We propose the use of Ge1−xSnx heterojunction phototransistors (HPTs) as efficient optical receivers on Si substrates and analyze their performance. Our designs use n-Ge/pGe1−xSnx/n-Ge1−xSnx layers pseudomorphically grown on Si wafers via a Ge virtual substrate, which offers compatibility with complementary metal-oxide-semiconductor (CMOS) technology. By incorporating Sn into the Ge photon-absorbing layer to shrink the bandgap, the photodetection range can be significantly extended to the mid-infrared (MIR) region with a considerably enhanced optical response. The use of HPT structures provides optical conversion gain to further enhance the optical responsivity, thereby enabling efficient photodetection in the shortwave infrared region. We develop theoretical models to calculate the composition-dependent band alignments, the band structures (by taking into account the nonparabolic effect), the absorption coefficient, and the optical responsivity for the proposed GeSn HPTs. As the Sn content increases, the conduction band nonparabolicity becomes increasingly significant and considerably impacts the optical absorption coefficient. Moreover, analysis of the spectral response for the Ge1−xSnx HPTs shows that efficient photodetection covering the entirety of the fiber-optic telecommunication bands, as well as the emerging 2 µm MIR communication band, can be achieved. These results indicate that the proposed Ge1−xSnx HPTs are attractive for use as highresponsivity CMOS-compatible photodetectors in communication applications.

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The pathogenesis of diabetic retinopathy has not been fully explained. The earliest histological lesion is the loss of intramural pericytes and thickening of the basement membrane. Increased activity of the polyol pathway is a probable mechanism for these two abnormalities. Investigations have suffered from the lack of an exact animal model simulating the human condition. Examination of the retina in the spontaneously diabetic BB-rat demonstrated degeneration and loss of intramural pericytes, a progressive increase in basement membrane thickness, and microinfarctions with areas of non-perfusion. Therefore, this model may be used to clarify the biochemical mechanism(s) linking the metabolic abnormalities of diabetes and the retinopathy.

We have solved the continuity equation for electrons in the base of an InGaP-GaAs-GaAs heterojunction bipolar transistor laser (TL) in which the position of an InGaAs quantum well (QW) in GaAs base is variable. The injected minority carrier is related to the two-dimensional carrier in QW via virtual states (VSs). The values for optical gain in the QW are obtained by considering subband energies and envelope functions in presence of strain, polarization dependent momentum matrix element and Lorentzian lineshape. Relating the gain with threshold current and the latter with base current via VS current, the threshold base current and power output from the TL are estimated. Good agreement between the calculated and the experimental threshold base currents is obtained and the match for light output power is satisfactory within experimental uncertainty. Our calculated charge distribution in the base shows similar behaviour as in the charge control analysis of the experimental data.

The principal focus of this work is the in-depth analysis of the biological efficiency of inorganic calcium-filled bacterial cellulose (BC) based hydrogel scaffolds for their future use in bone tissue engineering/bioengineering. Inorganic calcium was filled in the form of calcium phosphate (β-tri calcium phosphate (β-TCP) and hydroxyapatite (HA)) and calcium carbonate (CaCO3). The additional calcium, CaCO3 was incorporated following in vitro bio-mineralization. Cell viability study was performed with the extracts of BC based hydrogel scaffolds: BC-PVP, BC-CMC; BC-PVP-β-TCP/HA, BC-CMC-β-TCP/HA and BC-PVP-β-TCP/HA-CaCO3, BC-CMC-β-TCP/HA-CaCO3; respectively. The biocompatibility study was performed with two different cell lines, i.e., human fibroblasts, Lep-3 and mouse bone explant cells. Each hydrogel scaffold has facilitated notable growth and proliferation in presence of these two cell types. Nevertheless, the percentage of DNA strand breaks was higher when cells were treated with BC-CMC based scaffolds i.e., BC-CMC-β-TCP/HA and BC-CMC-β-TCP/HA-CaCO3. On the other hand, the apoptosis of human fibroblasts, Lep-3 was insignificant in BC-PVP-β-TCP/HA. The scanning electron microscopy confirmed the efficient adhesion and growth of Lep-3 cells throughout the surface of BC-PVP and BC-PVP-β-TCP/HA. Hence, among all inorganic calcium filled hydrogel scaffolds, ‘BC-PVP-β-TCP/HA’ was recommended as an efficient tissue engineering scaffold which could facilitate the musculoskeletal (i.e., bone tissue) engineering/bioengineering.