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In recent years, considerable evidence has accrued indicating that brain function can be flexibly reconfigured on the fly: many brain areas are capable of carrying out a variety of distinct functions and are able to switch between those functions in a context-sensitive, dynamic fashion. Some evidence has also emerged that ongoing brain activity, the ceaseless background brain dynamics, may be implicated in setting and controlling these flexible functions as well as attentional gain. A crucial link between them is dynamics. Here we review both the accumulating evidence as well as propose a theoretical outline of dynamical mechanisms for functional self-reconfiguration of neural networks, including reconfiguration of logic function, reconfiguration of information routing, and poising at critical points to switch dynamics.

In the context of the rural electrification challenge, sharing-based nanogrids represent an innovative approach for affordable and sustainable electricity. The peer-to-peer topology of these nanogrids is targeted at organic growth and thus requires real time monitoring and optimization. A data analysis tool has been developed, aiming at achieving an efficient power flow and real time optimization of generation, storage, load and distribution capacities. This paper elaborates the core algorithms of the network topology optimization and provides first results based on data from a pilot nanogrid in Bangladesh.

While de novo donor-specific HLA antibodies (dnDSAs) have a detrimental impact on kidney graft outcome, the clinical significance of de novo non donor-specific antibodies (dnNDSAs) is more controversial. We retrospectively evaluated for Ab development and characteristics of dnNDSAs serially collected post-transplant sera and, when available, graft biopsy eluates, from 144 non-sensitized, primary pediatric kidney recipients, consecutively transplanted at a single center between 2003 and 2017, using HLA class I and class II single-antigen flow-bead assays (SAB). The results were compared with clinical-pathologic data from HLA antibody negative and HLA dnDSA-positive patients. Forty-five out of 144 patients developed dnNDSAs (31%). Among the dnNDSA-positive patients, 86% displayed one or more class I/II antibodies recognizing antigens included in the CREG/shared epitope groups that also comprise the mismatched donor HLA antigens. Despite potential pathogenicity, as suggested by their occasional presence within the graft, dnNDSAs displayed significantly lower MFI, and limited complement binding and graft homing properties, when compared with dnDSAs. In parallel, the graft survival probability was significantly lower in patients with dnDSA than in those with dnNDSA or without HLA antibodies (p 0.005). Indeed, the dnNDSA-positive patients remaining dnDSA-negative throughout the posttransplant period did not develop clinical antibody mediated rejection and graft loss, and maintained good graft function at a median follow-up of 9 years. The biological characteristics of dnNDSAs may account for the low graft damaging capability when compared to dnDSAs.

Alloantibody-mediated graft injury is a major cause of kidney dysfunction and loss. The complement-binding ability of de novo donor-specific antibodies (dnDSAs) has been suggested as a prognostic tool to stratify patients for clinical risk. In this study, we analyzed posttransplant kinetics of complement-fixing dnDSAs and their role in antibody-mediated rejection development and graft loss. A total of 114 pediatric nonsensitized recipients of first kidney allograft were periodically monitored for dnDSAs using flow bead assays, followed by C3d and C1q assay in case of positivity. Overall, 39 patients developed dnDSAs, which were C1q(+) and C3d(+) in 25 and nine patients, respectively. At follow-up, progressive acquisition over time of dnDSA C1q and C3d binding ability, within the same antigenic specificity, was observed, paralleled by an increase in mean fluorescence intensity that correlated with clinical outcome. C3d-fixing dnDSAs were better fit to stratify graft loss risk when the different dnDSA categories were evaluated in combined models because the 10-year graft survival probability was lower in patients with C3d-binding dnDSA than in those without dnDSAs or with C1q(+) /C3d(-) or non-complement-binding dnDSAs (40% vs. 94%, 100%, and 100%, respectively). Based on the kinetics profile, we favor dnDSA removal or modulation at first confirmed positivity, with treatment intensification guided by dnDSA biological characteristics.

Background It is still unclear what might be the best management of people living with HIV (PLWHIV) with low level viremia (LLV) despite being on antiretroviral treatment (ART). Objectives Aim of our study is to describe the clinical management of PLWHIV with LLV followed in a large cohort. Study design Retrospective cohort study. Results We included 1607 adult patients over a three-year period (2015–2017). Follow up continued until June, 30th 2019 or last available visit. We observed a low incidence of LLV (0.9 % in 2015, 0.7 % in 2016 and 0.4 % in 2017), with a total of 21 patients with persistent LLV (pLLV), i.e. two consecutive HIV-RNA determinations of 50–500 copies/ml after at least 4 months of viral suppression. Among them, 12 had low compliance to treatment. Genotype resistance test (GRT) was performed in 14 patients and demonstrated at least one resistance mutation in 85.7 %. We described three categories of patients with pLLV: i) those whose ART regimen was not adequate based on GRT; ii) those with presumed suboptimal drug exposure, consequence of low adherence and/or drug-drug interactions and iii) those in which pLLV remained unexplained. For the first two categories, optimization or intensification of ART regimen led to viral suppression in >80 % of patients. We observed only 2 (9.5 %) virological failures and 1 (4.8 %) persistence of LLV in patients who did not switch ART. Conclusions In our cohort, the rate of LLV showed a decline in most recent years. Adherence and previous GRT should be carefully considered with the aim of further reducing the phenomenon.

Large scale CI calculations of frequency-dependent dipole polarizabilities (FDPs) of ground state BH at the experimental distance of R = 2.329a0 have been performed using two sets of contracted GTO functions involving up to 316 × 106 symmetry-adapted Slater determinants, comparing recently developed interpolation and variational techniques. Final calculation of BH–BH dispersion coefficients was done using the larger basis set of 268 AOs in the frozen-core FCI approximation and the lower bounds resulting from the variational approach.

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti-HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor-specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical-pathologic data. At 4.3-year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non-DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA-DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody-mediated rejection (AMR), and four C4d-negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1-year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab-negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.

The solution of the asymptotic quantum mechanical differential equations in the neighbourhood of singular points is suggested to overcome some complexities occurring with the technique of the indicial equations. After separation of the variables, the differential equations are solved in their asymptotic regions, the general regular solutions in the whole interval being then found by replacing integration constants by functions of the variables and finding the differential equations determining these functions. The resulting differential equations are now free from singularities and can be solved by the usual series expansion, giving simple polynomial solutions for the harmonic oscillator and the hydrogen atom and more complicated solutions for H 2 + .

Quantum corrections in the moderately low-temperature regime to the interaction potential energy of two permanent molecular dipoles are evaluated through the Wigner–Uhlenbeck–Gropper (WUG) semiclassical expansion of the density matrix, whose leading term is proportional to ℏ 2 , the dipoles being assumed in oscillatory motion around their position of minimum energy. Application of the resulting formulae to the ground states of a few heteropolar diatomic molecules and radicals shows that the quantum correction is not negligible, being particularly relevant for BH and OH.

In the elementary Huckel theory of ground state HF at its simplest valence level the two unknown parameters ∣αp − αh∣ and ∣β∣ can be determined in terms of experimental bond dissociation energy and electric dipole moment. If some sp hybridization is admitted on F in a bond orbital approximation, optimization of the resulting Huckel energy against the hybridization parameter ω using 1-term SCF/STOs shows that little hybridization (ω ≈ 8°) gives a 3% increase in the bond energy parameter ∣β∣ and a 14% reduction in the value of the formal charges ∣δ∣ on the interacting atoms.

Huckel transformation theory is applied to the study of the hybridization problem in ground state NH 3 . Under assumptions similar to those recently introduced for H 2 O, minimization of the model Huckel energy at the valence level yields a trigonometric relation between bond angle and hybridization parameter showing that hybridization opens the interbond angle beyond 90°. A further orthogonal transformation mixing in AOs belonging to A 1 and E symmetry yields four orthogonal sp 3 hybrids of C 3v symmetry on nitrogen that can be engaged in the axially symmetric lone pair and three equivalent straight N–H bonds making the experimental interbond angle.

In a previous paper on the Keesom effect, we presented a procedure for the evaluation of the average potential energy of interaction between two dipoles of strength μ a distance R apart in the limit of small temperature T . The resulting expansion in terms of the dimensionless T -dependent parameter a = − μ 2 / R 3 kT was then proved by us to be an asymptotic one. Here we reformulate our method in a simplified form, extending it to include the quantum effects which must be taken into account in the low-temperature regime. The resulting formulae show explicitly the transition from the quantum regime to the classical one as a function of temperature.

An orthogonal transformation of the oxygen valence AOs belonging to A 1 symmetry to an ω -hybridized sp basis set allows for useful simplifications reducing Huckel transformed matrix for ground state H 2 O to nearly block-diagonal form. Neglecting delocalization of the hybrid lone pair into the bond, minimization of the resulting Huckel energy shows that for ω ≠ 0 the interbond angle opens beyond 90°. A further orthogonal transformation involving the B 2 y AO yields three orthogonal sp 2 hybrids of C 2v symmetry on oxygen which can be engaged in two equivalent straight O–H bonds making the experimental interbond angle and locally minimizing the Huckel energy of the valence electron configuration.

A self-consistent theory of the linear response previously developed by one of us is applied to the dipole–dipole dispersion interaction of two ground state H atoms in the united atom (He) limit, using a Sellmeier representation of the polarizability in terms of pseudostates. Numerical calculations show that a truncated 12-term expansion out of the N = 22 H(1s) dipole pseudospectrum built from STOs with orbital exponent c = 0.985 gives a result exceeding by no more than 5% the variational result for the He dispersion energy.

A recently proposed technique for interpolating numerical evaluations performed on frequency-dependent polarizabilities and obtaining analytically the related dispersion constants is improved in order to deal with larger sets of available data.

T-dependent long-range Keesom coefficients are evaluated up to the R-10 term for small values of the dimensionless parameter vertical bar a(ll ')vertical bar For large values of vertical bar all 'vertical bar, I corrections must be introduced mostly for the dipole-dipole term, the correct values of Q being best obtained from a recently derived asymptotic formula. The corresponding attractive energies are the isotropic electrostatic contributions to the interaction energy and are temperature-dependent. Comparison with long-range induction and dispersion energy results for some simple polar axially symmetric molecules in the gas phase shows that at R = 10a(0) and T = 293 K the electrostatic dipole-dipole component is dominant for vertical bar a(11)vertical bar > 0.5. For centrosymmetric molecules the corresponding electrostatic contribution is usually negligible with respect to dispersion.

Explicit analytical formulae are presented for the exact R n -expansion of the short-range electronic interaction energy for ground state H 2 + up to n = 10. The corresponding calculated values for small values of the internuclear distance are in excellent agreement with Peek’s accurate results up to R = 0.30 a 0 .

It is shown in this Letter that the erroneous bond length resulting for the bound 1 Σ u + state of H 2 described by the ionic valence bond structure over the minimum set of 1s STO functions is corrected by the variational inclusion with a substantial weight of the singly excited covalent structures involving 2s and 2pσ STOs onto each H atom. The corresponding value for the molecular energy resulting from the complete optimization of the orbital exponents gives now over 96% of the accurate Kolos–Wolniewicz results.

Frozen-core full-CI calculations of frequency-dependent dipole polarizabilities (FDPs) of ground state BeH 2 at the experimental distance of R = 2.506 a 0 have been performed using an extended set of 208 contracted GTO functions [9s9p5d3f] on Be and [9s8p6d] on H involving about 58 × 10 6 symmetry-adapted Slater determinants. The Casimir–Polder integral was then evaluated analytically using eight optimized imaginary frequencies chosen according to a recently developed interpolation technique which allows for the evaluation of the three dipole dispersion constants for the BeH 2 –BeH 2 homodimer, from which isotropic C 6 and anisotropy γ 6 coefficients are derived for the first time.

Making the usual assumptions typical of elementary Huckel theory including overlap it is shown that the Huckel energy of the two-electron bond is minimized for orbitals having maximum overlap, which yields maximum strength for the straight bond. Analysis of the bond energy for the general A–B bond shows for the molecular orbital description a more complicated dependence on the one-electron exchange-overlap densities of A and B than that recently derived by us in a corresponding valence bond treatment.

Revisitation of the Heitler–London theory for H2 shows that the exchange-overlap component of the bond energy has a strength which is maximum at the bond length. Making the usual assumptions typical of elementary Huckel theory including overlap it is similarly found that in the valence bond description of the chemical bond covalent bonding is strongest for atomic orbitals maximizing the strength of the complete exchange-overlap component of the bond energy.

A two-state model of van der Waals (VdW) interactions is presented which completes the elementary description of the interactions occurring between atoms and molecules. A weak VdW bond is formed between closed-shell atoms or molecules as soon as the small Pauli repulsion is offset in long range by attractive VdW interactions. These are distortion and dispersion interactions, related to the electric properties of the interacting molecules, and described as small second-order effects in terms of long range interaction integrals β s. The explicit forms of these β s are derived from classical electrostatics for atom–atom, atom–linear molecule dispersion, and atom–linear molecule induction. Comparison between C 6 dispersion and induction coefficients for simple homodimers shows that dispersion is, in general, the most important attractive VdW interaction in long range.

Effector CD4+ T cells rapidly activate high-level cytokine expression following TCR stimulation. Consistent with accelerated protein production in these cells, global mRNA profiles revealed that, after cytokines, the most impressive cluster of activated genes encode rRNA-maturation factors. Activation of these genes was ERK-MAPK dependent, accompanied by increased rRNA transcription and faster maturation kinetics, and much greater in effector CD4+ T cells than in naive cells. Ribosomal protein subunit (RPS) synthesis was also ERK-MAPK dependent and increased to match rRNA production, but without evident increase in RPS mRNA. Instead, stimulation promoted polysome loading of RPS mRNA via cis-acting, 5′-terminal oligopyrimidines. These results demonstrate how, in response to extracellular signals, effector CD4+ T cells coordinately increase multiple ribosomal components to accommodate burgeoning cytokine production.

The simple Huckel model of the chemical bond, proposed earlier and applied mostly to homonuclear diatomics, is extended to the case of the heteropolar bond. The filling of electrons into the MO levels has now more possibilities than in the previous homonuclear case. For orthogonal AOs, the fundamental quantities entering the model, the atomic energy difference α2−α1 and the bond integral |β| can be determined using the experimental values of the atomization energy De and the electric dipole moment μ. The results obtained for the two-electron σ-bonds occurring in the first-row series of ground state diatomic hydrides are analyzed and shortly discussed.

Fluctuation theory techniques are used to evaluate short-range interactions in ground state H 2 + by calculating in a direct way small energy differences taken with respect to the ground state of the united atom He + . Appropriate coordinate transformation allows to obtain inner and outer Hermitean eigenvalue equations, which are then solved perturbatively in positive powers of the internuclear distance R choosing He + as unperturbed problem. The separation constants are deduced from the regularity conditions on the functions. Next, the function endowed with the right symmetry is constructed by solving an integral equation in a perturbative way. A second-order approximation gives short-range interaction coefficients which are exact up to R 5 .

An elementary technique has been developed to intercept available values of a given atomic or molecular multipole dynamic polarizability through an expression providing a faithful representation for its dependence on the imaginary frequency. The explicitation of the implied interpolative parameters is obtained by imposing that the available data ought to be exactly intercepted. Numerical tests concerning a ground state hydrogen atom have confirmed the reliability of such interpolative procedure for extracting continuous trends from some initial estimates performed on multipole polarizabilities and for evaluating dispersion constants.

Ordinary LCAO-MO theory allows for the ab-initio definition of α and β parameters occurring in the Huckel theory including overlap of simple σ homonuclear systems. One- and two-electron terms not included in Huckel theory are explicitly considered. When such correction terms are neglected in the very spirit of Huckel theory, simple calculation in the hydrogenic approximation for the ground states of H2+, H2, He2+, He2 at the corresponding bond lengths shows semiquantitative agreement with experimental or accurate theoretical results for the bond energies, providing a simple and clear physical picture of the nature of the chemical bond.

Small well-shaped basis sets have been used to perform highly accurate variational-perturbative evaluations of dynamic (frequency-dependent) multipole polarizabilities for a hydrogen atom in its ground state. Their structure has been suggested by the ab initio polynomial power expansion we have recently developed to get correspondingly exact results within a finite range covering the region of low frequencies. The frequency-dependent coefficients of the optimized linear combinations of the excited pseudostate orbitals were obtained by diagonalizing the representative matrix of the excitation operator from the ground state. High levels of accuracy have been observed over a set of frequencies now covering the complete real and imaginary ranges.