomyces cerevisiae responds to the cytotoxic effects of elevated temperature (37-42°C) by activating transcription of ∼150 genes, termed heat shock genes, collectively required to compensate for the abundance of misfolded and aggregated proteins and various physiological modifications necessary for the cell to survive and grow at heat shock temperatures. An intriguing facet of the yeast heat shock response is the remarkable similarity it shares with the global remodeling that occurs in mammalian cells in response to numerous pathophysiological conditions including cancer and cardiovascular disease and thus provides an ideal model system. I have therefore investigated several novel features of stress signaling, transcriptional regulation, and physiology. Initial work focused on the characterization of SYM1, a novel heat shock gene in yeast which was demonstrated to be required for growth on the nonfermentable carbon source ethanol at elevated temperature, and to be the functional ortholog of the mammalian kidney disease gene, Mpv17. Additional work addressed the role of two proteins, the Akt-related kinase, Sch9, and Sse1, the yeast Hsp110 protein chaperone homolog, in signaling by protein kinase A, establishing Sse1 as a critical negative regulator of this pathway. Furthermore, I have demonstrated a role for Sse1 in biogenesis and stability of the stress-response transcription factor, Msn2; a finding that has been extended to include a select subset of additional high molecular weight proteins, suggesting a more global role for this chaperone in stabilizing the cellular proteome. The final emphasis of my doctoral work has included the finding that celastrol, a compound isolated from the plant family Celasfraceae, a component of traditional Chinese herbal medicine, can activate heat shock transcription factor (Hsf1) in yeast and mammalian cells through an oxidative stress mechanism. Celastrol treatment simultaneously activates both heat shock and oxidative stress response pathways, resulting in increased cytoprotection. ^
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Membranes are essential for the integrity and function of the cell. The collective property of the lipid bilayer is critical in providing an optimal functioning environment for membrane proteins. The simple yet well-characterized bacterium Escherichia coli serves an ideal model system to study the function of specific lipids since its lipid content can be easily manipulated. The most abundant lipid in E. coli membrane is phosphatidylethanolamine (PE, 70-80%). A PE-lacking E. coli mutant displays a complex mixture of deficient phenotypes, suggesting a profound role for PE in different aspects of cell function. A novel role of PE as a topological and functional determinant for membrane proteins has been established using lactose permease (LacY) as a model protein. PE is found to be required for energy-dependent uphill transport process of LacY. In PE-lacking membranes, LacY undergoes a dramatic conformational change, and the first half of the protein adopts an inverted topology with respect to the bilayer plane. ^ The work reported here was initiated to understand the molecular properties of lipids that enable their function as topological and functional determinants for membrane proteins. A glycolipid, monoglucosyldiacylglycerol (MGlcDAG) which shares physicochemical similarities with PE, was introduced to PE-lacking E. coli membranes. The introduction of MGlcDAG suppresses many of the PE-deficient phenotypes, and in particular supports the function and native topology of LacY. ^ The lipid-sensitive topogenic signals encoded in the amino acid sequence of LacY were also identified. Native LacY adopts an inverted topology when synthesized without PE, but mutation of specific acidic residues in the cytoplasmic extra-membrane domains can prevent this inversion and supports a native topological organization of LacY in PE-lacking membranes. These results suggest that it is the interplay between the collective charge properties of the lipid bilayer and extra-membrane loops of protein that determines the final orientation of transmembrane domains. By comparing the similarities as well as differences between these two lipids, we established how specific physical and chemical properties of lipids influence various cell functions and elucidated the molecular basis for the novel role of lipids in determining membrane protein topology. ^
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Globalization has resulted in unprecedented movements of people, goods, and alien species across the planet. Although the impacts of biological invasions are widely appreciated, a bias exists in research effort to post-dispersal processes because of the difficulties of measuring propagule pressure. The Antarctic provides an ideal model system in which to investigate propagule movements because of the region's isolation and small number of entry routes. Here we investigated the logistics operations of the South African National Antarctic Programme (SANAP) and quantified the initial dispersal of alien species into the region. we found that over 1400 seeds from 99 taxa are transported into the Antarctic each field season in association with SANAP passenger luggage and cargo. The first ever assessment of propagule drop-off indicated that 30-50% of these propagules will enter the recipient environment. Many of the taxa include cosmopolitan weeds and known aliens in the Antarctic, indicating that logistics operations form part of a globally self-perpetuating cycle moving alien species between areas of human disturbance. in addition, propagules of some taxa native to the Antarctic region were also found, suggesting that human movements may be facilitating intra-regional homogenization. Several relatively simple changes in biosecurity policy that could significantly reduce the threat of introduction of nonnative species are suggested.
Resumo:
A partir de la aceptación de la biblioteca como parte del ciclo de creación, organización y diseminación del conocimiento cambió el concepto de la misma de una entidad cerrada hacia un sistema dinámico en constante interacción con su entorno. Así se la reconoció como una institución social más que como una colección de documentos. Desde entonces se percibió a la biblioteca como una entidad en la que se podía aplicar los principios de gestión. Desde entonces se utilizaron distintas herramientas de gestión para la toma de decisiones en el ámbito de las bibliotecas. Entre estas herramientas son de gran importancia en el control estadístico de procesos los gráficos de control, utilizados para medir la estabilidad de un proceso a través del tiempo. Han tenido amplia aplicación en el control estadístico de la calidad, comenzando en el ámbito industrial. Hoy su aplicación se ha extendido a una gran variedad de disciplinas incluyen empresas de servicios y unidades administrativas. Aquí se presentan a los gráficos de control como una importante herramienta de gestión aplicada a los procesos técnicos permitiendo su evaluación y el monitoreo de su desempeño a partir de la utilización de indicadores y otros datos de carácter diagnóstico
Resumo:
A partir de la aceptación de la biblioteca como parte del ciclo de creación, organización y diseminación del conocimiento cambió el concepto de la misma de una entidad cerrada hacia un sistema dinámico en constante interacción con su entorno. Así se la reconoció como una institución social más que como una colección de documentos. Desde entonces se percibió a la biblioteca como una entidad en la que se podía aplicar los principios de gestión. Desde entonces se utilizaron distintas herramientas de gestión para la toma de decisiones en el ámbito de las bibliotecas. Entre estas herramientas son de gran importancia en el control estadístico de procesos los gráficos de control, utilizados para medir la estabilidad de un proceso a través del tiempo. Han tenido amplia aplicación en el control estadístico de la calidad, comenzando en el ámbito industrial. Hoy su aplicación se ha extendido a una gran variedad de disciplinas incluyen empresas de servicios y unidades administrativas. Aquí se presentan a los gráficos de control como una importante herramienta de gestión aplicada a los procesos técnicos permitiendo su evaluación y el monitoreo de su desempeño a partir de la utilización de indicadores y otros datos de carácter diagnóstico
Resumo:
A partir de la aceptación de la biblioteca como parte del ciclo de creación, organización y diseminación del conocimiento cambió el concepto de la misma de una entidad cerrada hacia un sistema dinámico en constante interacción con su entorno. Así se la reconoció como una institución social más que como una colección de documentos. Desde entonces se percibió a la biblioteca como una entidad en la que se podía aplicar los principios de gestión. Desde entonces se utilizaron distintas herramientas de gestión para la toma de decisiones en el ámbito de las bibliotecas. Entre estas herramientas son de gran importancia en el control estadístico de procesos los gráficos de control, utilizados para medir la estabilidad de un proceso a través del tiempo. Han tenido amplia aplicación en el control estadístico de la calidad, comenzando en el ámbito industrial. Hoy su aplicación se ha extendido a una gran variedad de disciplinas incluyen empresas de servicios y unidades administrativas. Aquí se presentan a los gráficos de control como una importante herramienta de gestión aplicada a los procesos técnicos permitiendo su evaluación y el monitoreo de su desempeño a partir de la utilización de indicadores y otros datos de carácter diagnóstico