119 research outputs found
Three New Records of Gall Midges (diptera: Cecidomyiidae) from Turkiye
No full textTataroglu, Musa/0000-0002-9621-9909Three new records for the Turkish gall midges (Diptera: Cecidomyiidae) fauna were obtained for the first time from the seeds of Salvia sclarea L. collected during a field study in Denizli province, Turkiye. These new records are as follows: Arthrocnodax salviae Fedotova, 1995, Dasineura salviae (Kieffer, 1909) and Lasioptera salviae Schiner, 1868. The locations of the determined species in Turkiye, their world distribution and host plant data are provided
Studying circadian rhythms in Drosophila melanogaster
No full textCircadian rhythms have a profound influence on most bodily functions: from metabolism to complex behaviors. They ensure that all these biological processes are optimized with the time-of-day. They are generated by endogenous molecular oscillators that have a period that closely, but not exactly, matches day length. These molecular clocks are synchronized by environmental cycles such as light intensity and temperature. Drosophila melanogaster has been a model organism of choice to understand genetically, molecularly and at the level of neural circuits how circadian rhythms are generated, how they are synchronized by environmental cues, and how they drive behavioral cycles such as locomotor rhythms. This review will cover a wide range of techniques that have been instrumental to our understanding of Drosophila circadian rhythms, and that are essential for current and future research
The C-V-f and G/omega-V-f characteristics of Al/SiO2/p-Si (MIS) structures
No full textThe frequency dependence of capacitance-voltage (C-V) and conductance-voltage (G/omega-V) characteristics of the Al/SiO2/p-Si metalinsulator-semiconductor (MIS) structures has been investigated taking into account the effect of the series resistance (R,) and interface states (N-ss) at room temperature. The C-V and G/omega-V measurements have been carried out in the frequency range of 1 kHz to 1 MHz. The frequency dispersion in capacitance and conductance can be interpreted only in terms of interface states and series resistance. The N-ss can follow the ac signal and yield an excess capacitance especially at low frequencies. In low frequencies, the values of measured C and G/omega decrease in depletion and accumulation regions with increasing frequencies due to a continuous density distribution of interface states. The C-V plots exhibit anomalous peaks due to the N-ss and R-s, effect. It has been experimentally determined that the peak positions in the C-V plot shift towards lower voltages and the peak value of the capacitance decreases with increasing frequency. The effect of series resistance on the capacitance is found appreciable at higher frequencies due to the interface state capacitance decreasing with increasing frequency. In addition, the high-frequency capacitance (C-m) and conductance (G(m)/omega) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance. Experimental results show that the locations of N-ss and R-s have a significant effect oil electrical characteristics of MIS structures. (c) 2006 Elsevier B.V. All rights reserved
The molecular ticks of the Drosophila circadian clock
No full textDrosophila is a powerful model to understand the mechanisms underlying circadian rhythms. The Drosophila molecular clock is comprised of transcriptional feedback loops. The expressions of the critical transcriptional activator CLK and its repressors PER and TIM are under tight transcriptional control. However, posttranslational modification of these proteins and regulation of their stability are critical to their function and to the generation of 24-hr period rhythms. We review here recent progress made in our understanding of PER, TIM and CLK posttranslational control. We also review recent studies that are uncovering the importance of novel regulatory mechanisms that affect mRNA stability and translation of circadian pacemaker proteins and their output
Oxidative/antioxidative status, lymphocyte DNA damage, and urotensin-2 receptor level in patients with migraine attacks
No full textMehmet Yigit,1 Ozgur Sogut,1 Özlem Tataroglu,1 Adnan Yamanoglu,1 Eda Yigit,2 Eray Metin Güler,3 Omer Faruk Ozer,3 Abdurrahim Kocyigit3 1Department of Emergency Medicine, Haseki Training and Research Hospital, University of Health Sciences, 2Department of Emergency Medicine, Sisli Hamidiye Etfal Training and Research Hospital, University of Health Sciences, 3Department of Biochemistry, Faculty of Medicine, Bezmialem Vakif University, Istanbul, Turkey Background: The present study investigated the potential roles of plasma lymphocyte DNA damage, the urotensin-2 receptor (UTS2R), and oxidative changes in patients with varying degrees of migraine-related disability who were in the ictal phase and presented to our emergency department. Methods: This study enrolled 40 consecutive adult patients with migraine attack and 40 age- and sex-matched healthy controls. The same health care professional determined the headache-related disability of each patient’s migraine attack using the Migraine Disability Assessment Scale (MIDAS); patients were divided into three groups based on MIDAS score. Plasma lymphocyte DNA damage; UTS2R, malondialdehyde (MDA), and catalase (CAT) levels; total oxidant status (TOS); total antioxidant status (TAS); and the oxidative stress index (OSI) were used as predictors of early oxidative changes. Results: Plasma lymphocyte DNA damage, TOS, MDA levels, and OSI values were significantly higher in patients with migraine compared to controls. Conversely, TAS and CAT and UTS2R levels were markedly lower in patients with migraine compared to controls. Comparisons of the patient groups by MIDAS score revealed significant differences in plasma lymphocyte DNA damage and CAT levels but no differences in TOS, MDA levels, OSI, TAS, or UTS2R levels. MIDAS scores were positively correlated with the degree of lymphocyte DNA damage, but neither of these factors was significantly related to CAT levels. Conclusion: The present data suggest that lymphocyte DNA damage and changes in oxidative/antioxidative status may reflect an enhanced oxidative damage and an ineffective antioxidant defense system in migraineurs during headache attacks. In addition, lymphocyte DNA damage levels may be an indicator of the degree of migraine-related disability as assessed by MIDAS score. Keywords: migraine attack, oxidative/antioxidative changes, lymphocyte DNA damage, urotensin-2 receptor, Migraine Disability Assessment Scal
Impedance spectroscopy of Au/TiO2/n-Si metal-insulator-semiconductor (MIS) capacitor
No full textIn this study, the electrical properties of Au/TiO2/n-Si metal-insulator-semiconductor (MIS) capacitor were investigated by impedance spectroscopy (IS) technique. Impedance measurements were performed in the frequency range of 10 Hz-1 MHz for various bias voltages. The Cole-Cole plots show a single dielectric relaxation. The equivalent circuit was estimated from the shape of the Cole-Cole plots. The equivalent circuit of the MIS capacitor consists of a parallel resistor (R-p) and capacitor (C-p) in series with a resistor (R-s). It is observed that the Cole-Cole plots indicate a semicircle. The parameters of the equivalent circuit were determined by fitting the impedance measurement data. While the R-p value decreases with increasing the bias voltage, the C-p and R-s value are almost independent of the bias voltage. From the variation of log(R-p) with log(V), the dominant conduction mechanism of the MIS capacitor was determined as space-charge limited current (SCLC) mechanism
Analysis of density and time constant of interface states of MIS device by conductance method
No full textThe density and time constant of interface states of Au/Si3N4/n-Si (MIS) device have been analyzed by conductance method. The capacitance and conductance measurements of the device have been performed at various frequencies in the range of 1 kHz-1 MHz. Experimental results show that Gp/ω-log(f) plots for each voltage value give a peak because of the presence of interface states. The density (Nss) and time constant () of interface states have been calculated from maximum value of the peak. The values of Nss and range from 2.49×1013 eV-1cm-2 to 7.57×1012 eV-1cm-2 and from 2.67×10-5s to 1.67×10-5s, respectively
Role of Glycogen Synthase Kinase (GSK) in temperature compensation of the Neurospora circadian clock
No full textCircadian clocks are biological oscillators that allow organisms to accurately predict and adjust to the rhythmic changes in the environment which increases their fitness. These oscillators are found in every cell and have three fundamental properties: they are endogenous, entrainable and temperature compensated. The former two properties of the clock are well studied. However, it is currently unknown how clocks accurately keep the time independent of the ambient temperature, a phenomenon known as “temperature compensation”. This is particularly important for poikilothermic organisms that cannot control their body temperature and yet still have accurate circadian clocks. We used Neurospora crassa as a eukaryotic circadian clock model organism and showed that Glycogen synthase kinase (GSK) binds and specifically phosphorylates White Collar 1 (WC-1), which is the critical and rate-limiting positive element of the Neurospora clock. We found that these phosphorylations decrease the WC-1 stability in a temperature dependent manner. Our data completes the picture in our current understanding of temperature compensation of circadian clocks and shows that temperature compensation in Neurospora crassa is achieved by opposing functions of two kinases (GSK and CK2) on the positive (WCC) and negative (FRQ) elements of the clock, respectively. Since both kinases are well conserved among eukaryotes, it is also possible that this mechanism of temperature compensation is conserved among other eukaryotic circadian clocks
Electrical characterization of silicon nitride interlayer-based MIS diode
No full textIn this study, silicon nitride (Si3N4) thin film on p-type GaAs wafer was deposited by RF magnetron sputtering. The surface morphology of Si3N4/GaAs structure was analyzed by atomic force microscopy (AFM). The electrical characteristics of the fabricated Au/Si3N4/p-GaAs metal-insulator-semiconductor (MIS) diode were investigated by using current-voltage (I-V) measurements at room temperature. The electronic parameters such as ideality factor (n) and barrier height (phi(bo)) of the MIS diode were derived using thermionic emission (TE). The phi(bo) was also extracted from Norde method. The barrier height values obtained from both TE and Norde were found to be in harmony with each other. The interface state density (N-ss) and series resistance (R-s) parameters of the MIS diode were determined from the measured I-V data. In addition, the dominant current conduction mechanisms of the MIS diode were also investigated by forward bias ln(I-F) - ln(V-F) and reverse bias ln(I-R) - V-R(0.5) plot. At high forward bias, the current conduction was associated with the space charge limited current (SCLC). At reverse bias region, the current conduction was associated with the Schottky emission (SE)
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