Fabrication of silk-based composite scaffold for bone-ligament-bone graft using aqueous polymeric dispersion technique

Tissue engineering is a promising technology for treating tissue defects or replacing nonfunctional tissues/organs. It relies upon a temporary scaffold that is basically an artificial structure which provides the support for 3D tissue formation or organogenesis. Ideally, scaffolds should be able to accommodate human cells, orchestrate their growth and differentiation leading to tissue regeneration and ultimately make it feasible for implantation. Major sports injuries involve the damage of cartilages, ligaments, tendons and the enthesis. Since ligament injury is most common and ligament-alone grafts are not so successful to replace the injured ligaments, the researchers are experimenting with the construction of a composite scaffold which can guide the stem cells to differentiate into fibrocartilage that bridges of Bone-Ligament interface i.e. enthesis. In the current project, a composite silk-based scaffold was fabricated by incorporating multiple compartments for B-L-B graft. The core scaffold was prepared by knitting the silk fibers (from Bombyx mori) to provide required mechanical strength. The individual compartments over the knitted scaffold were coated with specific biocompatible components (i.e. hydroxyapatite for bone, Polyethylene oxide and & Polyethylene glycol for ligament and cartilage) blended with gelatin using Aqueous Polymer Dispersion (APD) Technique. The morphology of fabricated scaffolds was studied under optical microscope and SEM (Scanning Electron Microscope) while the mechanical properties were analysed through the Texture Analyzer. The particle sizes were found to be between 10-1000 nm. It was concluded that silk based multi-compartmental scaffolds fabricated from APD technique are suitable for enthesis tissue engineering due to their porosity and matching mechanical properties. However, the scaffolds need to be confirmed for their bioactivity by culturing live cells on respective compartment

Local stresses in plated structures

Imperial Users onl

Binary Multifunctional Ultrabroadband Self-Powered g-C3N4 /Si Heterojunction High-Speed Photodetector

Compact optical detectors with fast binary photoswitching over a broad range of wavelength are essential as an interconnect for any light-based parallel, real-time computing. Despite of the tremendous technological advancements yet there is no such single device available that meets the specifications. Here we report a multifunctional self-powered high-speed ultrabroadband (250-1650 nm) photodetector based on g-C3N4/Si hybrid 2D/3D structure. The device shows a novel binary photoswitching (change in current from positive to negative) in response to OFF/ON light illumination at small forward bias (<0.1 V) covering 250-1350 nm. At zero bias, the device displays an extremely high ON/OFF ratio of 1.2 x 10^5 under 680 nm (49 microWcm-2) illumination. The device also shows an ultrasensitive behaviour over the entire operating range at low light illuminations, with highest responsivity (1.2 AW-1), detectivity (2.8 x 10^14 Jones) and external quantum efficiency (213%) at 680 nm. The response and recovery speeds are typically 0.23 and 0.60 ms, respectively, under 288 Hz light switching frequency. Dramatically improved performance of our device is attributed to the heterojunctions formed by the ultrathin g-C3N4 nanosheets embedded in the Si surface.Comment: 21 page, 8 figures, 3 table

Human Tracking and Activity Recognition for Surveillence Applications

Tracking and study of behavioural changes of human beings through vision is a challenging task. For surveillance, automated systems are important which can observe the traffic and can detect the abnormality. For tracking human or any kind of object, colour feature based mean shift technique is widely used. This technique uses Bhattacharya coefficient to locate the object based on the maximisation of the similarity function between object model and candidate model. Traditional mean shift algorithm fails when the object having large motion, occlusion, corrupted frames etc. In addition to that, the technique is not automatic to initiate the tracking. To overcome all these problems, this thesis work proposed a technique which uses three additional modules to the traditional method to make it more efficient. The proposed modules used human detection by modelling through star skeletonization, followed by block search algorithm and occlusion handling. Block search algorithm helped to supply an overlapping area to candidate model to continue the track when tracking fails due to fast motion. Occlusion handling helped in initiating the tracking after prolonged period of occlusion. The proposed method has been tested on real time data and it outperforms the conventional method effectively to overcome the mentioned problems up to large extent. Human activity recognition is a hierarchical procedure which confirms abnormality step by step. Low level activity recognition is a trajectory based application in which trajectory of tracks of a human being helps to detect the abnormal events like person fell down, illegal entry, abnormal loitering, line formation etc. At high level, human pose will be detected by the help of shape based human pose detection. The main aim of the system is to make a person independent real-time human activity recognition with decreased false alarm rates

RF Power Amplifier and Its Envelope Tracking

This dissertation introduces an agile supply modulator with optimal transient performance for the envelope tracking supply in linear power amplifiers. For this purpose, an on-demand current source module, the bang-bang transient performance enhancer (BBTPE), is proposed. Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further assists the proposed system to reduce both overshoot and settling time. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results for a PA using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in ACPR and EVM, respectively. In a polar power amplifier, the input signal splits into phase and amplitude components using a non-linear conversion operation. This operation broadens the spectrum of the polar signal components. The information of amplitude and phase contains spectral images due to the sampling operation in non-linear conversion operation. These spectral images can be large and cause out-of-band emission in the output spectrum. In addition, during the recombination process of phase and amplitude, a delay mismatch between amplitude and phase signals, which can occur due to separate processing paths of amplitude and phase signals, causes out-of-band emissions, also known as spectral regrowth. This dissertation presents solutions to both of the issues of digital polar power amplifier: spectral images and delay mismatch. In order to reduce the problem of spectral images, interpolation of phase and amplitude is proposed in this work. This increases the effective sampling frequency of the amplitude and phase, which helps to improve the linearity by around 10 dB. In addition, a novel calibration scheme is proposed here for the delay mismatch between phase and amplitude path in a digital polar power amplifier. The scheme significantly reduces the spectral regrowth. The scheme uses the same path for phase and amplitude delay calculation after the recombination that allows having a robust calibration. Furthermore, it can be executed during the empty transmission slots. The proposed scheme is designed in a 40 nm CMOS technology and simulated with a 64-QAM IEEE 802.11n wireless standard. The scheme achieved 7.57 dB enhancement in ACLR and 84.35% improvement in EVM for a 3.5 ns mismatch in phase and amplitude path

Ultralight (Lμ−Lτ)(L_\mu-L_\tau) vector dark matter interpretation of NANOGrav observations

The angular correlation of pulsar residuals observed by NANOGrav and other pulsar timing array (PTA) collaborations show evidence in support of the Hellings-Downs correlation expected from stochastic gravitational waves (SGW). In this paper, we offer a non-gravitational wave explanation of the observed pulsar timing correlations as caused by an ultra-light $L_{\mu} - L_{\tau}$ gauge boson dark matter (ULDM). ULDM can affect the pulsar correlations in two ways. The gravitational potential of vector ULDM gives rise to a Shapiro time-delay of the pulsar signals and a non-trivial angular correlation (as compared to the scalar ULDM case). In addition, if the pulsars have a non-zero charge of the dark matter gauge group then the electric field of the local dark matter causes an oscillation of the pulsar and a corresponding Doppler shift of the pulsar signal. We point out that pulsars carry a significant charge of muons and thus the $L_{\mu} - L_{\tau}$ vector dark matter contributes to both the Doppler oscillations and the time-delay of the pulsar signals. Our analysis shows that the NANOGrav data has a better fit to the $L_{\mu} - L_{\tau}$ ULDM scenario compared to the SGW or the SGW with Shapiro time-delay hypotheses.Comment: 10 pages, 4 figures. Comments are welcom

Examination of Procedure Safeguards Under the Indian Constitution (Article 21) and Specific Laws Like C.P.C., Bhartiya Nagarik Suraksha Sanhita, 2023 and Bhartiya Sakshya Sanhita, 2023

The Indian Constitution guarantees the right to life and personal liberty under Article 21, emphasizing that no individual shall be deprived of these rights except through the procedure established by law. This provision, interpreted expansively by the judiciary, establishes a constitutional framework for procedural safeguards that ensure fairness, reasonableness, and adherence to natural justice principles. The procedural safeguards under Article 21 are further operationalized through statutes such as the Code of Civil Procedure (C.P.C.), the Bhartiya Nagarik Suraksha Sanhita, 2023 (BNSS), and the Bhartiya Sakshya Sanhita, 2023 (BSS). These laws collectively aim to uphold individual rights while balancing the needs of an efficient justice delivery system. The C.P.C. lays down the procedural rules for civil litigation, emphasizing natural justice, equity, and fair access to courts. Provisions such as summons issuance, the opportunity for hearing, and appellate mechanisms ensure transparency and protect litigants’ rights. Recent amendments, including electronic case management and alternative dispute resolution mechanisms, demonstrate the commitment to making civil procedures efficient without compromising procedural integrity. In the domain of criminal law, the BNSS, 2023, replaces the colonial-era Criminal Procedure Code with modernized provisions that enhance procedural safeguards. Key reforms include stricter rules for arrests, judicial oversight of investigations, and robust rights for accused individuals, such as the right to be informed of charges and access to legal counsel. Victim-centric reforms, including provisions for compensation and witness protection, are significant steps towards equitable justice. The BSS, 2023, replaces the Indian Evidence Act, introducing comprehensive guidelines on evidence admissibility in the digital age. The law incorporates safeguards to ensure the authenticity of electronic evidence, protections for vulnerable witnesses, and adherence to fair trial principles. By retaining protections against self-incrimination and ensuring accused persons\u27 rights to confront evidence, the BSS aligns with constitutional mandates under Article 21. Judicial interpretations, notably in Maneka Gandhi v. Union of India (1978), have expanded Article 21’s scope, embedding due process and natural justice into India’s legal system. However, practical challenges, including judicial delays, inadequate enforcement, and resource constraints, continue to hinder procedural safeguards\u27 effectiveness. To strengthen these safeguards, systemic reforms are necessary, including capacity building for judicial officers, better technological integration in court processes, and public legal education initiatives. These measures will not only enhance procedural fairness but also contribute to timely and effective justice delivery. In conclusion, procedural safeguards under Article 21 and statutory laws such as the C.P.C., BNSS, and BSS are crucial for maintaining the rule of law and protecting individual rights. While recent legislative advancements address contemporary challenges, ensuring their effective implementation will be critical to achieving a robust and just legal system