Hepatoprotective and antioxidant effects of Cymbopogon citratus Stapf (Lemon grass) extract in paracetamolinduced hepatotoxicity in rats

Purpose: To investigate the protective effect of Cymbopogon citrates Stapf. (CS, lemongrass) extract on paracetamol (PCM)-induced hepatotoxicity in rats.Methods: The rats were orally administered CS extract (1000 mg/kg/day) for 30 days prior to induction of hepatotoxicity by a single oral administration of PCM (3 g/kg). Hepatoprotection was assessed by measuring the level of hepatic markers including aspartate transaminase (AST), alanine transaminase (ALT) and oxidant/antioxidant markers including Malondialdehyde (MDA), protein carbonyl, and glutathione (GSH) in liver homogenate and serum. Phytochemical screening of the CS extract was also performed.Results: Phytochemical screening of the extract indicate the presence of tannins, flavonoids, and phenolic compounds. Elevation of serum AST, ALT, and MDA levels along with depletion GSH in the liver were observed in rats treated with PCM alone compared with control (p < 0.05). Pre-treatment of the animal with CS extract reduced the levels of hepatic markers (AST and ALT). Pre-treatment with CS extract also significantly reduced oxidative stress induced by PCM as shown by an increase in GSH level and reduction of MDA compared to rats treated with PCM alone (p<0.05).Conclusion: The results indicate that CS possesses antioxidant activity and it exerts its effect by reducing lipid peroxidation and restoring GSH. Pre-treatment with CS extract reduces oxidative stress and ameliorates hepatic injury induced by PCM.Keywords: Cymbopogon citratus, Antioxidant, Oxidative stress, Hepatotoxicit

Low-Power consumption Franz-Keldysh effect plasmonic modulator

In this paper we report on a low energy consumption CMOS-compatible plasmonic modulator based on Franz-Keldysh effect in germanium on silicon. We performed integrated electro-optical simulations in order to optimize the main characteristics of the modulator. A 3.3 dB extinction ratio for a 30 µm long modulator is demonstrated under 3 V bias voltage at an operation wavelength of 1647 nm. The estimated energy consumption is as low as 20 fJ/bit

Giant electro-optic effect in Ge/SiGe coupled quantum wells

International audienceSilicon-based photonics is now considered as the photonic platform for the next generation of on-chip communications. However, the development of compact and low power consumption optical modulators is still challenging. Here we report a giant electro-optic effect in Ge/SiGe coupled quantum wells. This promising effect is based on an anomalous quantum-confined Stark effect due to the separate confinement of electrons and holes in the Ge/SiGe coupled quantum wells. This phenomenon can be exploited to strongly enhance optical modulator performance with respect to the standard approaches developed so far in silicon photonics. We have measured a refractive index variation up to 2.3 × 10 −3 under a bias voltage of 1.5 V, with an associated modulation efficiency V π L π of 0.046 V cm. This demonstration paves the way for the development of efficient and high-speed phase modulators based on the Ge/SiGe material system. Silicon photonics has generated strong advances in recent years for on-chip optical communications. Silicon based-optoelectronic devices have been intensively studied and the recent advances proved the capability of silicon photonics to offer some viable solutions for many applications including optical telecommunications and optical interconnects. In this context Ge rich-Ge/SiGe quantum wells (QW) have received a growing interest since the first demonstration of the quantum-confined Stark effect (QCSE) in these structures in 200

Low-Power consumption Franz-Keldysh effect plasmonic modulator

In this paper we report on a low energy consumption CMOS-compatible plasmonic modulator based on Franz-Keldysh effect in germanium on silicon. We performed integrated electro-optical simulations in order to optimize the main characteristics of the modulator. A 3.3 $dB$ extinction ratio for a 30 ${\mu}m$ long modulator is demonstrated under 3 $V$ bias voltage at an operation wavelength of 1647 $nm$. The estimated energy consumption is as low as 20 $fJ/bit$.Comment: 8 pages, 6 figures, and 1 table. Published version: see https://doi.org/10.1364/OE.22.011236. Related works: see https://doi.org/10.1364/OE.25.010070, https://doi.org/10.1364/OE.26.030292, and https://doi.org/10.1364/OE.455491. Keywords: Integrated Optics; Silicon Photonics; Plasmonics; Modulators. arXiv admin note: text overlap with arXiv:2207.0931

Variations in neurotoxicity and proteome profile of Malayan krait (Bungarus candidus) venoms

Malayan krait (Bungarus candidus) is a medically important snake species found in Southeast Asia. The neurotoxic effects of envenoming present as flaccid paralysis of skeletal muscles. It is unclear whether geographical variation in venom composition plays a significant role in the degree of clinical neurotoxicity. In this study, the effects of geographical variation on neurotoxicity and venom composition of B. candidus venoms from Indonesia, Malaysia and Thailand were examined. In the chick biventer cervicis nerve-muscle preparation, all venoms abolished indirect twitches and attenuated contractile responses to nicotinic receptor agonists, with venom from Indonesia displaying the most rapid neurotoxicity. A proteomic analysis indicated that three finger toxins (3FTx), phospholipase A2 (PLA2) and Kunitz-type serine protease inhibitors were common toxin groups in the venoms. In addition, venom from Thailand contained L-amino acid oxidase (LAAO), cysteine rich secretory protein (CRISP), thrombin-like enzyme (TLE) and snake venom metalloproteinase (SVMP). Short-chain post-synaptic neurotoxins were not detected in any of the venoms. The largest quantity of long-chain post-synaptic neurotoxins and non-conventional toxins was found in the venom from Thailand. Analysis of PLA2 activity did not show any correlation between the amount of PLA2 and the degree of neurotoxicity of the venoms. Our study shows that variation in venom composition is not limited to the degree of neurotoxicity. This investigation provides additional insights into the geographical differences in venom composition and provides information that could be used to improve the management of Malayan krait envenoming in Southeast Asia

Silicon nitride waveguide-integrated Ge/SiGe quantum wells optical modulator

Silicon-based photonics has generated a strong interest in recent years, mainly for optical interconnects and sensing on photonic integrated circuits. The main rationales of silicon photonics are the reduction of energy consumption and photonic system costs via integration on a standard Si chip. Waveguide-integrated silicon based-optoelectronic modulators have been particularly studied as a key building block. Ge-rich Ge/SiGe quantum well waveguides are promising for compact and low energy consumption modulators thanks to the demonstration of direct gap related optical transitions in these structures, while silicon nitride (SiN) waveguide could be a promising alternative to Si waveguide. This paper studies an integration approach between passive SiN waveguide and active Ge/SiGe multiple quantum wells (MQWs) optoelectronic modulators. Photocurrent measurements at different bias voltages demonstrated strong optical modulation within the O-band wavelength (1.26 - 1.36 μm) from Ge/SiGe MQWs, while 3D-FDTD calculations confirm a compact and efficient integration with SiN waveguide on Si wafer

Global transition path search for dislocation formation in Ge on Si(001)

Global optimization of transition paths in complex atomic scale systems is addressed in the context of misfit dislocation formation in a strained Ge film on Si(001). Such paths contain multiple intermediate minima connected by minimum energy paths on the energy surface emerging from the atomic interactions in the system. The challenge is to find which intermediate states to include and to construct a path going through these intermediates in such a way that the overall activation energy for the transition is minimal. In the numerical approach presented here, intermediate minima are constructed by heredity transformations of known minimum energy structures and by identifying local minima in minimum energy paths calculated using a modified version of the nudged elastic band method. Several mechanisms for the formation of a 90{\deg} misfit dislocation at the Ge-Si interface are identified when this method is used to construct transition paths connecting a homogeneously strained Ge film and a film containing a misfit dislocation. One of these mechanisms which has not been reported in the literature is detailed. The activation energy for this path is calculated to be 26% smaller than the activation energy for half loop formation of a full, isolated 60{\deg} dislocation. An extension of the common neighbor analysis method involving characterization of the geometrical arrangement of second nearest neighbors is used to identify and visualize the dislocations and stacking faults

O-band quantum-confined Stark effect optical modulator from Ge/Si0.15Ge0.85 quantum wells by well thickness tuning

open7openPapichaya Chaisakul; Jacopo Frigerio; Delphine Marris-Morini; Vladyslav Vakarin; Daniel Chrastina; Giovanni Isella; Laurent VivienPapichaya, Chaisakul; Frigerio, Jacopo; Delphine Marris, Morini; Vladyslav, Vakarin; Chrastina, Daniel; Isella, Giovanni; Laurent, Vivie

Photo-detectors integrated with resonant tunneling diodes

We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.FCT under the project WOWi [PTDC/EEA-TEL/100755/2008]; programme POCTI/FEDER [REEQ/1272/EEI/2005]; FCT Portugal [SFRH/BPD/84466/2012]info:eu-repo/semantics/publishedVersio