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Mechanical frequency combs are poised to bring the applications and utility of optical frequency combs into the mechanical domain. So far, their main challenge has been strict requirements on drive frequencies and power, which complicate operation. We demonstrate a straightforward mechanism to create a frequency comb consisting of mechanical overtones (integer multiples) of a single eigenfrequency, by monolithically integrating a suspended dielectric membrane with a counter-propagating optical trap. The periodic optical field modulates the dielectrophoretic force on the membrane at the overtones of a membrane’s motion. These overtones share a fixed frequency and phase relation, and constitute a mechanical frequency comb. The periodic optical field also creates an optothermal parametric drive that requires no additional power or external frequency reference. This combination of effects results in an easy-to-use mechanical frequency comb platform that requires no precise alignment, no additional feedback or control electronics, and only uses a single, mW continuous wave laser beam. This highlights the overtone frequency comb as the straightforward future for applications in sensing, metrology and quantum acoustics. The authors combined optical traps and frequency combs to create new acoustic technology – a mechanical frequency comb. The generation of this comb does not require any precision control, making it uniquely positioned for sensing, metrology, and quantum technology.

An analysis of above-ground biomass recovery during secondary succession in forest sites and plots, covering the major environmental gradients in the Neotropics. Recovery potential of disturbed tropical forests More than half the world's tropical forests are the product of secondary growth, following anthropogenic disturbance. It is therefore important to know how quickly these secondary forests recover sufficiently to provide ecosystem services equivalent to those of old-growth forest. These authors focus on carbon sequestration in Neotropical forests, and find that carbon uptake is much higher than in old-growth forest, allowing recovery to 90% of the carbon stocks in an average of 66 years, but there is also wide variation in recovery potential. This knowledge could help assess the implications of forest loss — and potential for recovery — in different areas. Land-use change occurs nowhere more rapidly than in the tropics, where the imbalance between deforestation and forest regrowth has large consequences for the global carbon cycle 1 . However, considerable uncertainty remains about the rate of biomass recovery in secondary forests, and how these rates are influenced by climate, landscape, and prior land use 2 , 3 , 4 . Here we analyse aboveground biomass recovery during secondary succession in 45 forest sites and about 1,500 forest plots covering the major environmental gradients in the Neotropics. The studied secondary forests are highly productive and resilient. Aboveground biomass recovery after 20 years was on average 122 megagrams per hectare (Mg ha −1 ), corresponding to a net carbon uptake of 3.05 Mg C ha −1  yr −1 , 11 times the uptake rate of old-growth forests. Aboveground biomass stocks took a median time of 66 years to recover to 90% of old-growth values. Aboveground biomass recovery after 20 years varied 11.3-fold (from 20 to 225 Mg ha −1 ) across sites, and this recovery increased with water availability (higher local rainfall and lower climatic water deficit). We present a biomass recovery map of Latin America, which illustrates geographical and climatic variation in carbon sequestration potential during forest regrowth. The map will support policies to minimize forest loss in areas where biomass resilience is naturally low (such as seasonally dry forest regions) and promote forest regeneration and restoration in humid tropical lowland areas with high biomass resilience.

Forest conversion to agriculture and grassland has been widespread in south-eastern Mexico. The productivity, functioning and carbon dynamics of secondary forests growing after abandonment of agricultural fields are expected to differ from those of primary forests. This study analysed whether forest age and seasonal variations affect the amount and temporal distribution of litterfall and associated nutrient transfer. Litterfall was measured across a chronosequence of semi-evergreen tropical forest in Calakmul, Yucatan peninsula, Mexico, and an index was created to evaluate the effect of land use intensity on litterfall collected in 16 stands from October 2012 to September 2014. Total litterfall ranged from 5.2 ± 0.6 to 7.1 ± 0.3 Mg ha⁻¹ year⁻¹ and peaked in secondary forest aged 10–20 years. Leaves contributed 84–91 % of total litterfall. The associated transfer of carbon ranged from 2.3 ± 0.3 to 3.2 ± 0.1 Mg ha⁻¹ year⁻¹ and of nitrogen from 62 ± 7 to 84 ± 4 kg ha⁻¹ year⁻¹. Carbon and nutrient accumulation in the organic horizon (Oa) increased significantly with forest age. However, carbon in mineral soil (down to 0.30 m depth) did not increase over time. Peaks in monthly litterfall coincided with the dry season, with higher peaks in a year with lower rainfall in the dry season. Peaks were also higher in secondary forests than in primary forests, due to changes in species composition. Higher land use intensity reduced carbon and nutrient transfer through litter in regenerating secondary forests. Longer-term research is required to analyse the climate sensitivity of litter dynamics in these tropical forest frontiers.

This paper is concerned with a novel statistical-genetic approach for the construction of linkage maps in populations obtained from reciprocal translocation heterozygotes of barley (Hordeum vulgare L.). Using standard linkage analysis, translocations usually lead to ‘pseudo-linkage': the mixing up of markers from the chromosomes involved in the translocation into a single linkage group. Close to the translocation breakpoints recombination is severely suppressed and, as a consequence, ordering markers in those regions is not feasible. The novel strategy presented in this paper is based on (1) disentangling the “pseudo-linkage” using principal coordinate analysis, (2) separating individuals into translocated types and normal types and (3) separating markers into those close to and those more distant from the translocation breakpoints. The methods make use of a consensus map of the species involved. The final product consists of integrated linkage maps of the distal parts of the chromosomes involved in the translocation.

Colorectal cancer (CRC) is a heterogeneous disease posing a challenge for accurate classification and treatment of this malignancy. There is no common genetic molecular feature that would allow for the identification of patients at risk for developing recurrences and thus selecting patients who would benefit from more stringent therapies still poses a major clinical challenge. Recently, an international multicenter consortium (CRC Subtyping Consortium) was established aiming at the classification of CRC patients in biologically homogeneous CRC subtypes. Four consensus molecular subtypes (CMSs) were identified, of which the mesenchymal CMS4 presented with worse prognosis signifying the importance of identifying these patients. Despite the large number of samples analyzed and their clear association with unifying biological programs and clinical features, single-driver mutations could not be identified and patients are heterogeneous with regard to currently used clinical markers. We therefore set out to define the regulatory mechanisms underlying the distinct gene expression profiles using a network-based approach involving multiple molecular modalities such as gene expression, methylation levels and microRNA (miR) expression. The miR-200 family presented as the most powerful determinant of CMS4-specific gene expression, tuning the majority of genes differentially expressed in the poor prognosis subtype, including genes associated with the epithelial–mesenchymal transition program. Furthermore, our data show that two epigenetic marks, namely the methylation of the two miR-200 promoter regions, can identify tumors belonging to the mesenchymal subtype and is predictive of disease-free survival in CRC patients. Importantly, epigenetic silencing of the miR-200 family is also detected in epithelial CRC cell lines that belong to the mesenchymal CMS. We thus show that determining regulatory networks is a powerful strategy to define drivers of distinct cancer subtypes, which possess the ability to identify subtype affiliation and to shed light on biological behavior.

The Starshot Breakthrough Initiative aims to send gram-scale microchip probes to Alpha Centauri within 20 years, propelled by laser-driven lightsails at a fifth of light speed. This mission demands innovative lightsail materials with meter-scale dimensions, nanoscale thickness, and billions of nanoscale holes for enhanced reflectivity and reduced mass. Unlike the microchip payload, lightsail fabrication requires breakthroughs in optics, materials science, and structural engineering. Our study uses neural topology optimization, revealing a novel pentagonal lattice-based photonic crystal (PhC) reflector. The optimized designs significantly lower the acceleration times and, thereby, launch cost. Crucially, they also enabled orders-of-magnitude fabrication cost reduction. We fabricated a 60 × 60 mm 2 , 200 nm thick reflector with over a billion nanoscale features, achieving a 9000-fold cost reduction per m 2 . This represents the highest aspect ratio nanophotonic element to date. While stringent requirements remain for lightsails, scalable, cost-effective nanophotonics present promising solutions for next-generation space exploration. Here the authors develop large-scale nanomaterials to improve the performances of laser propulsion using an easily scalable structure, thus bringing us closer to relativistic travel to our closest stars with microchip probes. These ultra-thin reflectors offer an affordable and realistic step toward lightsail space exploration.

There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at \"Los Petenes Biosphere Reserve\", in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide.

Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions. Neotropical tree community composition shows opposing successional pathways for wet and dry forests, but as vegetation cover increases over time, trends converge. Selecting species that have similar wood density to early successional communities could improve reforestation prospects.

A detailed analysis of microsporogenesis was carried out in three diploid lily cultivars (2n=2x=24) and three diploid interspecific hybrids (2n=2x=24) using DNA in situ hybridisation methods (GISH and FISH). In cvs. Gelria (Lilium longiflorum; L genome), Connecticut King and Mont Blanc (both Asiatic hybrids; Agenome) meiosis was regular and only haploid gametes were formed while the three interspecific hybrids between L. longiflorum×Asiatic hybrid (LA) showed a variable frequency of meiotic nuclear restitution and stainable 2n-pollen formation ranging from 3% to 30%. An analysis of meiotic chromosome behaviour of the LA hybrids through GISH and FISH revealed that: (1) the parental chromosomes could be clearly discriminated into univalents, half-bivalents and bivalents in the PMCs; (2) in some of the PMCs the entire complement was present either as univalents or half-bivalents which had the potential to divide equationally (following centromere division) during the first division leading to first division restitution (FDR) gametes; (3) more frequently, however, in one and the same PMC the univalents and half-bivalents divided equationally whereas the bivalents disjoined reductionally at the same time giving rise to 2n-gametes that could vary from the well-known FDR or SDR 2n-gametes. We indicate this novel type of restitution mechanism as Indeterminate Meiotic Restitution (IMR). In order to confirm the occurrence of IMR gametes, the chromosome constitutions of eight triploid BC^sub 1^ progenies derived from backcrossing the 2n-gamete producing the LAhybrids to the Asiatic hybrid parents were analysed through in situ hybridisation. The results indicated that there were seven BC^sub 1^ plants in which FDR 2n-gametes, with or without homoeologous recombinations, were functional, whereas in one case the 2n-gamete resulting from IMR was functional. In the latter, there was evidence for the occurrence of genetic recombination through homoeologous crossing-over as well as through the assortment of homoeologous chromosomes. A singular feature of the IMR 2n-gamete was that although it transmitted a euploid number of 24 chromosomes to the BC^sub 1^ progeny, the number of chromosomes transmitted from the two parental species was dissimilar: 9 L-genome chromosomes and 15 A-genome chromosomes instead of 12 of each.[PUBLICATION ABSTRACT]

Rhegmatogenous retinal detachment (RD) is a sight threatening condition. In this type of RD a break in the retina allows retrohyaloid fluid to enter the subretinal space. The prognosis concerning the patients’ visual acuity is better if the RD has not progressed to the macula. The patient is given a posturing advice of bed rest and semi-supine positioning (with the RD as low as possible) to allow the utilisation of gravity and immobilisation in preventing progression of the RD. It is, however, unknown what external loads on the eye contribute the most to the progression of a RD. The goal of this exploratory study is to elucidate the role of eye movements caused by head movements and saccades on the progression of an RD. A finite element model is produced and evaluated in this study. The model is based on geometric and material properties reported in the literature. The model shows that a mild head movement and a severe eye movement produce similar traction loads on the retina. This implies that head movements—and not eye movements—are able to cause loads that can trigger and progress an RD. These preliminary results suggest that head movements have a larger effect on the progression of an RD than saccadic eye movements. This study is the first to use numerical analysis to investigate the development and progression of RD and shows promise for future work.