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Automated Design of Tissue Engineering Scaffolds by Advanced CAD
The design of scaffolds with an intricate and controlled internal structure represents a
challenge for Tissue Engineering. Several scaffold manufacturing techniques allow the
creation of complex and random architectures, but have little or no control over geometrical
parameters such as pore size, shape and interconnectivity- things that are essential for tissue
regeneration. The combined use of CAD software and layer manufacturing techniques allow
a high degree of control over those parameters, resulting in reproducible geometrical
architectures. However, the design of the complex and intricate network of channels that are
required in conventional CAD, is extremely time consuming: manually setting thousands of
different geometrical parameters may require several days in which to design the individual
scaffold structures. This research proposes an automated design methodology in order to
overcome those limitations. The combined use of Object Oriented Programming and
advanced CAD software, allows the rapid generation of thousands of different geometrical
elements. Each has a different set of parameters that can be changed by the software, either
randomly or according to a given mathematical formula, so that they match the different
distribution of geometrical elements such as pore size and pore interconnectivity.
This work describes a methodology that has been used to design five cubic scaffolds with
pore size ranging from about 200 to 800 µm, each with an increased complexity of the
internal geometry.Mechanical Engineerin
Optimization of a solar air heater with phase change materials: Experimental and numerical study
In this paper, a solar air heater (SAH) with phase change material (PCM)-based energy storage is investigated. Paraffin was placed underneath the absorber plate as the PCM. A transient two-dimensional laminar model was used in the Ansys Fluent 17 software to study the effects of different parameters on the performance of the SAH, such as the air mass flow rate, the amount of paraffin, and the thermal conductivity of the paraffin. The performance of the SAH was optimized by considering two objectives simultaneously: thermal energy efficiency and maximum nocturnal temperature difference between the inlet and the outlet of the SAH. To validate the numerical model, a SAH with a 2-cm paraffin layer and the same dimensions as the numerical model was built and tested. The results of the simulation showed good agreement with the experimental results.
Translocation through environments with time dependent mobility
We consider single particle and polymer translocation where the frictional
properties experienced from the environment are changing in time. This work is
motivated by the interesting frequency responsive behaviour observed when a
polymer is passing through a pore with an oscillating width. In order to
explain this better we construct general diffusive and non-diffusive frequency
response of the gain in translocation time for a single particle in changing
environments and look at some specific variations. For two state confinement,
where the particle either has constant drift velocity or is stationary, we find
exact expressions for both the diffusive and non-diffusive gain. We then apply
this approach to polymer translocation under constant forcing through a pore
with a sinusoidally varying width. We find good agreement for small polymers at
low frequency oscillation with deviations occurring at longer lengths and
higher frequencies. Unlike periodic forcing of a single particle at constant
mobility, constant forcing with time dependent mobility is amenable to exact
solution through manipulation of the Fokker-Planck equation.Comment: 9 pages, 5 figure
Rational points on compactifications of semi-simple algebraic groups
We prove Manin's conjecture concerning the distribution of rational points of
bounded height, and its refinement by Peyre, for wonderful compactifications of
semi-simple algebraic groups over number fields. The proof proceeds via the
study of the associated height zeta function and its spectral expansion
Efficiency Improvement of Fault-Tolerant Three-Level Power Converters
Fault-tolerant power converters play a critical role in the transportation electrification. However, fault-tolerant operation, high efficiency, and low cost usually result in design criteria that have conflicting constraints and goals. The majority of the fault-tolerant power converter topologies presented in the literature confirm these conflicts. In this paper, three types of fault-tolerant neutral-point clamped (NPC) converters are investigated. Various modulation strategies are explored to reduce the losses of the redundant phase leg. The simulation and experimental results show that the Switching Frequency Optimal Phase opposition Disposition modulation strategy is the most effective approach in minimizing the losses in the redundant phase leg
Galaxy formation with cold gas accretion and evolving stellar initial mass function
The evolution of the galaxy stellar mass function is especially useful to
test the current model of galaxy formation. Observational data have revealed a
few inconsistencies with predictions from the model. For
example, most massive galaxies have already been observed at very high
redshifts, and they have experienced only mild evolution since then. In
conflict with this, semi-analytical models of galaxy formation predict an
insufficient number of massive galaxies at high redshift and a rapid evolution
between redshift 1 and 0 . In addition, there is a strong correlation between
star formation rate and stellar mass for star-forming galaxies, which can be
roughly reproduced with the model, but with a normalization that is too low at
high redshift. Furthermore, the stellar mass density obtained from the integral
of the cosmic star formation history is higher than the measured one by a
factor of 2. In this paper, we study these issues using a semi-analytical model
that includes: 1) cold gas accretion in massive halos at high redshift; 2)
tidal stripping of stellar mass from satellite galaxies; and 3) an evolving
stellar initial mass function (bottom-light) with a higher gas recycle
fraction. Our results show that the combined effects from 1) and 2) can predict
sufficiently massive galaxies at high redshifts and reproduce their mild
evolution at low redshift, While the combined effects of 1) and 3) can
reproduce the correlation between star formation rate and stellar mass for
star-forming galaxies across wide range of redshifts. A bottom-light/top-heavy
stellar IMF could partly resolve the conflict between the stellar mass density
and cosmic star formation history.Comment: 9 pages, 7 figures. Accepted for publication in Ap
Satellite Luminosities in Galaxy Groups
Halo model interpretations of the luminosity dependence of galaxy clustering
assume that there is a central galaxy in every sufficiently massive halo, and
that this central galaxy is very different from all the others in the halo. The
halo model decomposition makes the remarkable prediction that the mean
luminosity of the non-central galaxies in a halo should be almost independent
of halo mass: the predicted increase is about 20% while the halo mass increases
by a factor of more than 20. In contrast, the luminosity of the central object
is predicted to increase approximately linearly with halo mass at low to
intermediate masses, and logarithmically at high masses. We show that this
weak, almost non-existent mass-dependence of the satellites is in excellent
agreement with the satellite population in group catalogs constructed by two
different collaborations. This is remarkable, because the halo model prediction
was made without ever identifying groups and clusters. The halo model also
predicts that the number of satellites in a halo is drawn from a Poisson
distribution with mean which depends on halo mass. This, combined with the weak
dependence of satellite luminosity on halo mass, suggests that the Scott
effect, such that the luminosities of very bright galaxies are merely the
statistically extreme values of a general luminosity distribution, may better
apply to the most luminous satellite galaxy in a halo than to BCGs. If galaxies
are identified with halo substructure at the present time, then central
galaxies should be about 4 times more massive than satellite galaxies of the
same luminosity, whereas the differences between the stellar M/L ratios should
be smaller. Therefore, a comparison of the weak lensing signal from central and
satellite galaxies should provide useful constraints. [abridged]Comment: 8 pages, 3 figures. Matches version accepted by MNRA
Изучение терапевтических эффектов излучения с длиной волны 670 нм при различных типах диабетического макулярного отека
The purpose of this study was to investigate the therapeutic effects of 670 nm irradiation in patients with diabetic macular edema. In several studies, positive effects of red/near-infrared irradiation showed in a range of ocular diseases such as macular degeneration, macular edema, and retinitis pigmentosa. This study was conducted on forty five eyes of 26 diabetic patients with macular edema between the ages of 51 and 80.Measurement of visual acuity and slit lamp examination, funduscopy, and optical coherence tomography were performed in all subjects. None of the patients had proliferative retinopathy. We used a portable LED device (Warp 10, Quantum Devices) for treatment. Patients held this device at a distance of 3 cm from their eyes for 240 seconds for three months. Full ophthalmic examinations were repeated 1, 2, and 3 months after treatment.After 3 months, the mean visual acuity improved from 0.44 ± 0.38 log MAR to 0.27 ± 0.24 log MAR and vision increased by 1.52 ± 1.16 lines post treatment (р<0.001). The mean central macula thickness decreased from 381.49 ± 144.40 μm to 359.72 ± 128.84 μm (р=0.050). In patients with mild and moderate nonproliferative diabetic retinopathy, the mean central retinal thickness decreased 52.06 ± 67.78 μm and 39.27 ± 44.69 μm, respectively, but patients with severe type showed an increase of 34.93 ± 65.65 μm in the mean central retinal thickness (р<0.001). Also, the severity of macular edema had no effect on final outcomes (р>0.05). Photobiomodulation can positively affect diabetic macular edema, especially in patients with mild to moderate diabetic retinopathy.Целью данной исследовательской работы являлось изучение терапевтических эффектов излучения с длиной волны 670 нм у пациентов с диабетическим макулярным отеком. Ряд предыдущих исследований свидетельствует о положительном эффекте красного инфракрасного излучения при некоторых заболеваниях глаз, таких как макулодистрофия (дегенерация желтого пятна), макулярный отек и пигментный ретинит. Наше исследование было проведено на 45 глазах у 26 больных сахарным диабетом в возрасте от 51 до 80 лет с макулярным отеком. Всем пациентам были проведены определение остроты зрения, осмотр глаз щелевой лампой, фундоскопия и оптическая когерентная томография. Ни у одного из пациентов не было пролиферативной ретинопатии. Для лечения нами был применен портативный светодиодный прибор (Warp 10, Quantum devices). Пациенты держали светодиод на расстоянии 3 см от глаза в течение 240 сек в течение 3 мес. Все офтальмологические исследования были повторены через 1, 2 и 3 мес после проведения лечебной процедуры. Через 3 мес средняя острота зрения улучшилась с показателем логарифма минимального угла разрешения 0,44 ± 0,38 до 0,27 ± 0,24, что показало увеличение показателя остроты зрения на 1,52 ± 1,16 после лечения (р<0,001). Средняя центральная толщина сетчатки в области макулы уменьшилась с 381,49 ± 144,40 мкм до 359,72 ± 128,84 мкм (р=0,050). У пациентов с легкой и умеренной непролиферативной диабетической ретинопатией средняя толщина сетчатки уменьшилась до 52,06 ± 67,78 и 52,06 ± 67,78 мкм, соответственно, а у пациентов с тяжелой ретинопатией наблюдалось увеличение на 34,93 ± 65,65 мкм (р<0,001). Помимо того, степень макулярного отека не повлияла на окончательный результат лечения (р>0,05). Фотобиомодуляция была эффективной при диабетическом макулярном отеке, в частности, у пациентов с легкой и умеренной диабетической ретинопатией
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