Bianchi I effective dynamics in Quantum Reduced Loop Gravity

The effective quantum dynamics of Bianchi I spacetime is addressed within the statistical regularization scheme in Quantum Reduced Loop Gravity. The case of a minimally coupled massless scalar field is studied and compared with the effective $\bar{\mu}-$Loop Quantum Cosmology. The dynamics provided by the two approaches match in the semiclassical limit but differ significantly after the bounces. Analytical and numerical inspections show that energy density, expansion scalar and shear are bounded also in Quantum Reduced Loop Gravity and the classical singularity is resolved for generic initial conditions in all spatial directions.Comment: 19 pages, 23 figures, 1 tabl

The Streptomyces coelicolor small ORF trpM stimulates growth and morphological development and exerts opposite effects on actinorhodin and calcium-dependent antibiotic production

In actinomycetes, antibiotic production is often associated with a morpho-physiological differentiation program that is regulated by complex molecular and metabolic networks. Many aspects of these regulatory circuits have been already elucidated and many others still deserve further investigations. In this regard, the possible role of many small open reading frames (smORFs) in actinomycete morpho-physiological differentiation is still elusive. In Streptomyces coelicolor, inactivation of the smORF trpM (SCO2038) – whose product modulates L-tryptophan biosynthesis – impairs production of antibiotics and morphological differentiation. Indeed, it was demonstrated that TrpM is able to interact with PepA (SCO2179), a putative cytosol aminopeptidase playing a key role in antibiotic production and sporulation. In this work, a S. coelicolor trpM knock-in (Sco-trpMKI) mutant strain was generated by cloning trpM into overexpressing vector to further investigate the role of trpM in actinomycete growth and morpho-physiological differentiation. Results highlighted that trpM: (i) stimulates growth and actinorhodin (ACT) production; (ii) decreases calcium-dependent antibiotic (CDA) production; (iii) has no effect on undecylprodigiosin production. Metabolic pathways influenced by trpM knock- in were investigated by combining two-difference in gel electrophoresis/nanoliquid chromatography coupled to electrospray linear ion trap tandem mass spectrometry (2D- DIGE/nanoLC-ESI-LIT-MS/MS) and by LC-ESI-MS/MS procedures, respectively. These analyses demonstrated that over-expression of trpM causes an over-representation of factors involved in protein synthesis and nucleotide metabolism as well as a down-representation of proteins involved in central carbon and amino acid metabolism. At the metabolic level, this corresponded to a differential accumulation pattern of different amino acids – including aromatic ones but tryptophan – and central carbon intermediates. PepA was also down-represented in Sco-trpMKI. The latter was produced as recombinant His-tagged protein and was originally proven having the predicted aminopeptidase activity. Altogether, these results highlight the stimulatory effect of trpM in S. coelicolor growth and ACT biosynthesis, which are elicited through the modulation of various metabolic pathways and PepA representation, further confirming the complexity of regulatory networks that control antibiotic production in actinomycetes

Erratum: Lipase-catalyzed regioselective acylation of resorcin[4]arenes (Journal of Molecular Catalysis B: Enzymatic (2002) 16 (24-247) PII: S1381117701000686)

10Immobilized lipase from Mucor miehei (RML) catalyzed the regioselective acylation of the C-2 side-chain of the C-alkyl resorcin[4]arene tetra-alcohol 1 in the 1,2-alternate form in organic solvents using vinyl acetate as acylating reagent. The influence of reaction parameters and solvent choice were also studied. Docking simulations allowed the determination of the binding geometry of 1, revealing the importance of Trp88 residue in stabilizing the Michaelis–Menten complex between enzyme and substrate.reservedmixedBotta, Bruno; Zappia, Giovanni; Tafi, Andrea; Botta, Maurizio; Manetti, Fabrizio; Cernia, Enrico; Milana, Giuliana; Palocci, Cleofe; Soro, Simonetta; Delle Monache, GiulianoBotta, Bruno; Zappia, Giovanni; Tafi, Andrea; Botta, Maurizio; Manetti, Fabrizio; Cernia, Enrico; Milana, Giuliana; Palocci, Cleofe; Soro, Simonetta; Delle Monache, Giulian

Wheeled Mobile Robots: State of the Art Overview and Kinematic Comparison Among Three Omnidirectional Locomotion Strategies

In the last decades, mobile robotics has become a very interesting research topic in the feld of robotics, mainly because of population ageing and the recent pandemic emergency caused by Covid-19. Against this context, the paper presents an overview on wheeled mobile robot (WMR), which have a central role in nowadays scenario. In particular, the paper describes the most commonly adopted locomotion strategies, perception systems, control architectures and navigation approaches. After having analyzed the state of the art, this paper focuses on the kinematics of three omnidirectional platforms: a four mecanum wheels robot (4WD), a three omni wheel platform (3WD) and a two swerve-drive system (2SWD). Through a dimensionless approach, these three platforms are compared to understand how their mobility is afected by the wheel speed limitations that are present in every practical application. This original comparison has not been already presented by the literature and it can be used to improve our understanding of the kinematics of these mobile robots and to guide the selection of the most appropriate locomotion system according to the specifc application

Design and Prototyping of an Interchangeable and Underactuated Tool for Automatic Harvesting

In the field of precision agriculture, the automation of sampling and harvesting operations plays a central role to expand the possible application scenarios. Within this context, this work presents the design and prototyping of a novel underactuated tool for the harvesting of autonomous grapevines. The device is conceived to be one of several tools that could be automatically grasped by a robotic manipulator. As a use case, the presented tool is customized for the gripper of the robotic arm mounted on the rover Agri.Q, a service robot conceived for agriculture automation, but it can be easily adapted to other robotic arm grippers. In this work, first, the requirements for such a device are defined, then the functional design is presented, and a dimensionless analysis is performed to guide the dimensioning of the device. Later, the executive design is carried out, while the results of a preliminary experimental validation test are illustrated at the end of the paper

Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

Cross-relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than 1 order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation rate-matrix approach. The calculations show that the Solomon dependence of the paramagnetic relaxation rates on the metal–proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal and thus can cause sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the paramagnetic Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at magnetic resonance imaging (MRI) magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons

A preliminary synthesis of a light and compact wearable cable-driven parallel robot for wrist joint rehabilitation

Robot-assisted rehabilitation has proven to be effective in clinical practice, not only because of its ability to perform repetitive and intensive rehabilitation therapy but also because its rehabilitation outcome is not limited by the lack of experienced therapists or their fatigue due to long and repetitive rehabilitation sessions. Several robotic solutions have been proposed over time, but rarely have these solutions been successful, in particular due to the excessive bulk, discomfort, and joints alignment of the robotic solution. This paper lays the foundation for a preliminary synthesis of a wearable cable-driven parallel robot for wrist joint rehabilitation. Specifically, the synthesis focuses on defining an ad hoc geometric efficiency index to maximise the effective force required to achieve flexion-extension, radial-ulnar deviation and pronation-supination movements with the lowest possible cable tension. To consider lightness and wearability, the results of the synthesis are weighted to obtain a light and compact system that will be developed