Prospects for regenerative agriculture in Chile

A global perspective, why we need a greener agriculture? “I am a photosynthesis manager and an ecosystem service provider”. This profound statement was made by a Swedish farmer some years ago (Wratten, 2018). Few farmers describe their occupation in this way. However, there is a major body of work giving substantial evidence that current high-input farming (Figure 1) has no future without changes to its approach (Pretty et al., 2018). One reason for this view is that agriculture is one of the main causes of climate disturbance, largely driven by changes in land-use practices (Bennetzen et al., 2016). The main consequence has been biodiversity loss (Sala et al., 2000). A very worrying example of this is that human activities have made 60% of mammal, bird, fish and reptile species extinct since 1970, as consumption of food and resources by the global human population has de-stabilised the ‘web of life’ (Carrington and Watts, 2018). In more scientific language, we are losing ecosystem functions provided by nature at an alarming rate and with that, ecosystem (nature’s) services are declining rapidly. Examples are declines in pollination, predation of pests and soil services. The seriousness of these losses was recently reported by workers at the University of Sheffield, UK, who predicted that Britain has only 100 harvests remaining before that country’s soils are no longer suitable for growing crops (Dunnett, 2014)

Ecological and pest-management implications of sex differences in scarab landing patterns on grape vines

Background: Melolonthinae beetles, comprising different white grub species, are a globally-distributed pest group. Their larvae feed on roots of several crop and forestry species, and adults can cause severe defoliation. In New Zealand, the endemic scarab pest Costelytra zealandica (White) causes severe defoliation on different horticultural crops, including grape vines (Vitis vinifera). Understanding flight and landing behaviours of this pest can help inform pest management decisions. Methods: Adult beetles were counted and then removed from 96 grape vine plants from 21:30 until 23:00 h, every day from October 26 until December 2, during 2014 and 2015. Also, adults were removed from the grape vine foliage at dusk 5, 10, 15, 20 and 25 min after flight started on 2015. Statistical analyses were performed using generalised linear models with a beta-binomial distribution to analyse proportions and with a negative binomial distribution for beetle abundance. Results: By analysing C. zealandica sex ratios during its entire flight season, it is clear that the proportion of males is higher at the beginning of the season, gradually declining towards its end. When adults were successively removed from the grape vines at 5-min intervals after flight activity begun, the mean proportion of males ranged from 6-28%. The male proportion suggests males were attracted to females that had already landed on grape vines, probably through pheromone release. Discussion: The seasonal and daily changes in adult C. zealandica sex ratio throughout its flight season are presented for the first time. Although seasonal changes in sex ratio have been reported for other melolonthines, changes during their daily flight activity have not been analysed so far. Sex-ratio changes can have important consequences for the management of this pest species, and possibly for other melolonthines, as it has been previously suggested that C. zealandica females land on plants that produce a silhouette against the sky. Therefore, long-term management might evaluate the effect of different plant heights and architecture on female melolonthine landing patterns, with consequences for male distribution, and subsequently overall damage within horticultural areas

Beating dark-dark solitons in Bose-Einstein condensates

Motivated by recent experimental results, we study beating dark-dark solitons as a prototypical coherent structure that emerges in two-component Bose-Einstein condensates. We showcase their connection to dark- bright solitons via SO(2) rotation, and infer from it both their intrinsic beating frequency and their frequency of oscillation inside a parabolic trap. We identify them as exact periodic orbits in the Manakov limit of equal inter- and intra-species nonlinearity strengths with and without the trap and showcase the persistence of such states upon weak deviations from this limit. We also consider large deviations from the Manakov limit illustrating that this breathing state may be broken apart into dark-antidark soliton states. Finally, we consider the dynamics and interactions of two beating dark-dark solitons in the absence and in the presence of the trap, inferring their typically repulsive interaction.Comment: 13 pages, 14 figure

Hahb-4, a homeobox-leucine zipper gene potentially involved in abscisic acid-dependent responses to water stress in sunflower

The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers AF339748 and AF339749.Homeodomain-leucine zipper proteins constitute a family of transcription factors found only in plants. We have characterized a full-length cDNA encoding the sunflower homeobox-leucine zipper protein Hahb-4 (Helianthus annuus homeo box-4). The complete cDNA is 674 base pairs long and contains an open reading frame of 177 amino acids that belongs to the Hd-Zip I subfamily. Northern blot and RNAse A protection analysis show that the expression of Hahb-4 is rapidly, strongly and reversibly induced by water deficit in whole seedlings, roots, stems and leaves. A similar fast induction of Hahb-4 expression is observed when seedlings are subjected to a treatment with the hormone abscisic acid (ABA). Nuclei prepared from seedlings treated with ABA or subjected to water stress show a significant increase of protein(s) that specifically bind the sequence 5′-CAAT(A/T)ATTG-3′, recognized in vitro by Hahb-4, suggesting that an active protein is synthesized in response to these treatments. The promoter region of the Hahb-4 gene contains sequences that fit the consensus for a G-box present in some ABA responsive elements (ABREs). We propose that Hahb-4 may function in signalling cascade(s) that control(s) a subset of the ABAmediated responses of sunflower to water stress.This work was supported by grants from CONICET, ANPCyT, Fundación Antorchas (Argentina) and Universidad Nacional del Litoral. R.L.C. and D.H.G. are members of CONICET; G.M.G. is a fellow of the same Institution. The laboratory work of J.J. and C.A. was also supported by grants BIO99-794 (from the Spanish Comisión Interministerial de Ciencia y Tecnología) and CVI 148 (from Plan Andaluz de Investigación).Peer reviewe

Predicting a Gapless Spin-1 Neutral Collective Mode branch for Graphite

Using the standard tight binding model of 2d graphite with short range electron repulsion, we find a gapless spin-1, neutral collective mode branch {\em below the particle-hole continuum} with energy vanishing linearly with momenta at the $\Gamma$ and $K$ points in the BZ. This spin-1 mode has a wide energy dispersion, 0 to $\sim 2 eV$ and is not Landau damped. The `Dirac cone spectrum' of electrons at the chemical potential of graphite generates our collective mode; so we call this `spin-1 zero sound' of the `Dirac sea'. Epithermal neutron scattering experiments, where graphite single crystals are often used as analyzers (an opportunity for `self-analysis'!), and spin polarized electron energy loss spectroscopy (SPEELS) can be used to confirm and study our collective mode.Comment: 4 pages of LaTex file, 3 eps figure file

Applications of Direct Injection Soft Chemical Ionisation-Mass Spectrometry for the Detection of Pre-blast Smokeless Powder Organic Additives

Analysis of smokeless powders is of interest from forensics and security perspectives. This article reports the detection of smokeless powder organic additives (in their pre-detonation condition), namely the stabiliser diphenylamine and its derivatives 2-nitrodiphenylamine and 4-nitrodiphenylamine, and the additives (used both as stabilisers and plasticisers) methyl centralite and ethyl centralite, by means of swab sampling followed by thermal desorption and direct injection soft chemical ionisation-mass spectrometry. Investigations on the product ions resulting from the reactions of the reagent ions H3O+ and O2+ with additives as a function of reduced electric field are reported. The method was comprehensively evaluated in terms of linearity, sensitivity and precision. For H3O+, the limits of detection (LoD) are in the range of 41-88 pg of additive, for which the accuracy varied between 1.5 and 3.2%, precision varied between 3.7 and 7.3% and linearity showed R20.9991. For O2+, LoD are in the range of 72 to 1.4 ng, with an accuracy of between 2.8 and 4.9% and a precision between 4.5 and 8.6% and R20.9914. The validated methodology was applied to the analysis of commercial pre-blast gun powders from different manufacturers.(VLID)4826148Accepted versio

CMB polarization as a probe of the anomalous nature of the Cold Spot

One of the most interesting explanations for the non-Gaussian Cold Spot (CS) detected in the WMAP data by Vielva et al. 2004, is that it arises from the interaction of the CMB radiation with a cosmic texture (Cruz et al. 2007b). In this case, a lack of polarization is expected in the region of the spot, as compared to the typical values associated to large fluctuations of a GIRF. In addition, other physical processes related to a non-linear evolution of the gravitational field could lead to a similar scenario. However, some of these alternative scenarios (e.g., a large void in the large scale structure) have been shown to be very unlikely. In this work we characterise the polarization properties of the Cold Spot under both hypotheses: a large Gaussian spot and an anomalous feature generated, for instance, by a cosmic texture. We propose a methodology to distinguish between them, and we discuss its discrimination power as a function of the instrumental noise level. In particular, we address the cases of current experiments, like WMAP and Planck, and others in development as QUIJOTE. We find that for an ideal experiment the Gaussian hypothesis could be rejected at a significance level better than 0.8%. While WMAP is far from providing useful information in this respect, we find that Planck will be able to reach a significance of around 7%; in addition, we show that the ground-based experiment QUIJOTE could provide a significance of around 1%. If these results are combined with the significance level found for the CS in temperature, the capability of QUIJOTE and Planck to reject the alternative hypothesis becomes 0.025% and 0.124%, respectively.Comment: 7 pages, 3 figures, accepted in MNRAS. Minor changes made to match the final versio

Conical intersection and coherent vibrational dynamics in alkyl iodides captured by attosecond transient absorption spectroscopy

The photodissociation dynamics of alkyl iodides along the C–I bond are captured by attosecond extreme-ultraviolet (XUV) transient absorption spectroscopy employing resonant ∼20 fs UV pump pulses. The methodology of previous experiments on CH3I [Chang et al., J. Chem. Phys. 154, 234301 (2021)] is extended to the investigation of a C–I bond-breaking reaction in the dissociative A-band of C2H5I, i-C3H7I, and t-C4H9I. Probing iodine 4d core-to-valence transitions in the XUV enables one to map wave packet bifurcation at a conical intersection in the A-band as well as coherent vibrations in the ground state of the parent molecules. Analysis of spectroscopic bifurcation signatures yields conical intersection crossing times of 15 ± 4 fs for CH3I, 14 ± 5 fs for C2H5I, and 24 ± 4 fs for i-C3H7I and t-C4H9I, respectively. Observations of coherent vibrations, resulting from a projection of A-band structural dynamics onto the ground state by resonant impulsive stimulated Ramanscattering, indirectly reveal multimode C–I stretch and CCI bend vibrations in the A-bands of C2H5I, i-C3H7I, and t-C4H9

Uniqueness and Nondegeneracy of Ground States for (−Δ)sQ+Q−Qα+1=0(-\Delta)^s Q + Q - Q^{\alpha+1} = 0 in R\mathbb{R}

We prove uniqueness of ground state solutions $Q = Q(|x|) \geq 0$ for the nonlinear equation $(-\Delta)^s Q + Q - Q^{\alpha+1}= 0$ in $\mathbb{R}$, where $0 < s < 1$ and $0 < \alpha < \frac{4s}{1-2s}$ for $s < 1/2$ and $0 < \alpha < \infty$ for $s \geq 1/2$. Here $(-\Delta)^s$ denotes the fractional Laplacian in one dimension. In particular, we generalize (by completely different techniques) the specific uniqueness result obtained by Amick and Toland for $s=1/2$ and $\alpha=1$ in [Acta Math., \textbf{167} (1991), 107--126]. As a technical key result in this paper, we show that the associated linearized operator $L_+ = (-\Delta)^s + 1 - (\alpha+1) Q^\alpha$ is nondegenerate; i.\,e., its kernel satisfies $\mathrm{ker}\, L_+ = \mathrm{span}\, \{Q'\}$. This result about $L_+$ proves a spectral assumption, which plays a central role for the stability of solitary waves and blowup analysis for nonlinear dispersive PDEs with fractional Laplacians, such as the generalized Benjamin-Ono (BO) and Benjamin-Bona-Mahony (BBM) water wave equations.Comment: 45 page