3,186 research outputs found
Una aproximación práctica para el diseño de un proceso de reciclado de polímeros mediante disolución
La cantidad de residuos plásticos producidos en los últimos años se ha visto incrementada debido a la variedad de usos y las buenas propiedades que estos presentan. Por este motivo, es necesario ofrecer soluciones que permitan un reciclaje adecuado a cada tipo de residuo, siguiendo con las normativas vigentes. Entre las alternativas desarrolladas se encuentran el reciclado mecánico, químico y la incineración, sin embargo, estos metodos cuentan con determinados inconvenientes que dificultan su aplicación. Para solventar estos, se propone el tratamiento de los residuos mediante disolución, lo que implica la seleccion adecuada del mejor disolvente, con el objetivo de tratar la máxima cantidad de plástico posible. Esta selección se desarrolla siguiendo una serie de modelos teóricos que permiten el cálculo del parametro de solubilidad (d), y su interpretación a traves de distintos metodos gráficos que permiten seleccionar de manera sencilla los disolventes más adecuados. Por último, tambíen se muestran estrategias de cálculo para conocer las condiciones de operación que vienen definidas por una concentración y temperatura críticas, que limitan la región en la que la disolución permanece estable, y por tanto, es posible realizar el proceso de reciclado
Quantum Interference in Single Molecule Electronic Systems
We present a general analytical formula and an ab initio study of quantum
interference in multi-branch molecules. Ab initio calculations are used to
investigate quantum interference in a benzene-1,2-dithiolate (BDT) molecule
sandwiched between gold electrodes and through oligoynes of various lengths. We
show that when a point charge is located in the plane of a BDT molecule and its
position varied, the electrical conductance exhibits a clear interference
effect, whereas when the charge approaches a BDT molecule along a line normal
to the plane of the molecule and passing through the centre of the phenyl ring,
interference effects are negligible. In the case of olygoynes, quantum
interference leads to the appearance of a critical energy , at which the
electron transmission coefficient of chains with even or odd numbers of
atoms is independent of length. To illustrate the underlying physics, we derive
a general analytical formula for electron transport through multi-branch
structures and demonstrate the versatility of the formula by comparing it with
the above ab-initio simulations. We also employ the analytical formula to
investigate the current inside the molecule and demonstrate that large counter
currents can occur within a ring-like molecule such as BDT, when the point
charge is located in the plane of the molecule. The formula can be used to
describe quantum interference and Fano resonances in structures with branches
containing arbitrary elastic scattering regions connected to nodal sites.Comment: 12 pages, 11 figure
Drag reduction on a blunt body by self-adaption of rear flexibly hinged flaps
We study the aerodynamics of a blunt-based body with rear flexibly-hinged rigid flaps,
subject to a turbulent flow of Reynolds number Re = 12000, under aligned and cross
flow conditions with yaw angle β = 0◦ and β = 4◦. To that aim, different values of
the equivalent torsional stiffness are considered, to cover the range of reduced velocity
U∗ = (0, 3.48] in water tank experiments. The effect of the angular deflection of
plates on the drag and near wake flow is analyzed, experimentally and numerically.
The results show that, in the range of U∗ herein considered, the plates undergo an
inwards quasi-static, self-adaptive deflection, which is symmetric for yaw angles β = 0◦
and asymmetric for β = 4◦. In particular, the plates feature small mean deformation
angles for values of U∗ < 1, whereas a sharp and monotonic increase of such deflection
occurs for U∗ > 1, i.e. for lower values of the hinge’s stiffness, with an asymptotic
trend towards the larger values of U∗. A critical value of reduced velocity of U∗ ≃ 0.96
is obtained as the instability threshold above which plates depart from their initial
equilibrium position. The progressive streamlining of the trailing edge translates into
significant reductions of the associated mean drag coefficients. Thus, reductions close
to 19% with respect to reference static plates configurations are obtained for the most
flexible case of U∗ = 3.48 for both β = 0◦ and β = 4◦. A close inspection of the
near wake reveals that the inwards progressive mean displacement of the plates yields
a reduction in the recirculation bubble size. A symmetric evolution of the recirculating
bubble is observed for β = 0◦, whereas the bubble becomes asymmetric for β = 4◦,
with a larger leeward clockwise vortex. In both cases, the drag coefficient is shown
to vary linearly with the global aspect ratio of the recirculating bubble. The analysis
of the numerical results shows that the reduced extension of the recirculating bubble
significantly alters the formation length and intensity of the eddies size and associated
pressure. It is observed that despite the local pressure decrease in the vortices shed from
the trailing edges, the plates self adaption reduces their size and prevents the eddies
from entering the cavity, thus, creating a dead flow region with a consequent pressure
increase at the body base.Junta de Andalucia FEDER-UJA 1262764Universidad de JaenEuropean CommissionSpanish MCIN/AEI PDC2021-121288-I00European Union Next Generation EU/PRT
PENGARUH MEDIA PEMBELAJARAN MIND MAPPING TERHADAP MINAT BELAJAR PESERTA DIDIK PADA PELAJARAN EKONOMI KELAS XI IPS 1 di SMA NEGERI 27 BANDUNG
Judul penelitian ini adalah pengaruh media pembelajaran mind
mapping terhadap minat belajar peserta didik pada pelajaran ekonomi kelas
XI IPS 1 di SMA Negeri 27 Bandung tahun ajaran 2016-2017. Berdasarkan
tinjauan langsung di SMA Negeri 27 Bandung kelas XI IPS 1, Pembelajaran
konvensional (ceramah) hanya membuat peserta didik kurang aktif dan malas
dalam menerima materi yang ada, karena pembelajaran hanya terpusat pada apa
yang disampaikan sehingga tidak dapat dimengerti secara maksimal. Tujuan dari
penelitian ini adalah: (1) Mengetahui penggunaan media mind mapping pada mata
pelajaran ekonomi kelas XI IPS 1 di SMA Negeri 27 Bandung. (2) Mengetahui
minat belajar peserta didik pada mata pelajaran ekonomi kelas XI IPS 1 di SMA
Negeri 27 Bandung. (3) Mengetahui seberapa besar pengaruh media mind
mapping terhadap minat belajar peserta didik pada mata pelajaran ekonomi kelas
XI IPS 1 di SMA Negeri 27 Bandung. Metode yang digunakan dalam penelitian
ini adalah survei. Teknik pengumpulan data yang digunakan yaitu observasi dan
angket dengan teknik pengolahan data uji validitas, uji reliabilitas, uji normalitas
data, analisis regresi linier sederhana dan koefisien determinasi, Hipotesis
penelitian berbunyi “Terdapat pengaruh antara media pembelajaran mind mapping
(X) terhadap minat belajar peserta didik (Y) pada mata pelajaran ekonomi. Hasil
penelitian ini adalah terdapat pengaruh antara variabel X dan Variabel Y sebesar
0,336 atau 33,60%. Untuk mengetahui hubungan fungsional antara variabel X dan
variabel Y maka digunakan analisis regresi linier sederhana dengan hasil
perhitungan sebagai berikut : Y = 9.915 + 0.537 X artinya bahwa setiap media
pembelajaran mind mapping bertambah 9,915 maka minat belajar meningkat
sebesar 0,537. Untuk mengetahui seberapa besar pengaruh variabel X (media
pembelajaran mind mapping) terhadap variabel Y (minat belajar), maka
digunakan koefisien determinasi dengan hasil perhitungan sebesar 33,60% maka
sebagian lainnya ditentukan oleh faktor lain yang tidak diteliti. Kesimpulan
hipotesis penelitian dapat diterima, sebagai akhir penelitian penulis
menyampaikan saran kepada guru agar sebaiknya guru menggunakan variasi
media pembelajaran yang menarik berkaitan dengan materi pelajaran yang akan
disampaikan, karena cara ini dapat membuat peserta didik aktif dan kreatif untuk
belajar. Kepada para praktisi atau peneliti lain di bidang pendidikan dapat
melakukan penelitian serupa dengan media pembelajaran dan metode yang
berbeda agar diperoleh berbagai alternatif untuk peningkatan pemahaman
pembelajaran pada pokok bahasan selanjutnya dan kepada pihak sekolah sebagai
bahan kajian bagi sekolah dan menyarankan guru untuk menggunakan media
pembelajaran yang mampu meningkatkan prestasi belajar peserta didik untuk
mendukung pendekatan saintifik dan media pembelajaran yang baik.
Kata Kunci : media pembelajaran mind mapping, minat Belajar
Searches for neutrino counterparts of gravitational waves from the LIGO/Virgo third observing run with KM3NeT
The KM3NeT neutrino telescope is currently being deployed at two different sites
in the Mediterranean Sea. First searches for astrophysical neutrinos have been performed using
data taken with the partial detector configuration already in operation. The paper presents
the results of two independent searches for neutrinos from compact binary mergers detected
during the third observing run of the LIGO and Virgo gravitational wave interferometers.
The first search looks for a global increase in the detector counting rates that could be
associated with inverse beta decay events generated by MeV-scale electron anti-neutrinos.
The second one focuses on upgoing track-like events mainly induced by muon (anti-)neutrinos
in the GeV–TeV energy range. Both searches yield no significant excess for the sources in the
gravitational wave catalogs. For each source, upper limits on the neutrino flux and on the
total energy emitted in neutrinos in the respective energy ranges have been set. Stacking
analyses of binary black hole mergers and neutron star-black hole mergers have also been
performed to constrain the characteristic neutrino emission from these categories.Grants PID2021-124591NB-C41, -C42, -C43 funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union” or by the “European Union NextGenerationEU/PRTR”Programa de Planes Complementarios I+D+I (refs. ASFAE/2022/023, ASFAE/2022/014)Programa Prometeo (PROMETEO/2020/019) and GenT (refs. CIDEGENT/2018/034, /2019/043, /2020/049. /2021/23) of the Generalitat ValencianaJunta de Andalucía (ref. SOMM17/6104/UGR, P18-FR-5057)MSC program (ref. 101025085)Programa María Zambrano (Spanish Ministry of Universities, funded by the European Union, NextGenerationEU)The European
Union’s Horizon 2020 Research and Innovation Programme (ChETEC-INFRA — Project no.
101008324)Francqui foundatio
Contribution of mangotoxin to the virulence and epiphytic fitness of Pseudomonas syringae pv. syringae
Mangotoxin is an antimetabolite toxin that inhibits ornithine acetyl transferase, a key enzyme in the biosynthetic pathway of ornithine and arginine and recently reported in strains of Pseudomonas syringae pv. syringae (Pss) isolated from mango. Since symptoms on mango tissues are very difficult to reproduce, in this study the role of mangotoxin in Pss virulence was addressed by analyzing the in planta growth and development of disease symptoms on tomato leaflets. Inoculation experiments were carried out following several procedures using the wild-type strain Pss UMAF0158, two Tn5-mutant derivative strains defective in mangotoxin production, and their complemented derivative strains in which mangotoxin production is restored. The ability of the mangotoxin-defective mutants to grow in planta was similar, and their epiphytic survival on the tomato leaf surface identical to the wild-type and complemented strains. However, both the disease index data of incidence and the severity of necrotic symptoms indicated that mangotoxin-defective mutants were less virulent, indicating that mangotoxin is a virulence factor. Furthermore, competition experiments showed that the survival values of the wild-type strain were slightly but significantly higher than those of the mangotoxin-defective mutants, suggesting that mangotoxin production would improve the epiphytic fitness of Pss. [Int Microbiol 2009; 12(2):87-95
MoS2-Carbon Nanodots as a New Electrochemiluminescence Platform for Breast Cancer Biomarker Detection
Zika virus epidemiology: From Uganda to world pandemic, an update
Zika virus (ZIKV) infection is an emergent worldwide public health problem. Historically, 84 countries have reported vector-borne ZIKV transmission, 61 of which report on-going transmission. It is a Flavivirus transmitted through arthropods belonging to the Aedes genus. Since 2015, ZIKV infections have increased dramatically; with 1.3 million people infected during 2015 in Brazil alone. This paper's objective is to highlight the conjectural epidemiological points of the virus' dissemination. The digital archives Pubmed, MEDLINE, EMBASE and Cochrane were searched for papers that assessed aspects of ZIKV transmission and epidemiology. The first isolation occurred in Uganda in 1947. Since then, important outbreaks were documented globally. Consequently, an emergent public health problem arose from a rapidly increasing incidence and its association with the development of neurological diseases such as microcephaly and Guillain-Barré syndrome. Key factors in the successful containment of outbreaks include surveillance of mosquitos in the neighbourhood, an early mosquito control treatment, an assertive information campaign, and the involvement of the local population and healthcare workers. As such, while ZIKV seems to be spreading globally in a similar manner to other arboviruses, such as Dengue and Chikungunya viruses, it can also be rapidly contained due to the pre-existing availability of necessary resources and regulatory tools as control measures. This review aims to provide a description of those characteristics of ZIKV infection that may be useful in the construction of effective outbreak control strategies. Copyright © Cambridge University Press 2018
The Possible White Dwarf-Neutron Star Connection
The current status of the problem of whether neutron stars can form, in close
binary systems, by accretion-induced collapse (AIC) of white dwarfs is
examined. We find that, in principle, both initially cold C+O white dwarfs in
the high-mass tail of their mass distribution in binaries and O+Ne+Mg white
dwarfs can produce neutron stars. Which fractions of neutron stars in different
types of binaries (or descendants from binaries) might originate from this
process remains uncertain.Comment: 6 pages. To appear in "White Dwarfs", ed. J. Isern, M. Hernanz, and
E. Garcia-Berro (Dordrecht: Kluwer
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