Valence bond phases of herbertsmithite and related copper kagome materials

Recent evidence from magnetic torque, electron spin resonance, and second harmonic generation indicate that the prototypical quantum spin liquid candidate, herbertsmithite, has a symmetry lower than its x-ray refined trigonal space group. Here we consider known and possible distortions of this mineral class, along with related copper kagome oxides and fluorides, relate these to possible valence bond patterns, and comment on their relevance to the physics of these interesting materials

Induction of resistance and enhancing agronomic performance in grapevines under greenhouse and in open fields by applications of plasma activated water

The exposure of water to a cold atmospheric pressure plasma (CAP) enables the production of plasma activated water (PAW), having high content of reactive species, whose applications were tested on grapevine plants, both in greenhouse and in vineyard conditions. Two different CAPs were used for PAW production, evaluating their effectiveness as a possible mean to control plant diseases. Grapevines infected with yellows associated with the presence of phytoplasmas were treated evaluating qualitative and quantitative yield parameters, phytoplasma presence, and gene expression. The results show the capability of PAW to enhance plant defence mechanisms and, as demonstrated in the field trials, confirmed its ability to improve the health status of the treated plants. Quantitative (q)RT-PCR analyses allowed to determine the transcription level of genes involved in the plant defence response (phenylalanine ammonia-lyase, pal) and in the plant phytoalexin metabolism of PAW-treated materials. The number of symptomatic grapevine plants in vineyards was significantly reduced by the treatments. Transcriptional and post-transcriptional molecular analyses highlighted the PAW ability to enhance the expression of genes encoding the main enzymes involved in the phytoalexin biosynthetic pathway (flavonoids and stilbenes). The PAW ability to enhance some of the plant defence mechanisms also improving the health status of the treated plants was therefore experimentally demonstrated. After three years of trials the overall results demonstrated the possible use of PAW to reduce the disease severity, induce plant resistance both in open field and greenhouse, improving plant healthy status and grapevine yield production

Transcriptional profiling of phytoplasma infected plants treated with plasma activated water (PAW).

Background. Phytoplasmas are insect-transmitted plant pathogenic prokaryotes, associated with severe diseases in agronomic important crops. Management of these diseases has mainly focused on insect vector chemical control and on infected plant rouging. There is therefore a strong need for effective and friendly control strategies for phytoplasma-associated diseases and the possibility to use plasma activated water (PAW) as sustainable and effective method to them was therefore evaluated. PAW is produced by treating distilled water with atmospheric pressure plasmas, inducing the production of reactive oxygen and nitrogen species (RONS) and pH reduction. PAW has good potential for bacterial decontamination, degradation of organic compounds and was shown to positively affect plant growth. Methods. Sterile deionized water (SDW) was exposed to a nanosecond pulsed dielectric barrier discharge, operating in ambient air for 10 min treatment with a peak voltage of 19 kV and a pulse repetition frequency of 1 kHz, which induced production of nitrates, nitrites and peroxides, and a pH decrease. Phytoplasma infected and healthy periwinkles micropropagated shoots were exposed to PAW for about 25 minutes and gene expression studies were then performed. The theses used were: shoots treated with PAW, Fosetyl aluminum (as positive control) and SDW (as negative control), with an exposition of about 25 minutes. Nine shoots for each thesis were then collected at 6 different times after treatment and stored at -80\ub0C. Quantitative RT-PCR analyses were carried out to determine the expression level of genes involved in the plant defense response. Parallel experiments were carried out treating grapevine plants in vineyards previously tested for the phytoplasma presence. Treatments were performed for three years injecting into the plant vascular tissues 10-20 ml of PAW or sterile distilled water (as control) on each selected plant for a total of 60 plants (40 with phytoplasmas and 20 without phytoplasmas). Results. Overexpression of selected genes involved in the phytoalexin metabolism was detected in the periwinkles micropropagated shoots treated with PAW in comparison with the shoots treated with Fosetyl-Al and distilled water. In the field trials, in a relevant number of cases, the PAW-treated symptomatic plants showed reduction of symptoms, while the SDW-treated and untreated plants did not show symptom reduction. No phytotoxicity was observed in the PAW treated grapevine and periwinkle plants. Conclusion. The results obtained showed the capability of PAW to enhance plant defence mechanisms and, as demonstrated in the field trials, confirmed its ability to improve the health status of the treated plant

Plasma activated water as resistance inducer against bacterial leaf spot of tomato

Plant bacterial diseases are routinely managed with scheduled treatments based on heavy metal compounds or on antibiotics; to reduce the negative environmental impact due to the use of such chemical compounds, as pollution or selection of antibiotic resistant pathogens, the integrated control management is required. In the frame of a sustainable agriculture the use of bacterial antagonists, biological agents, plant defence response elicitors or resistant host plant genotypes are the most effective approaches. In this work, cold atmospheric pressure plasma (CAP) was applied to sterile distilled water, inducing the production of a hydrogen peroxide, nitrite and nitrate, and a pH reduction. In particular, an atmospheric pressure dielectric barrier discharge (DBD) has been used to produce plasma activated water (PAW), that was firstly assayed in in vitro experiments and then in planta through application at the root apparatus of tomato plants, against Xanthomonas vesicatoria (Xv), the etiological agent of bacterial leaf spot. Moreover, the transcription abundance of five genes related to the plant defense was investigated in response to PAW treatment. PAW did not show direct antimicrobial activity against Xv in in vitro experiments, but it enhanced the tomato plants defenses. It was effective in reducing the disease severity by giving relative protections of ca. 61, 51 and 38% when applied 1 h, 24 h and 6 days before the experimental inoculation, respectively. In addition, the experiments highlighted the pal gene involvement in response to the PAW treatments and against the pathogen; its transcription levels resulted significantly high from 1 to 48 h until their decrease 192 h after PAW application

Leggett Modes Accompanying Crystallographic Phase Transitions

Higgs and Goldstone modes, well known in high-energy physics, have been realized in a number of condensed matter physics contexts, including superconductivity and magnetism. The Goldstone-Higgs concept is also applicable to and gives rise to new insight on structural phase transitions. Here, we show that the Leggett mode, a collective mode observed in multiband superconductors, also has an analog in crystallographic phase transitions. Such structural Leggett modes can occur in the phase channel as in the original work of Leggett [Prog. Theor. Phys. 36, 901 (1966)PTPKAV0033-068X10.1143/PTP.36.901]. That is, they are antiphase Goldstone modes (antiphasons). In addition, a new collective mode can also occur in the amplitude channel, an out-of phase (antiphase) Higgs mode, that should be observable in multiband superconductors as well. We illustrate the existence and properties of these structural Leggett modes using the example of the pyrochlore relaxor ferroelectric Cd2Nb2O7

Atmospheric pressure non-equilibriumplasma for the production of composite materials

In the evolving field of tissue engineering, continuous advances are required to improve scaffold design and fabrication to obtain biomimetic supports for cell adhesion, proliferation, penetration and differentiation. Both electrospun fibrous scaffolds and hydrogels are used in this field since they well reproduce the structure of the extracellular matrix (ECM) of many biological tissues. Limitations of these two types of materials can be overcome through their combination, by developing composite structures combining enhanced mechanical properties (provided by the fibrous components) and improved cell penetration (provided by the gel phase) in a superior ability to mimic natural ECM that is constituted by both a fibrous protein network and a hydrogel matrix. Here we develop new composite materials made of electrospun PLLA scaffolds and poly(amidoamine) hydrogels with different degrees of crosslinking. To promote compatibilization and good adhesion between the two materials, surface chemical reactions between hydrogels and PLLA mats are induced by inserting amino functional groups on electrospun PLLA mats by means of atmospheric pressure non-thermal plasma. Results will be presented concerning the exposure of PLLA substrates to the plasma region generated by a Dielectric Barrier Discharge at atmospheric pressure, driven by a HV Amplifier connected to a function generator operating with a microsecond rise time and operated in N2. Surface and solid-state thermo-mechanical characterizations of plasma treated substrates and of resulting composite materials at different crosslinking degrees are presented. Results of mechanical tests show a high adhesion between hydrogel and plasma treated PLLA electrospun mats, underlining the opportunity to use atmospheric non-thermal plasmas to fabricate a composite starting from two materials otherwise physically incompatible. Potential effects of nanofibrous-hydrogel were evaluated by investigating pluripotent stem cells response

Plasma medicine: The great prospects when physics meets medicine

The research has demonstrated the antimicrobial properties of plasma urging the incorporation of cold atmospheric plasma (CAP) decontamination in current clinical therapies with the aim to improve the benefits on the patients and on society.Postprint (published version

Cold atmospheric plasma decontamination of SARS-CoV-2 bioaerosols

Bioaerosols (aerosolized particles with biological origin) are strongly suspected to play a significant role in the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), especially in closed indoor environments. Thus, control technologies capable of effectively inactivating bioaerosols are urgently needed. In this regard, cold atmospheric pressure plasma (CAP) can represent a suitable option, thanks to its ability to produce reactive species, which can exert antimicrobial action. In this study, results; on the total inactivation of SARS-CoV-2 contained in bioaerosols treated using CAP generated in air are reported, demonstrating the possible use of CAP systems for the control of SARS-CoV-2 diffusion through bioaerosols

Structural Evolution and Atom Clustering in β-SiAlON: β-Si6−z_{6-z}Alz_zOz_zN8−z_{8-z}

SiAlON ceramics, solid solutions based on the Si$_3$N$_4$ structure, are important, lightweight structural materials with intrinsically high strength, high hardness, and high thermal and chemical stability. Described by the chemical formula β-Si$_{6-z}$Al$_z$O$_z$N$_{8-z}$, from a compositional viewpoint, these materials can be regarded as solid solutions between Si$_3$N$_4$ and Al$_3$O$_3$N. A key aspect of the structural evolution with increasing Al and O ($z$ in the formula) is to understand how these elements are distributed on the β-Si$_3$N$_4$ framework. The average and local structural evolution of highly phase-pure samples of β-Si$_{6-z}$Al$_z$O$_z$N$_{8-z}$ with $z$ = 0.050, 0.075, and 0.125 are studied here, using a combination of X-ray diffraction, NMR studies, and density functional theory calculations. Synchrotron X-ray diffraction establishes sample purity and indicates subtle changes in the average structure with increasing Al content in these compounds. Solid-state magic-angle-spinning $^{27}$Al NMR experiments, coupled with detailed ab initio calculations of NMR spectra of Al in different AlO$_q$N$_{4-q}$ tetrahedra (0 ≤ $q$ ≤ 4), reveal a tendency of Al and O to cluster in these materials. Independently, the calculations suggest an energetic preference for Al-O bond formation, instead of a random distribution, in the β-SiAlON system.C.C. thanks the National Science Foundation for a Graduate Research Fellowship under Grant DGE 1144085. K.J.G. thanks The Winston Churchill Foundation of the United States and the Herchel Smith Scholarship for funding. Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE), Office of Science, by Argonne National Laboratory, was supported by the U.S. DOE under Contract DE-AC02-06CH11357. DFT calculations were performed on the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council (U.K.). This work made use of MRL-shared experimental facilities, supported by the MRSEC Program of the NSF under Award DMR 1121053. The MRL is a member of the NSF-funded Materials Research Facilities Network (www.mrfn.org)

Enhanced Electrospinning of Active Organic Fibers by Plasma Treatment on Conjugated Polymer Solutions

Realizing active, light-emitting fibers made of conjugated polymers by the electrospinning method is generally challenging. Electrospinning of plasma-treated conjugated polymer solutions is here developed for the production of light-emitting microfibers and nanofibers. Active fibers from conjugated polymer solutions rapidly processed by a cold atmospheric argon plasma are electrospun in an effective way, and they show a smoother surface and bead-less morphology, as well as preserved optical properties in terms of absorption, emission, and photoluminescence quantum yield. In addition, the polarization of emitted light and more notably photon waveguiding along the length of individual fibers are remarkably enhanced by electrospinning plasma-treated solutions. These properties come from a synergetic combination of favorable intermolecular coupling in the solutions, increased order of macromolecules on the nanoscale, and resulting fiber morphology. Such findings make the coupling of the electrospinning method and cold atmospheric plasma processing on conjugated polymer solutions a highly promising and possibly general route to generate light-emitting and conductive micro- and nanostructures for organic photonics and electronics