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Numerical investigation of thermal behavior of AlGaN/GaN HEMTs on SiC, Si and Sapphire substrates
No full textIn this letter, thermal analysis results of AlGaN/GaN HEMTs grown on
SiC, Si and Sapphire substrates were presented. Accurate channel
temperature determination and temperature distribution were carried out
using 3-D finite element model for both steady state and transient
cases. Present simulation results are in good agreement with
experimental data from the literature. Effect of different device
parameters such as substrate thickness, gate length, gate width,
dissipated power and pulse width were investigated to determine in which
range of these parameters GaN-devices provide the best thermal
performance. Resulting thermal resistance values have been extracted for
different substrates. For single-finger devices grown on Sapphire, Si
and SiC substrates, thermal resistances were calculated as follows; 158
degrees C/W, 53.5 degrees C/W and 26.3 degrees C/W, respectively.
According to our results, channel temperature is defined as a function
of power, gate length, gate width and substrate thickness, for the
device grown on SiC that has the best thermal performance. In addition,
transient thermal performance was studied for sub micrometer pulse
width, and substrate material performances are compared. It is expected
that this study facilitates the improvement of AlGaN/GaN HEMTs design to
reduce thermal resistance, and also improves the reliability and
life-time of these devices
A comparative study on utilizing hybrid-type nanofluid in plate heat exchangers with different number of plates
No full textDifferent methods have been utilized to enhance the thermal efficiency
of the heat exchangers (HEs). A widely used method to upgrade the
thermal efficiency of HEs is upgrading the thermal properties of working
fluid by utilizing nanoparticles. In this study, Al(2)O(3)and CuO have
been utilized to prepare Al2O3-CuO/water hybrid nanofluid. Accordingly,
Al(2)O(3)and CuO nanoparticles have been mixed into the water with 1\%
(50:50) weight concentration. The main objective of this work is testing
the prepared hybrid nanofluid in plate-type HEs (PHEs) with 8, 12 and 16
plates to determine the influence of number of plates on heat transfer
improvement by hybrid nanofluid. Experimental findings of the present
study demonstrated that utilizing Al2O3-CuO/water hybrid-type nanofluid
in the PHE enhanced thermal efficiency notably in comparison with
single-type nanofluids. Using this hybrid nanofluid increased the
thermal performance in all PHEs with different number of plates.
However, it is observed that increasing number of plates led to more
increment in thermal performance by utilizing hybrid nanofluid. The
highest increment in overall heat transfer coefficient was obtained as
12\%, 19\% and 20\% in PHEs with eight, 12 and 16 plates, respectively.
In addition, the highest enhancement in effectiveness was achieved as
10\%, 11.7\% and 16\% in PHEs with eight, 12 and 16 plates,
respectively
The Association of Left Ventricular End-Diastolic Pressure and Acute Left Ventricular End-Diastolic Pressure Change with Miyocardial Blush Grade and ST Segment Resolution in STEMI Patients Undergoing Primary Percutaneous Intervention
No full textFarklı Karayolu Tünellerinin Tünel Özellikleri ve Sürücü Davranışları Açısından İrdelenmesi
No full textEffect of plasma treatment on the peel bond strength between maxillofacial silicones and resins
No full text
Prediction of gestational diabetes mellitus in the first trimester: comparison of maternal fetuin-A, N-terminal proatrial natriuretic peptide, high-sensitivity C-reactive protein, and fasting glucose levels (vol 63, pg 121, 2019)
No full textNatural products, PGC-1 alpha, and Duchenne muscular dystrophy
No full textPeroxisome proliferator-activated receptor gamma (PPAR gamma) is a
transcriptional coactivator that binds to a diverse range of
transcription factors. PPAR gamma coactivator 1 (PGC-1) coactivators
possess an extensive range of biological effects in different tissues,
and play a key part in the regulation of the oxidative metabolism,
consequently modulating the production of reactive oxygen species,
autophagy, and mitochondrial biogenesis. Owing to these findings, a
large body of studies, aiming to establish the role of PGC-1 in the
neuromuscular system, has shown that PGC-1 could be a promising target
for therapies targeting neuromuscular diseases. Among these, some
evidence has shown that various signaling pathways linked to PGC-1 alpha
are deregulated in muscular dystrophy, leading to a reduced capacity for
mitochondrial oxidative phosphorylation and increased reactive oxygen
species (ROS) production. In the light of these results, any
intervention aimed at activating PGC-1 could contribute towards
ameliorating the progression of muscular dystrophies. PGC-1 alpha is
influenced by different patho-physiological/pharmacological stimuli.
Natural products have been reported to display modulatory effects on
PPAR gamma activation with fewer side effects in comparison to synthetic
drugs. Taken together, this review summarizes the current knowledge on
Duchenne muscular dystrophy, focusing on the potential effects of
natural compounds, acting as regulators of PGC-1 alpha. (C) 2020 Chinese
Pharmaceutical Association and Institute of Materia Medica, Chinese
Academy of Medical Sciences. Production and hosting by Elsevier B.V
Gut-lung axis and dysbiosis in COVID-19
No full textCOVID-19, a novel infectious disease, caused by SARS-CoV-2, affected
millions of people around the world with a high mortality rate. Although
SARS-CoV-2 mainly causes lung infection, gastrointestinal symptoms
described in COVID-19 patients and detection of the viral RNA in feces
of infected patients drove attentions to a possible fecal-oral
transmission route of SARS-CoV-2. However, not only the viral RNA but
also the infectious viral particles are required for the viral infection
and no proof has been demonstrated the transmission of the infectious
virus particles via the fecal-oral route yet. Growing evidence indicates
the crosstalk between gut microbiota and lung, that maintains host
homeostasis and disease development with the association of immune
system. This gut-lung interaction may influence the COVID-19 severity in
patients with extrapulmonary conditions. Severity of COVID-19 has mostly
associated with old ages and underlying medical conditions. Since the
diversity in the gut microbiota decreases during aging, dysbiosis could
be the reason for older adults being at high risk for severe illness
from COVID-19. We believe that gut microbiota contributes to the course
of COVID-19 due to its bidirectional relationship with immune system and
lung. Dysbiosis in gut microbiota results in gut permeability leading to
secondary infection and multiple organ failure. Conversely, disruption
of the gut barrier integrity due to dysbiosis may lead to translocation
of SARS-CoV-2 from the lung into the intestinal lumen via circulatory
and lymphatic system. This review points out the role of dysbiosis of
the gut microbiota involving in sepsis, on the severity of SARS-CoV-2
infection. Additionally, this review aims to clarify the ambiguity in
fecal-oral transmission of SARS- CoV-2