265 research outputs found
Enhanced Channel Estimation in mm-Wave MIMO Systems Leveraging Integrated Communication and Sensing
This paper tackles the challenge of wideband MIMO channel estimation within
indoor millimeter-wave scenarios. Our proposed approach exploits the integrated
sensing and communication paradigm, where sensing information aids in channel
estimation. The key innovation consists of employing both spatial and temporal
sensing modes to significantly reduce the number of required training pilots.
Moreover, our algorithm addresses and corrects potential mismatches between
sensing and communication modes, which can arise from differing sensing and
communication propagation paths. Extensive simulations demonstrate that the
proposed method requires 4x less pilots compared to the current
state-of-the-art, marking a substantial advancement in channel estimation
efficiency
Waveform Design for OFDM-based ISAC Systems Under Resource Occupancy Constraint
Integrated Sensing and Communication (ISAC) is one of the key pillars
envisioned for 6G wireless systems. ISAC systems combine communication and
sensing functionalities over a single waveform, with full resource sharing. In
particular, waveform design for legacy Orthogonal Frequency Division
Multiplexing (OFDM) systems consists of a suitable time-frequency resource
allocation policy balancing between communication and sensing performance. Over
time and/or frequency, having unused resources leads to an ambiguity function
with high sidelobes that significantly affect the performance of ISAC for OFDM
waveforms. This paper proposes an OFDM-based ISAC waveform design that takes
into account communication and resource occupancy constraints. The proposed
method minimizes the Cram\'er-Rao Bound (CRB) on delay and Doppler estimation
for two closely spaced targets. Moreover, the paper addresses the
under-sampling issue by interpolating the estimated sensing channel based on
matrix completion via Schatten -norm approximation. Numerical results show
that the proposed waveform outperforms the state-of-the-art methods.Comment: 6 page
Advanced Tri-Sectoral Multi-User Millimeter-Wave Smart Repeater
Smart Repeaters (SR) can potentially enhance the coverage in Millimeter-wave
(mmWave) wireless communications. However, the angular coverage of the existing
two-panel SR is too limited to make the SR a truly cost-effective mmWave range
extender. This paper proposes the usage of a tri-sectoral Advanced SR (ASR) to
extend the angular coverage with respect to conventional SR. We propose a
multi-user precoder optimization for ASR in a downlink multi-carrier
communication system to maximize the number of served User Equipments (UEs)
while guaranteeing constraints on per-UE rate and time-frequency resources.
Numerical results show the benefits of the ASR against conventional SR in terms
of both cumulative spectral efficiency and number of served UEs (both improved
by an average factor 2), varying the system parameters
How the chemical features of molecules may have addressed the settlement of metabolic steps
Introduction: While the evolutionary adaptation of enzymes to their own substrates is a well assessed and rationalized field, how molecules have been originally selected in order to initiate and assemble convenient metabolic pathways is a fascinating, but still debated argument. Objectives: Aim of the present study is to give a rationale for the preferential selection of specific molecules to generate metabolic pathways. Methods: The comparison of structural features of molecules, through an inductive methodological approach, offer a reading key to cautiously propose a determining factor for their metabolic recruitment. Results: Starting with some commonplaces occurring in the structural representation of relevant carbohydrates, such as glucose, fructose and ribose, arguments are presented in associating stable structural determinants of these molecules and their peculiar occurrence in metabolic pathways. Conclusions: Among other possible factors, the reliability of the structural asset of a molecule may be relevant or its selection among structurally and, a priori, functionally similar molecules
Thiol oxidase ability of copper ion is specifically retained upon chelation by aldose reductase
Bovine lens aldose reductase is susceptible to a copper-mediated oxidation, leading to the generation of a disulfide bridge with the concomitant incorporation of two equivalents of the metal and inactivation of the enzyme. The metal complexed by the protein remains redox active, being able to catalyse the oxidation of different physiological thiol compounds. The thiol oxidase activity displayed by the enzymatic form carrying one equivalent of copper ion (Cu1-AR) has been characterized. The efficacy of Cu1-AR in catalysing thiol oxidation is essentially comparable to the free copper in terms of both thiol concentration and pH effect. On the contrary, the two catalysts are differently affected by temperature. The specificity of the AR-bound copper towards thiols is highlighted with Cu1-AR being completely ineffective in promoting the oxidation of both low-density lipoprotein and ascorbic acid
Apparent cooperativity and apparent hyperbolic behavior of enzyme mixtures acting on the same substrate
It is well known that a negative cooperative behavior displayed by a monomeric enzyme may be associated with the simultaneous presence of two enzymes acting on the same substrate. In this paper, emphasis is given to the effect exerted by a rapid equilibrium between the enzyme forms in leading to a hyperbolic behavior, thus masking the presence of multiple enzyme forms
Models of enzyme inhibition and apparent dissociation constants from kinetic analysis to study the differential inhibition of aldose reductase
In order to explain the negative slope of K-app(M)/(app)k(cat) versus inhibitor concentration observed in the study of epigallocatechin gallate acting as an inhibitor of aldose reductase, a kinetic analysis was performed to rationalise the phenomenon. Classical and non-classical models of complete and incomplete enzyme inhibition were devised and analysed to obtain rate equations suitable for the interpretation of experimental data. The results obtained from the different approaches were discussed in terms of the meaning of the emerging kinetic constants. A decrease of K-app(M)/(app)k(cat) versus the inhibitor concentration was revealed to be a valuable indication of the occurrence of an incomplete inhibition. This indication, which is univocal in the case of an uncompetitive inhibition, may be especially useful when the residual activity resulting from inhibition is rather low
Cysteinyl-glycine in the control of glutathione homeostasis in bovine lenses
PURPOSE:
To define a possible metabolic and/or signaling role for Cys-Gly in glutathione homeostasis in bovine eye lenses.
METHODS:
Bovine lenses were cultured up to 24 h in a medium containing 0.5 mM reduced glutathione (GSH) under different conditions. The intracellular and the extracellular contents of thiol compounds were evaluated using a free zone capillary electrophoresis method.
RESULTS:
Culture of lenses in the presence of GSH and the gamma-glutamyl transferase inhibitor serine-borate demonstrated a 1.5 fold increase in the level of extra-lenticular glutathione with respect to the initial value. Cys-Gly exogenously added impaired the extra-lenticular accumulation of glutathione. Both cysteine and gamma-Glu-Cys were ineffective in reducing extra-lenticular glutathione accumulation. In all conditions no differences in reduced and total intra-lenticular glutathione levels were observed.
CONCLUSIONS:
The impairment of Cys-Gly generation correlated with inhibition of gamma-glutamyl transferase by serine/borate, resulting in high extra-lenticular concentration of glutathione effluxed from the bovine lens. The possibility that Cys-Gly may intervene either in the replenishment processes for cysteine in the GSH biosynthetic step or in the function of the efflux GSH-transporters is considered
Modulation of aldose reductase activity by aldose hemiacetals
Glucose is considered as one of the main sources of cell damage related to aldose reductase (AR) action in hyperglycemic conditions and a worldwide effort is posed in searching for specific inhibitors of the enzyme. This AR substrate has often been reported as generating non-hyperbolic kinetics, mimicking a negative cooperative behavior. This feature was explained by the simultaneous action of two enzyme forms acting on the same substrate
Edible vegetables as a source of aldose reductase differential inhibitors
The hyperactivity of aldose reductase (AR) on glucose in diabetic conditions or on glutathionyl-hydroxynonenal in oxidative stress conditions, the source of cell damage and inflammation, appear to be balanced by the detoxifying action exerted by the enzyme. This detoxification acts on cytotoxic hydrophobic aldehydes deriving from membrane peroxidative processes. This may contribute to the failure in drug development for humans to favorably intervene in diabetic complications and inflammation, despite the specificity and high efficiency of several available aldose reductase inhibitors. This paper presents additional features to a previously proposed approach, on inhibiting the enzyme through molecules able to preferentially inhibit the enzyme depending on the substrate the enzyme is working on. These differential inhibitors (ARDIs) should act on glucose reduction catalyzed by AR without little or no effect on the reduction of alkenals or alkanals. The reasons why AR may be an eligible enzyme for differential inhibition are considered. These mainly refer to the evidence that, although AR is an unspecific enzyme that recognizes different substrates such as aldoses and hydrophobic aldehydes, it nevertheless displays a certain degree of specificity among substrates of the same class. After screening on edible vegetables, indications of the presence of molecules potentially acting as ARDIs are reported
- …