Statement of the Problem: Hypoxic-ischemic encephalopathy (HIE) secondary to perinatal asphyxia (PA) affects especially vulnerable brain areas such as hippocampus and is a leading cause of neonatal morbidity. During pregnancy, high-fat diet (HFD) can induce developmental changes that might enhance the risk of peripartum complications including HIE secondary to PA. Trans-resveratrol (tRESV), is a polyphenol with antioxidant properties that can be used as a maternal dietary supplement in PA. The aim of this study was to identify new epigenetic mechanisms of brain inflammation and injury related to PA, to explore the benefit of tRESV enriched maternal diet and the potential negative impact of the HFD.

Methodology & Theoretical Orientation: The hippocampal interleukin 1 beta (IL-1b), tumor necrosis factor alpha (TNFα) and S-100B protein, were assessed in postnatal day 6 rats exposed to asphyxia, the offspring of female Wistar rats expose to an enriched diet of high-fat or tRESV. The expression of non-coding microRNAs miR124, miR132, miR134, miR146 and miR15a as epigenetic markers of hippocampus response to PA was determined 24 hours post-asphyxia.

Findings: Neural response to PA could be epigenetically controlled. Maternal HFD additionally increases hippocampal TNFα, IL-1b, and S-100B after PA. PA associated with maternal HFD induces miR124 up regulation and miR132 down regulation relative to PA only. tRESV reduces asphyxia-related neuroinflammation and neural injury and down-regulates miR132 and miR15a.

Conclusion & Significance: This data supports the neuroprotective quality of tRESV when used as a supplement in the maternal diet on the offspring’s outcome in PA.HFD increases the PA-induced neuroinflammation and neuronal injury, and epigenetically influences homeostatic synaptic plasticity and neuronal tolerance to asphyxia.

Ultrasonic sensing techniques are widely used in the various scientific ultrasonic instruments using sophisticated software for various non-destructive industrial and medical applications, owing to its propagation in all kinds of medium including solids, liquids and gases except vacuum. There are many applications using ultrasonic sound in air, such as distance measurement and range imaging etc. at low cost. However, the main disadvantage is its short measurable range due to the large absorption of the ultrasonic sound in air. Another disadvantage is its bigger size. It consists of an array receiver and due to the large inter-element spacing, grating lobes appears that creates ghost images of the object. Therefore, it was the main difficulty to make it a practical product. However, because of a recent progress of Micro Electro Mechanical Systems (MEMS) technologies, it became possible to make a very small microphone array with many elements in a very small area. To extend the measurable range, some approaches were reported such as; high power sound source using spark discharge, using large scale transmitter elements and improving the signal to noise ratio (SNR) through pulse compression technique etc. In this paper, I have proposed a usage of high power ultrasonic phased array transmitter and ultrasonic array receiver using MEMS microphones for a long-range ultrasonic imaging system. The characteristics of the transmitter on the number of elements, modulated pulse width, etc. are investigated theoretically as well as experimentally. An ultrasonic array transmitter consisting of 144 (12 × 12) elements is constructed. It is controlled by four FPGAs and approximately 30 dB higher sound pressure level has been obtained than that of the single transmitter. The positions of the object are measured by delay-and-sum operations on the reflected received signal. The performance of the imaging system is compared with the system using a single transmitter. The improved 3D measurement field of an object by controlling the divergence of the ultrasonic transmitting array to improve the view angle of the system is shown. In isotropic divergence controlled system, the applied divergence is equal in both; x and y planes. In some applications a wide horizontal and narrow vertical measuring field is required. Therefore, I proposed an anisotropic divergence control system in which horizontal and the vertical divergence angles can be controlled independently. I described the principle of the anisotropic divergence control of the PAT and confirm it by numerical simulations. The anisotropic divergence of the transmitter was successfully controlled. Although, the sound pressure when the divergence was controlled 20o × 5o was about 6 dB lower than that of the PAT in phase and, 10 dB higher than the isotropic divergence controlled system and 26 dB higher than the single transmitter. The measurable range of the system with anisotropic divergence control has been improved over the isotropic divergence control by >2 m. The developed system can accurately detect the object while locating it at different positions. The maximum measurable range is > 25 m without any divergence. The developed system is useful in natural interferences e.g., smoke, fog, darkness etc. to make it a unique and novel ultrasonic long range imaging and the measurement system.

Terahertz (THz) radiations lie in electromagnetic spectrum gap between the infra-red and the microwave frequencies from 0.10 THz to 30 THz. In last few decades, generation and detection of THz radiations has attracted considerable interest not only in technological applications for THz imaging but also as a tool to investigate fundamental properties of materials by using time domain THz spectroscopy. Other applications too include information technology, biomedical sciences, non-destructive evaluation, security, quality control of foods beverage and medicines, environment monitoring and ultrafast computing etc. Much effort has been made to increase the generated terahertz radiation power. Among various methods, generation of THz radiation with the biased photoconductive switch (PCS), play very important role owing to its simple configuration and power controllability by bias and geometrical scaling. The low temperature (LT) grown GaAs PCS is most commonly used due to its sub picosecond lifetime and high mobility. Though, the THz generation efficiency is limited by its low breakdown field of about 5 x 105 V/cm. Thus, wide band gap materials with high breakdown electric fields are attractive for high power THz radiation, e.g., GaN with breakdown voltage 3.3 x 106 V/cm having high saturation velocity 2.5 x 107 V/cm and high thermal conductivity 1.3 W/cm K. Thus we investigate the most straight forward electromagnetic radiation from a GaN based large aperture LA-PCS. A carbon doped epitaxial layer was used for active region to realize high resistivity to stand high bias voltage.

THz pulses of 93.3 pJ/pulse energy was estimated at 500 V bias on excitation with 120 fs laser pulses of 266 nm wavelength with device structure as shown in fig.1. Figure 2 depicts the experimental setup with typical THz pulses and THz spectrum generated by LA GaN-PCS and measured with TDS detection.

High-performance optoelectronic devices such as lasers, light emitting diodes (LED), solar cells, and detectors can be fabricated based on the complex quantum structures of III-V semiconductors. Quantum structures such as quantum wells (QW), quantum dots (QD), and superlattices can be grown with high quality using molecular beam epitaxy (MBE). However, the interface composition abruptness is a challenge due to the surface atom intermixing. The composition asymmetry in the quantum structures leads to the non-abrupt electronic band alignments that changes the optoelectronic device properties.

For the growth temperature below 600oC, atomic arrangement in the crystal is determined by surface or near-surface processes and atoms cannot rearrange after burial. However, due to the surface mobility, atoms can displace on the growing surface. The increase of the surface mobility leads to the reduction of the growth defects; however, it may cause the so-called “surface segregation” that is the exchange between the sub-layer atoms with the impinging atoms on the growing surface. Surface segregation of atoms is driven by the differences in their binding and elastic energies. Several experimental and theoretical studies indicate that the group III atoms with weaker bond strength segregate to the surface, and therefore, it is expected to see more segregation for In atoms in comparison with Ga Atoms for similar growth conditions.  Experimental results on the well known InGaAs/GaAs system show an Indium surface enrichment due to In segregation. A similar behavior has been observed for In atoms surface segregation in InGaAs QDs embedded in GaP matrix.

We studied the concentration profile of the group-III atoms for different growth parameters using the two exchanges kinetic model and determined the critical growth temperature and growth rate regions for the growth of structures with less than 10% segregation of group-III atoms. For instance, Figure 1 illustrates the growth rate and the growth temperature regions for InAs/GaAs and GaAs/AlAs heterostructures, in which the segregation rate is less than 10%. The kinetic model results also imply that the growth temperature threshold for segregation of Ga-atoms at the normal interface into the next AlAs layer occurs at higher temperature in comparison with the In-atoms segregation into the adjacent GaAs layer