3,235 research outputs found
A possible cosmological application of some thermodynamic properties of the black body radiation in dimensional Euclidean spaces
In this work we present the generalization of some thermodynamic properties
of the black body radiation (BBR) towards an dimensional Euclidean space.
For this case the Planck function and the Stefan-Boltzmann law have already
been given by Landsberg and de Vos and some adjustments by Menon and Agrawal.
However, since then no much more has been done on this subject and we believe
there are some relevant aspects yet to explore. In addition to the results
previously found we calculate the thermodynamic potentials, the efficiency of
the Carnot engine, the law for adiabatic processes and the heat capacity at
constant volume. There is a region at which an interesting behavior of the
thermodynamic potentials arise, maxima and minima appear for the BBR
system at very high temperatures and low dimensionality, suggesting a possible
application to cosmology. Finally we propose that an optimality criterion in a
thermodynamic framework could have to do with the nature of the universe.Comment: 9 pages, 8 figure
3D model evolution of a leak based on GPR image interpretations
This paper presents some aspects of the time propagation of underground water leakage in controlled laboratory conditions using a drilled polyvinyl chloride (PVC) pipe and interpreting ground penetrating radar (GPR) images. GPR pre-processed images are interpreted for easy identification and extraction of surfaces and volumes of water leakage. Finally, the temporal evolution of a water leak is shown using 3D models based on interpretation of GPR images. Water volumes obtained using this approach can be easily observed by personnel who lack highly specialized training in the analysis of raw data. The results of this study are promising and can help develop techniques to validate non-destructive models for the identification, distribution, and prediction of water leaks in water supply systems using GPR.Part of this work has been developed under the support of an FPI (Formacion de Personal Investigador)-UPV (Universitat Politecnica de Valencia) scholarship granted to the second author by the Programa de Ayudas de Investigacion y Desarrollo (PAID) of the Universitat Politecnica de Valencia, and the support of Fundacion Carolina PhD, within its short stances scholarship program for the first author. The use of English in this paper has been revised by John Rawlins.Ocana-Levario, S.; Ayala Cabrera, D.; Izquierdo Sebastián, J.; Pérez García, R. (2015). 3D model evolution of a leak based on GPR image interpretations. Water Science and Technology: Water Supply. 15(6):1312-1319. doi:10.2166/ws.2015.093S1312131915
Infrared spectroscopic identification of the C–O stretching vibration associated with the tyrosyl Z⋅ and D⋅ radicals in photosystem II2Supported by NIH GM 43272 (B.A.B.), NSF MCB 94-18164 (B.A.B.), a graduate minority supplement to NIH GM 43273 (I.A.), a graduate fellowship from Committee on Institutional Cooperation, University of Minnesota (I.A.), and a summer research fellowship from Dupont, Central Research and Development, administered through the University of Minnesota (E.T.G.).2
AbstractPhotosystem II (PSII) is a multisubunit complex, which catalyzes the photo-induced oxidation of water and reduction of plastoquinone. Difference Fourier-transform infrared (FT-IR) spectroscopy can be used to obtain information about the structural changes accompanying oxidation of the redox-active tyrosines, D and Z, in PSII. The focus of our work is the assignment of the 1478 cm−1 vibration, which is observable in difference infrared spectra associated with these tyrosyl radicals. The first set of FT-IR experiments is performed with continuous illumination. Use of cyanobacterial strains, in which isotopomers of tyrosine have been incorporated, supports the assignment of a positive 1478/1477 cm−1 mode to the C–O stretching vibration of the tyrosyl radicals. In negative controls, the intensity of this spectral feature decreases. The negative controls involve the use of inhibitors or site-directed mutants, in which the oxidation of Z or D is eliminated, respectively. The assignment of the 1478/1477 cm−1 vibrational mode is also based on control EPR and fluorescence measurements, which demonstrate that no detectable Fe2+QA− signal is generated under FT-IR experimental conditions. Additionally, the difference infrared spectrum, associated with formation of the S2QA− state, argues against the assignment of the positive 1478 cm−1 line to the C–O vibration of QA−. In the second set of FT-IR experiments, single turnover flashes are employed, and infrared difference spectra are recorded as a function of time after photoexcitation. Comparison to kinetic transients generated in control EPR experiments shows that the decay of the 1477 cm−1 line precisely parallels the decay of the D⋅ EPR signal. Taken together, these two experimental approaches strongly support the assignment of a component of the 1478/1477 cm−1 vibrational lines to the C–O stretching modes of tyrosyl radicals in PSII. Possible reasons for the apparently contradictory results of Hienerwadel et al. (Biochemistry 35 (1996) 15447–15460 and Biochemistry 36 (1997) 14705–14711) are discussed
A new species in the major malaria vector complex sheds light on reticulated species evolution
Complexes of closely related species provide key insights into the rapid and independent evolution of adaptive traits. Here, we described and studied Anopheles fontenillei sp.n., a new species in the Anopheles gambiae complex that we recently discovered in the forested areas of Gabon, Central Africa. Our analysis placed the new taxon in the phylogenetic tree of the An. gambiae complex, revealing important introgression events with other members of the complex. Particularly, we detected recent introgression, with Anopheles gambiae and Anopheles coluzzii, of genes directly involved in vectorial capacity. Moreover, genome analysis of the new species allowed us to clarify the evolutionary history of the 3La inversion. Overall, An. fontenillei sp.n. analysis improved our understanding of the relationship between species within the An. gambiae complex, and provided insight into the evolution of vectorial capacity traits that are relevant for the successful control of malaria in Africa
Pumped heat energy storage with liquid media: Thermodynamic assessment by a transcritical Rankine-like model
[EN]A pumped heat energy storage (PHES) system based on a Rankine cycle for supercritical working fluids, such
as carbon dioxide and ammonia, accounting for the irreversible latent and sensible heat transfers between
the working fluid and the storage liquid medium, as water or thermal oil, is analyzed. The model also
includes several parameters such as pressure losses, heat exchanger efficiencies, and isentropic efficiencies of
the compressor, pump, and expansion devices (such as turbines and valves), that take into account the main
internal and external losses and heat leak to the environment. The model allows for the calculation of specific
energy, the heat pump performance coefficient, heat engine efficiency, and overall round-trip efficiency, as well
as the temperatures of the working fluid and reservoirs. A zero-dimensional model is also used to determine
the time dependence of heat leak in the tanks. The main results show that this technology could achieve
round trip efficiency values in the order of 50–70%. Irreversibilities in compression and expansion appears
as the most influential energy losses factor. The time effect of the ambient conditions on the tanks has been
analyzed for a wet subtropical climate but it seems that the ambient conditions have no major influence on the
performance of the system. In addition, explicit numerical results and temperature–entropy plots are presented
for two representative systems as carbon dioxide-water and ammonia-thermal oil to take into account the main
values in an operating condition
Recommended from our members
The mechanical hybrid vehicle: an investigation of a flywheel-based vehicular regenerative energy capture system
Capturing braking energy by regeneration into an onboard energy storage unit offers the potential to reduce significantly the fuel consumption of vehicles. A common technique is to generate electricity in the motors of a hybrid electric vehicle when braking, and to use this to charge an onboard electrochemical battery. However, such batteries are costly, bulky, and generally not amenable to fast charging as this affects battery life and capacity. In order to overcome these problems, a mechanical energy storage system capable of accepting and delivering surges of power is proposed and investigated. A scale physical model of the system, based around a flywheel, a planetary gear set, and a brake, was built and operated in a laboratory. Tests showed that the proposed system could be used to store and provide braking energy between a flywheel and a vehicle, the latter emulated by an air-drag dynamometer. This validated the operating principle of the system and its computational model. Further, a computational analysis of a full-size vehicle incorporating the mechanical energy storage system was conducted. The results showed that the utilization of this system in a vehicle, when compared with a conventional vehicle, led to reductions in emissions and fuel consumption
Towards Minimal Barcodes
In the setting of persistent homology computation, a useful tool is the persistence barcode representation in which pairs of birth and death times of homology classes are encoded in the form of intervals. Starting from a polyhedral complex K (an object subdivided into cells which are polytopes) and an initial order of the set of vertices, we are concerned with the general problem of searching for filters (an order of the rest of the cells) that provide a minimal barcode representation in the sense of having minimal number of “k-significant” intervals, which correspond to homology classes with life-times longer than a fixed number k. As a first step, in this paper we provide an algorithm for computing such a filter for k = 1 on the Hasse diagram of the poset of faces of K
Incidence, in-hospital case-fatality rates, and management practices in Puerto Ricans hospitalized with acute myocardial infarction
OBJECTIVE: There are extremely limited data on minority populations, especially Hispanics, describing the clinical epidemiology of acute coronary disease. The aim of this study is to examine the incidence rate of acute myocardial infarction (AMI), in-hospital case-fatality rate (CFR), and management practices among residents of greater San Juan (Puerto Rico) who were hospitalized with an initial AMI.
METHODS: Our trained study staff reviewed and independently validated the medical records of patients who had been hospitalized with possible AMI at any of the twelve hospitals located in greater San Juan during calendar year 2007.
RESULTS: The incidence rate (# per 100,000 population) of 1,415 patients hospitalized with AMI increased with advancing age and were significantly higher for older patients for men (198) than they were for women (134). The average age of the study population was 64 years, and women comprised 45% of the study sample. Evidence-based cardiac therapies, e.g., aspirin, beta blockers, ACE inhibitors/angiotensin receptor blockers, and statins, were used with 60% of the hospitalized patients, and women were less likely than men to have received these therapies (59% vs. 65%) or to have undergone interventional cardiac procedures (47% vs. 59%) (p \u3c 0.05). The in-hospital CFR increased with advancing age and were higher for women (8.6%) than they were for men (6.0%) (p \u3c 0.05).
CONCLUSION: Efforts are needed to reduce the magnitude of AMI, enhance the use of evidence-based cardiac therapies, reduce possible gender disparities, and improve the short-term prognoses of Puerto Rican patients hospitalized with an initial AMI
Towards precision medicine: defining and characterizing adipose tissue dysfunction to identify early immunometabolic risk in symptom-free adults from the GEMM family study
Interactions between macrophages and adipocytes are early molecular factors influencing adipose tissue (AT) dysfunction, resulting in high leptin, low adiponectin circulating levels and low-grade metaflammation, leading to insulin resistance (IR) with increased cardiovascular risk. We report the characterization of AT dysfunction through measurements of the adiponectin/leptin ratio (ALR), the adipo-insulin resistance index (Adipo-IRi), fasting/postprandial (F/P) immunometabolic phenotyping and direct F/P differential gene expression in AT biopsies obtained from symptom-free adults from the GEMM family study. AT dysfunction was evaluated through associations of the ALR with F/P insulin-glucose axis, lipid-lipoprotein metabolism, and inflammatory markers. A relevant pattern of negative associations between decreased ALR and markers of systemic lowgrade metaflammation, HOMA, and postprandial cardiovascular risk hyperinsulinemic, triglyceride and GLP-1 curves was found. We also analysed their plasma non-coding microRNAs and shotgun lipidomics profiles finding trends that may reflect a pattern of adipose tissue dysfunction in the fed and fasted state. Direct gene differential expression data showed initial patterns of AT molecular signatures of key immunometabolic genes involved in AT expansion, angiogenic remodelling and immune cell migration. These data reinforce the central, early role of AT dysfunction at the molecular and systemic level in the pathogenesis of IR and immunometabolic disorders
Antimicrobial and antioxidant properties of byproduct extracts of mango fruit
Byproducts of fruit processing could have higher content of phenolic compounds that can act as antimicrobial and antioxidant agents. In this context, the main objective of this study was to obtain extracts from peel, seed, and unused flesh of Haden, Ataulfo and Tommy Atkins mango varieties, in order to measure their antioxidant and antimicrobial properties. The extraction was performed using different methods, such as methanolic-polar, methanolic-non-polar, ethanolic-polar, ethanolic-non-polar and water infusion. The total phenolic content of the ethanolic-non-polar extract from seed of mango Haden showed 875.06 mg/g, DPPH EC50: 0.04 mg/mL, cau-sing a 100 % inhibition of bacteria pathogens applying 25 mg/mL and inhibition of 89.78 % against Alternaria applying 6.25 mg/mL. The flesh always showed the lowest content and bioactivity of the tested parameters. These results demonstrate the antimicrobial and antioxidant potential uses of fruit byproducts as sources of bioactive compounds
- …