Manganese Sulfide (MnS) Nanocrystals: Synthesis, Properties, and Applications

Manganese(II) sulfide (MnS) is an interesting material for both fundamental and applicative research, especially when its bulk properties are modulated by reducing the size into the nanometric region (< 100 nm). Due to its polymorphism, MnS is an attractive material to develop synthetic strategies for polymorphism control. We have reviewed the literature concerning MnS nanosystems having at least one dimension smaller than 100 nm. Successful synthetic techniques for the preparation of zero- and one-dimensional MnS nanosystems (either homogeneous and heterogeneous) with size, shape, and polymorphism control are presented with emphasis on solvothermal techniques and on studies devoted to understanding the growth mechanism and the polymorphism. Properties and applications are collected in three broad areas corresponding to nanosize MnS used as an optical, electric, and magnetic material. MnS has attracting properties such as its large bandgap, which makes it promising for emission in the ultraviolet region. The magnetic properties have also arisen attention since MnS is antiferromagnetic at low temperature and (super)paramagnetic at room temperature. Finally, the layered structure of the hexagonal polymorph is responsible for the good performance of nanosize MnS as a lithium-ion battery electrode or supercapacitor material since the insertion/exchange of small ions is easy

Can you hear the Planck mass?

For the Laplacian of an n-Riemannian manifold X, the Weyl law states that the k-th eigenvalue is asymptotically proportional to (k/V)2/n, where V is the volume of X. We show that this result can be derived via physical considerations by demanding that the gravitational potential for a compactification on X behaves in the expected (4+n)-dimensional way at short distances. In simple product compactifications, when particle motion on X is ergodic, for large k the eigenfunctions oscillate around a constant, and the argument is relatively straightforward. The Weyl law thus allows to reconstruct the four-dimensional Planck mass from the asymptotics of the masses of the spin 2 Kaluza-Klein modes. For warped compactifications, a puzzle appears: the Weyl law still depends on the ordinary volume V, while the Planck mass famously depends on a weighted volume obtained as an integral of the warping function. We resolve this tension by arguing that in the ergodic case the eigenfunctions oscillate now around a power of the warping function rather than around a constant, a property that we call weighted quantum ergodicity. This has implications for the problem of gravity localization, which we discuss. We show that for spaces with Dp-brane singularities the spectrum is discrete only for p = 6, 7, 8, and for these cases we rigorously prove the Weyl law by applying modern techniques from RCD theory

Harmonic functions and gravity localization

In models with extra dimensions, matter particles can be easily localized to a 'brane world', but gravitational attraction tends to spread out in the extra dimensions unless they are small. Strong warping gradients can help localize gravity closer to the brane. In this note we give a mathematically rigorous proof that the internal wave-function of the massless graviton is constant as an eigenfunction of the weighted Laplacian, and hence is a power of the warping as a bound state in an analogue Schr\"odinger potential. This holds even in presence of singularities induced by thin branes. We also reassess the status of AdS vacuum solutions where the graviton is massive. We prove a bound on scale separation for such models, as an application of our recent results on KK masses. We also use them to estimate the scale at which gravity is localized, without having to compute the spectrum explicitly. For example, we point out that localization can be obtained at least up to the cosmological scale in string/M-theory solutions with infinite-volume Riemann surfaces; and in a known class of N = 4 models, when the number of NS5- and D5-branes is roughly equal.Comment: 43 pages, 2 figure

Multi-Head Adapter Routing for Data-Efficient Fine-Tuning

Parameter-efficient fine-tuning (PEFT) methods can adapt large language models to downstream tasks by training a small amount of newly added parameters. In multi-task settings, PEFT adapters typically train on each task independently, inhibiting transfer across tasks, or on the concatenation of all tasks, which can lead to negative interference. To address this, Polytropon (Ponti et al.) jointly learns an inventory of PEFT adapters and a routing function to share variable-size sets of adapters across tasks. Subsequently, adapters can be re-combined and fine-tuned on novel tasks even with limited data. In this paper, we investigate to what extent the ability to control which adapters are active for each task leads to sample-efficient generalization. Thus, we propose less expressive variants where we perform weighted averaging of the adapters before few-shot adaptation (Poly-mu) instead of learning a routing function. Moreover, we introduce more expressive variants where finer-grained task-adapter allocation is learned through a multi-head routing function (Poly-S). We test these variants on three separate benchmarks for multi-task learning. We find that Poly-S achieves gains on all three (up to 5.3 points on average) over strong baselines, while incurring a negligible additional cost in parameter count. In particular, we find that instruction tuning, where models are fully fine-tuned on natural language instructions for each task, is inferior to modular methods such as Polytropon and our proposed variants.Comment: Preprin

Substituent-Guided Cluster Nuclearity for Tetranuclear Iron(III) Compounds with Flat {Fe4(μ3-O)2} Butterfly Core

The tetranuclear iron(III) compounds [Fe4(μ3-O)2(μ-LZ)4] (1–3) were obtained by reaction of FeCl3 with the shortened salen-type N2O2 tetradentate Schiff bases N,N’-bis(salicylidene)-o-Z-phenylmethanediamine H2LZ (Z = NO2, Cl and OMe, respectively), where the one-carbon bridge between the two iminic nitrogen donor atoms guide preferentially to the formation of oligonuclear species, and the ortho position of the substituent Z on the central phenyl ring selectively drives towards Fe4 bis-oxido clusters. All compounds show a flat almost-symmetric butterfly-like conformation of the {Fe4(μ3-O)2} core, surrounded by the four Schiff base ligands, as depicted by both the X-ray molecular structures of 1 and 2 and the optimized geometries of all derivatives as obtained by UM06/6-311G(d) DFT calculations. The strength of the antiferromagnetic exchange coupling constants between the iron(III) ions varies among the three derivatives, despite their magnetic cores remain structurally almost unvaried, as well as the coordination of the metal ions, with a distorted octahedral environment for the two-body iron ions, Feb, and a pentacoordination with trigonal bipyramidal geometry for the two-wing iron ions, Few. The different magnetic behavior within the series of examined compounds may be ascribed to the influence of the electronic features of Z on the electron density distribution (EDD) of the central {Fe4(μ3-O)2} core, substantiated by a Quantum Theory of Atoms In Molecules (QTAIM) topological analysis of the EDD, as obtained by UM06 calculations 1–3

Opadanje stoka školjkaša Ruditapes philippinarum u uvalama sjevernog Jadrana:anketa o ekološkim i društveno-ekonomskim aspektima

The Manila clam, Ruditapes philippinarum, introduced in the Venice lagoons in 1983 and rapidly spread to the nearby coastal lagoons represents one of the most important commercially- exploited resources of this area. Abundance, size-class and biomass distribution of the wild population living in the Pialassa Baiona lagoon were assessed and related to the hydrological and sediment characteristics. Despite the lagoon being affected by eutrophication, chemical and thermal pollution, the clams were harvested by about thirty professional fishermen until 2003. The commercially available stock was estimated at 36.8 10 3 kg in July 2002, 29.3 10 3 kg in April 2003, and 10.3 10 3 kg in October 2003. Stock estimations and observed mortality were in good accordance with the fishermen data. The decline of the available stock could be due to both overfishing and the extraordinary summer heat wave occurred in 2003, which may have reduced larval recruitment and increased the mortality. Overall, the juvenile recruitment appeared insufficient to annually restore the natural stock. Although the national and regional high relevance of clams market, local harvesting of wild populations appeared marginal and inadequate to support a remunerative commercial activity, due to the variability and unpredictability of the annual yield and the lack of a sustainable management based on a production chain’s approach.Školjkaš Ruditapes philippinarum, zabilježena u Venecijanskoj laguni 1983. godine gdje se brzo proširila i na obližnje obalne lagune te predstavlja jedan od najvažnijih komercijalno iskorištenih resursa ovog područja. U laguni Pialassa Baiona procjenjene su abundancija, veličina klase i raspodjela biomase prirodnih populacija u odnosu na hidrološke i sedimentne karakteristike. Unatoč tome što je laguna bila pogođena eutrofikacijom, kemijskim i toplinskim zagađenjima, oko trideset profesionalnih ribara sakupljalo je školjke do 2003. godine. Dostupne zalihe stoka komercijalnih vrsta procijenjene su na 36,8 10, 3kg u srpnju 2002. godine, zatim na 29.3 10 3kg u travnju 2003. godine i na 10,3 10 3 kg u listopadu 2003. godine. Procjene zaliha i smrtnosti bile su u skladu s podacima ribara. Pad raspoloživih zaliha mogao bi biti posljedica prekomjernog izlova i izvanrednog ljetnoga toplinskog vala koji se dogodio 2003. godine, što je utjecalo na smanjenje novačenja ličinki i povećanje smrtnosti. Sveukupno gledano novačenje juvenilnih primjeraka nije bilo dovoljno za godišnje obnavljanje prirodnih zaliha. Iako je na nacionalnoj i regionalnoj razini velika važnost tržišta školjki, lokalna berba divljih populacija jest marginalna i neadekvatna za podupiranje profitabilne komercijalne aktivnosti, zbog varijabilnosti i nepredvidljivosti godišnjeg prinosa i nedostatka održivog upravljanja temeljenog na pristupu proizvodnog lanca

Steering the magnetic properties of Ni/NiO/CoO core-shell nanoparticle films: The role of core-shell interface versus interparticle interactions

Supported core-shell Ni/NiO/CoO nanoparticle (NP) films were obtained by deposition of preformed and mass-selected Ni NPs on a buffer layer of CoO, followed by a top CoO layer. The resulting NPs have core/shell morphology, with a McKay icosahedral Ni core and a partially crystalline CoO shell. X-ray photoelectron spectroscopy evidenced the presence of a thin NiO layer, which was shown to be between the Ni core and the CoO shell by elemental TEM mapping. CoO and NiO shells with different thickness values were obtained, allowing us to investigate the evolution of the magnetic properties of the NP assemblies as a function of the oxide shell thickness. Both exchange-coupling and magnetostatic interactions significantly contribute to the magnetic behavior of Ni/NiO/CoO NP films. After the Ni/NiO/CoO NPs are cooled in a weak magnetic field, they have blocking temperature higher than room temperature because of strong magnetostatic interactions, which support the formation of a spin-glass-like state below similar to 250 K. Exchange coupling dominates the magnetic behavior after the NPs are cooled in a strong magnetic field. The exchange bias (EB) is in the 0.17-2.35 kOe range and strongly depends on the CoO thickness (0.4-2.7 nm), showing the onset of the EB at the few-nanometer scale. The switching field distribution showed that the EB opposes the magnetization reversal from the direction along the cooling field but it does not significantly ease the opposite process. The EB depends on t(CoO) only for t(NiO) <= 0.5 nm, but when NiO is 0.7 nm thick it strongly interacts with CoO and a large increase of the EB and coercivity is observed

Evidence of SARS-CoV-2 bacteriophage potential in human gut microbiota

Background: In previous studies we have shown that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replicates in vitro in bacterial growth medium, that the viral replication follows bacterial growth, and it is influenced by the administration of specific antibiotics. These observations are compatible with a 'bacteriophage-like' behaviour of SARS-CoV-2. Methods: We have further elaborated on these unusual findings and here we present the results of three different supplementary experiments: (1) an electron-microscope analysis of samples of bacteria obtained from a faecal sample of a subject positive to SARS-CoV-2; (2) mass spectrometric analysis of these cultures to assess the eventual de novo synthesis of SARS-CoV-2 spike protein; (3) sequencing of SARS-CoV-2 collected from plaques obtained from two different gut microbial bacteria inoculated with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Results: Immuno-labelling with Anti-SARS-CoV-2 nucleocapsid protein antibody confirmed presence of SARS-CoV-2 both outside and inside bacteria. De novo synthesis of SARS-CoV-2 spike protein was observed, as evidence that SARS-CoV-2 RNA is translated in the bacterial cultures. In addition, phage-like plaques were spotted on faecal bacteria cultures after inoculation with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Bioinformatic analyses on the reads obtained by sequencing RNA extracted from the plaques revealed nucleic acid polymorphisms, suggesting different replication environment in the two bacterial cultures. Conclusions: Based on these results we conclude that, in addition to its well-documented interactions with eukaryotic cells, SARS-CoV-2 may act as a bacteriophage when interacting with at least two bacterial species known to be present in the human microbiota. If the hypothesis proposed, i.e., that under certain conditions SARS-CoV-2 may multiply at the expense of human gut bacteria, is further substantiated, it would drastically change the model of acting and infecting of SARS-CoV-2, and most likely that of other human pathogenic viruses

Tunability of exchange bias in Ni@NiO core-shell nanoparticles obtained by sequential layer deposition

Films of magnetic Ni@NiO core-shell nanoparticles (NPs, core diameter d\ua0 45\ua012 nm, nominal shell thickness variable between 0 and 6.5 nm) obtained with sequential layer deposition were investigated, to gain insight into the relationships between shell thickness/morphology, core-shell interface, and magnetic properties. Different values of NiO shell thickness ts could be obtained while keeping the Ni core size fixed, at variance with conventional oxidation procedures where the oxide shell is grown at the expense of the core. Chemical composition, morphology of the as-produced samples and structural features of the Ni/NiO interface were investigated with x-ray photoelectron spectroscopy and microscopy (scanning electron microscopy, transmission electron microscopy) techniques, and related with results from magnetic measurements obtained with a superconducting quantum interference device. The effect of the shell thickness on the magnetic properties could be studied. The exchange bias (EB) field Hbias is small and almost constant for ts up to 1.6 nm; then it rapidly grows, with no sign of saturation. This behavior is clearly related to the morphology of the top NiO layer, and is mostly due to the thickness dependence of the NiO anisotropy constant. The ability to tune the EB effect by varying the thickness of the last NiO layer represents a step towards the rational design and synthesis of core-shell NPs with desired magnetic properties