Single axis pointing for underactuated spacecraft with a residual angular momentum

The problem of aiming a generic body-fixed axis along an inertially fixed direction is dealt with for an underactuated spacecraft in the presence of a non-zero residual angular momentum, when only two reaction wheels can exchange angular momentum with the spacecraft platform. An analytical condition for the feasibility of the desired pointing is derived first, together with a closed-form solution for the corresponding attitude with zero platform angular rate. A nonlinear controller is then developed in the framework of singular perturbation theory, enforcing a two-timescale response to the system. Convergence to the desired attitude, when the pointing direction falls within admissible limits, is then proved for rest-to-rest maneuvers and randomly generated initial tumbling conditions for a configuration representative of a small-size satellite

Carbon nanomaterials-based electrically conductive scaffolds to repair the ischaemic heart tissue

Ischaemic heart diseases are the leading causes of morbidity around the world and pose serious socio-economic burdens. Ischaemic events, such as myocardial infarction, lead to severe tissue damage and result in the formation of scar tissue. This scar tissue, being electrically inert, does not conduct electrical currents and thus generates lethal arrhythmias. The ventricle dilates with time due to asynchronous beating due to the scar, and it eventually leads to total heart failure. The current pharmacological approaches only cure heart failure symptoms without inducing tissue regeneration. Therefore, heart transplant remains the gold standard to date, but the limited organ donors and the possibility of immune rejection make this approach elusive. Cardiac tissue engineering has the potential to address this issue by engineering artificial heart tissues using 3D scaffolds cultured with cardiac stem cells. Compared with the traditional non-conductive scaffold, electroconductive scaffolds can transfer feeble electric currents among the cultured cells by acting as a "wire". This improves intercellular communication and synchronisation that otherwise is not possible using non-conductive scaffolds. This article reviews the recent advances in carbon nanomaterials-based electroconductive scaffolds, their in vitro/in vivo efficacy, and their potential to repair ischaemic heart tissue

Single nucleotide polymorphisms detected and in silico analysis of the 5' flanking sequence and exon 1 in the Bubalus bubalis leptin gene

In this study, we have sequenced the 5' flanking region and exon 1 of the leptin gene in buffalo, and have detected eight single nucleotide polymorphisms; we have made evidence, through in silico analysis, that many of them fall within putative binding sites for transcription factors. Starting from the bovine whole genome shotgun sequence, that encodes the complete sequence of the leptin gene, we had designed primers to amplify two amplicons, so to cover the 5' flanking and exon 1 of the leptin gene of 41 non related buffalos. The newly sequenced buffalo fragment was submitted to profile search for transcription factor binding sites, using the MATCH program, focusing on the areas where the single nucleotide polymorphisms had been detected. Our analysis shows that the majority of the identified single nucleotide polymorphisms fall into the core sequence of transcription factor binding sites that regulate the expression of target genes in many physiological processes within mammalian tissues. Because the leptin gene plays an important role in influencing economic traits in cattle, the novel detected single nucleotide polymorphisms might be used in association studies to assess their potential of being genetic markers for selection

Extrinsically conductive nanomaterials for cardiac tissue engineering applications

Myocardial infarction (MI) is the consequence of coronary artery thrombosis resulting in ischemia and necrosis of the myocardium. As a result, billions of contractile cardiomyocytes are lost with poor innate regeneration capability. This degenerated tissue is replaced by collagen-rich fibrotic scar tissue as the usual body response to quickly repair the injury. The non-conductive nature of this tissue results in arrhythmias and asynchronous beating leading to total heart failure in the long run due to ventricular remodelling. Traditional pharmacological and assistive device approaches have failed to meet the utmost need for tissue regeneration to repair MI injuries. Engineered heart tissues (EHTs) seem promising alternatives, but their non-conductive nature could not resolve problems such as arrhythmias and asynchronous beating for long term in-vivo applications. The ability of nanotechnology to mimic the nano-bioarchitecture of the extracellular matrix and the potential of cardiac tissue engineering to engineer heart-like tissues makes it a unique combination to develop conductive constructs. Biomaterials blended with conductive nanomaterials could yield conductive constructs (referred to as extrinsically conductive). These cell-laden conductive constructs can alleviate cardiac functions when implanted in-vivo. A succinct review of the most promising applications of nanomaterials in cardiac tissue engineering to repair MI injuries is presented with a focus on extrinsically conductive nanomaterials

Fluorescent Silver Nanoclusters Embedded in Hydrogel Matrix and Its Potential Use in Environmental Monitoring

The optical absorption and fluorescence of silver nanoclusters (AgNCs) are widely exploited in many different application fields such as sensors, bio-imaging, drug delivery, etc. In the sensor field, optical devices are highly versatile thanks to their ease of fabrication and low costs and, therefore, are optimal candidates to replace expensive apparatuses commonly used. In this study, we synthesized AgNCs in aqueous phase by photochemical synthesis using poly methacrylic acid (PMAA) as a stabilizer. Colloidal water solutions of these NCs showed a very good sensitivity to Pb(II) ions, and in order to fabricate a solid-state sensor, we introduced them in a hydrogel material formed by poly(ethylene glycol) diacrylate with a molecular weight of 700 g/mol (PEGDA700). The systems were characterized using absorption and fluorescence spectroscopy and transmission electron microscopy (TEM). Finally, the sensitivity to Pb(II) ions has been tested with the aim to use these systems as solid-state optical sensors for water quality

Fluorescent silver nanoclusters embedded in hydrogel matrix and its potential use in environmental monitoring

The optical absorption and fluorescence of silver nanoclusters (AgNCs) are widely exploited in many different application fields such as sensors, bio-imaging, drug delivery, etc. In the sensor field, optical devices are highly versatile thanks to their ease of fabrication and low costs and, therefore, are optimal candidates to replace expensive apparatuses commonly used. In this study, we synthesized AgNCs in aqueous phase by photochemical synthesis using poly methacrylic acid (PMAA) as a stabilizer. Colloidal water solutions of these NCs showed a very good sensitivity to Pb(II) ions, and in order to fabricate a solid-state sensor, we introduced them in a hydrogel material formed by poly(ethylene glycol) diacrylate with a molecular weight of 700 g/mol (PEGDA(700)). The systems were characterized using absorption and fluorescence spectroscopy and transmission electron microscopy (TEM). Finally, the sensitivity to Pb(II) ions has been tested with the aim to use these systems as solid-state optical sensors for water quality