270 research outputs found
Generalized four-point characterization method for resistive and capacitive contacts
In this paper, a four-point characterization method is developed for
resistive samples connected to either resistive or capacitive contacts.
Provided the circuit equivalent of the complete measurement system is known
including coaxial cable and connector capacitances as well as source output and
amplifier input impedances, a frequency range and capacitive scaling factor can
be determined, whereby four-point characterization can be performed. The
technique is demonstrated with a discrete element test sample over a wide
frequency range using lock-in measurement techniques from 1 Hz - 100 kHz. The
data fit well with a circuit simulation of the entire measurement system. A
high impedance preamplifier input stage gives best results, since lock-in input
impedances may differ from manufacturer specifications. The analysis presented
here establishes the utility of capacitive contacts for four-point
characterizations at low frequency.Comment: 21 pages, 10 figure
Protective effect of Coriandrum sativum extract against inflammation and apoptosis in liver ischaemia/reperfusion injury
Background: The aim of this study was to investigate the anti-inflammatory and antioxidant effects of Coriandrum sativum extract on liver ischaemia reperfusion injury at light microscopic and biochemical levels.
Materials and methods: Sham, ischaemia/reperfusion injury (IRI), IRI + Coriandrum sativum extract and only Coriandrum sativum extract groups were formed. Sixty minutes of ischaemia and 60 minutes of reperfusion were performed. In the treatment group, 300 mg/kg/day Coriandrum sativum was given by gavage. Hepatic tissues were fixed in 4% paraformaldehyde. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) enzymes were measured. Nuclear factor-kappa beta (NF-ÎșB), tumour necrosis factor-alpha (TNF-α) and caspase-3 immunohistochemistry staining was performed. Microscopic scoring was performed in terms of sinusoidal congestion, vacuolisation, and necrosis.
Results: Sinusoidal enlargement and diffuse congestion, Kupffer cell increase, neutrophil increase in necrotic areas, vacuolisation in hepatocytes, and bile duct proliferation in the portal triad were observed in ischaemia/reperfusion hepatic tissue. Very rare, necrotic areas were observed in the Coriandrum sativum treatment group, while congestion and vacuolisation and bile duct proliferation were decreased compared to the ischaemic group. The AST and ALT levels were increased in the IRI and IRI + Coriandrum sativum groups. When compared to the IRI group, the AST and ALT levels of the Coriandrum sativum were considerably decreased. The IRI and IRI + Coriandrum sativum groups had statistically significant differences in ALP compared to that of the Coriandrum sativum and Sham groups. There was no significant difference between the ALP levels of the IRI and IRI + Coriandrum sativum groups TNF-α, NF-ÎșB and caspase-3 immune positive stained hepatocytes were numerous and widely observed in the injury group. There were positive TNF-α immunohistochemical staining Kupffer cells in the IRI group. In the group treated with Coriandrum sativum, Kupffer cells were not stained, while TNF-α, NF ÎșB and caspase-3 expressing hepatocytes were found to be decreased compared to the IRI group. When the expression values of the TNF-α, NF-ÎșB and caspase-3 groups were evaluated statistically, it was seen that there was a significant decrease in the group treated with Coriandrum sativum.
Conclusions: It was found that Coriandrum sativum extract decreased proinflammatory cytokine TNF-α and apoptotic cell death and liver enzymes in liver ischaemia/reperfusion injury
Fizik öÄrencileri, algoritmik problem çözĂŒcĂŒler midir yoksa kavramsal dĂŒĆĂŒnĂŒrler mi?
Bu çalıĆmada, AtatĂŒrk Ăniversitesi, Kazım Karabekir EÄitim FakĂŒltesi, Fizik EÄitimi
Anabilim Dalı, 8. Yarıyıl öÄrencilerinden seksen kiĆilik bir öÄrenci grubuna, ilk yedi yarıyılda
okutulan derslerden seçilmiĆ beĆ konu ile ilgili olarak, beĆ Ă§ift problem sorulmuĆ ve önceden
kendilerine verilmiĆ olan yöntemlerden birisini kullanarak problemlerin çözĂŒmĂŒ istenmiĆtir.
Bu öÄrencilerden âyetenekli, zekiâolanların, fiziÄin nasılından daha çok niçinini arzu ederek,
algoritmik problem çözmekten ziyade, kavramlarla ilgilenerek problemleri çözmeye
çalıĆtıkları gözlenmiĆtir
Observing and modelling the young solar analogue EK Draconis: starspot distribution, elemental abundances, and evolutionary status
Observations and modelling of stars with near-solar masses in their early
phases of evolution is critical for a better understanding of how dynamos of
solar-type stars evolve. We examine the chemical composition and the spot
distribution of the pre-main-sequence solar analogue EK Dra. Using spectra from
the HERMES Spectrograph (La Palma), we obtain the abundances of 23 elements
with respect to the solar ones, which lead to a , with
significant overabundance of Li and Ba. The s-process elements Sr, Y, and Ce
are marginally overabundant, while Co, Ni, Cu, Zn are marginally deficient
compared to solar abundances. The overabundance of Ba is most likely due to the
assumption of depth-independent microturbulent velocity. Li abundance is
consistent with the age and the other abundances may indicate distinct initial
conditions of the pre-stellar nebula. We estimate a mass of 1.04 and
an age of \,Myr using various spectroscopic and photometric
indicators. We study the surface distribution of dark spots, using 17 spectra
collected during 15 nights using the CAFE Spectrograph (Calar Alto). We also
conduct flux emergence and transport (FEAT) simulations for EK Dra's parameters
and produce 15-day-averaged synoptic maps of the likely starspot distributions.
Using Doppler imaging, we reconstruct the surface brightness distributions for
the observed spectra and FEAT simulations, which show overall agreement for
polar and mid-latitude spots, while in the simulations there is a lack of
low-latitude spots compared to the observed image. We find indications that
cross-equatorial extensions of mid-latitude spots can be artefacts of the less
visible southern-hemisphere activity.Comment: 15 pages, 16 figures, accepted for publication in MNRAS; corrections
in Abstract and Introductio
Predictions of Astrometric Jitter for Sun-like Stars. II. Dependence on Inclination, Metallicity, and Active-Region Nesting
Ultra-precise astrometry from the Gaia mission is expected to lead to
astrometric detections of more than 20,000 exoplanets in our Galaxy. One of the
factors that could hamper such detections is the astrometric jitter caused by
the magnetic activity of the planet host stars. In our previous study, we
modeled astrometric jitter for the Sun observed equator-on. In this work, we
generalize our model and calculate the photocenter jitter as it would be
measured by the Gaia and Small-JASMINE missions for stars with solar rotation
rate and effective temperature, but with various values of the inclination
angle of the stellar rotation axis. In addition, we consider the effect of
metallicity and of nesting of active regions (i.e. the tendency of active
regions to emerge in the vicinity of each other). We find that, while the
jitter of stars observed equator-on does not have any long-term trends and can
be easily filtered out, the photocenters of stars observed out of their
equatorial planes experience systematic shifts over the course of the activity
cycle. Such trends allow the jitter to be detected with continuous
measurements, in which case it can interfere with planet detectability. An
increase in the metallicity is found to increase the jitter caused by stellar
activity. Active-region nesting can further enhance the peak-to-peak amplitude
of the photocenter jitter to a level that could be detected by Gaia.Comment: 24 pages, 20 figures in the main body and 4 in the appendix, accepted
for publication in Ap
Enhanced topical delivery of dexamethasone by ÎČ-cyclodextrin decorated thermoresponsive nanogels
Highly hydrophilic, responsive nanogels are attractive as potential systems for the topical delivery of bioactives encapsulated in their three-dimensional polymeric scaffold. Yet, these drug carrier systems suffer from drawbacks for efficient delivery of hydrophobic drugs. Addressing this, ÎČ-cyclodextrin (ÎČCD) could be successfully introduced into the drug carrier systems by exploiting its unique affinity toward dexamethasone (DXM) as well as its role as topical penetration enhancer. The properties of ÎČCD could be combined with those of thermoresponsive nanogels (tNGs) based on dendritic polyglycerol (dPG) as a crosslinker and linear thermoresponsive polyglycerol (tPG) inducing responsiveness to temperature changes. Electron paramagnetic resonance (EPR) studies localized the drug within the hydrophobic cavity of ÎČCD by differences in its mobility and environmental polarity. In fact, the fabricated carriers combining a particulate delivery system with a conventional penetration enhancer, resulted in an efficient delivery of DXM to the epidermis and the dermis of human skin ex vivo (enhancement compared to commercial DXM cream: âŒ2.5 fold in epidermis, âŒ30 fold in dermis). Furthermore, DXM encapsulated in ÎČCD tNGs applied to skin equivalents downregulated the expression of proinflammatory thymic stromal lymphopoietin (TSLP) and outperformed a commercially available DXM cream
3-Benzyl-6-(2-chloroÂbenzoÂyl)-1,3-benzoxazol-2(3H)-one
In the title compound, C21H14ClNO3, the benzoxazolone ring system is planar (r.m.s. deviation = 0.022â
Ă
) and forms dihedral angles of 75.38â
(10) and 65.92â
(13)° with the mean planes of the chloroÂbenzoyl (r.m.s. deviation = 0.045â
Ă
, excluding O atom) and benzyl (r.m.s. deviation = 0.023â
Ă
) groups. The observed structure is stabilized by weak CâHâŻO hydrogen bonds and weak interÂmolecular CâHâŻÏ interÂactions
Failure to mobilize cognitive control for challenging tasks correlates with symptom severity in schizophrenia
Deficits in the adaptive, flexible control of behavior contribute to the clinical manifestations of schizophrenia. We used functional MRI and an antisaccade paradigm to examine the neural correlates of cognitive control deficits and their relations to symptom severity. Thirty-three chronic medicated outpatients with schizophrenia and 31 healthy controls performed an antisaccade paradigm. We examined differences in recruitment of the cognitive control network and task performance for Hard (high control) versus Easy (low control) antisaccade trials within and between groups. We focused on the key regions involved in âtop-downâ control of ocular motor structures â dorsal anterior cingulate cortex, dorsolateral and ventrolateral prefrontal cortex. In patients, we examined whether difficulty implementing cognitive control correlated with symptom severity. Patients made more errors overall, and had shorter saccadic latencies than controls on correct Hard vs. Easy trials. Unlike controls, patients failed to increase activation in the cognitive control network for Hard vs. Easy trials. Reduced activation for Hard vs. Easy trials predicted higher error rates in both groups and increased symptom severity in schizophrenia. These findings suggest that patients with schizophrenia are impaired in mobilizing cognitive control when presented with challenges and that this contributes to deficits suppressing prepotent but contextually inappropriate responses, to behavior that is stimulus-bound and error-prone rather than flexibly guided by context, and to symptom expression. Therapies aimed at increasing cognitive control may improve both cognitive flexibility and reduce the impact of symptoms
Gas and seismicity within the Istanbul seismic gap
Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the âIstanbul seismic gapâ) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5â5âkm depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~Mâ<â3) within the Istanbul offshore domain
High-K volcanism in the Afyon region, western Turkey: from Si-oversaturated to Si-undersaturated volcanism
Volcanic rocks of the Afyon province (eastern
part of western Anatolia) make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 Ma. The early-stage Si-oversaturated volcanic rocks around the Afyon city and further southward are trachyandesitic volcanic activity (14.23 ± 0.09 Ma). Late-stage Si-undersaturated volcanism in the southernmost part of the Afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages. Meliliteâ
leucitites (11.50 ± 0.03 Ma), spotted rachyandesites, tephryphonolites and lamproites (11.91 ± 0.13 Ma) formed in the first episode; trachyandesites in the second episode and finally phonotephrites, phonolite, basaltic trachyandesites and nosean-bearing trachyandesites during the last episode.
The parameter Q [normative q-(ne + lc + kls + ol)] of western Anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10â15 Ma.
The magmatism experienced a sudden change in the extent of Si saturation after 14 Ma, during late-stage volcanic activity of Afyon volcanic province at around 12 Ma, though there was some coexistence of Si-oversaturated and Si-undersaturated magmas during the whole life of Afyon volcanic province
- âŠ