Diffusion induced decoherence of stored optical vortices

We study the coherence properties of optical vortices stored in atomic ensembles. In the presence of thermal diffusion, the topological nature of stored optical vortices is found not to guarantee slow decoherence. Instead the stored vortex state has decoherence surprisingly larger than the stored Gaussian mode. Generally, the less phase gradient, the more robust for stored coherence against diffusion. Furthermore, calculation of coherence factor shows that the center of stored vortex becomes completely incoherent once diffusion begins and, when reading laser is applied, the optical intensity at the center of the vortex becomes nonzero. Its implication for quantum information is discussed. Comparison of classical diffusion and quantum diffusion is also presented.Comment: 5 pages, 2 figure

Status of transboundary diseases of penaeid shrimps in Singapore

Singapore has a small shrimp farming industry with approximately 54 metric tons (MT) of shrimps produced in one year from both land and coastal farms. There is also one shrimp farm producing broodstock for export. Singapore has the capability to diagnose acute hepatopancreatic necrosis disease (AHPND) through histopathology and the isolation of its causal agent which is Vibrio parahaemolyticus. The polymerase chain reaction (PCR) method for AHPND detection in shrimp is currently being undertaken to further strengthen its laboratory and diagnostic capacity. Notably, Singapore is still AHPND-free. On the contrary, white spot disease caused by white spot syndrome virus (WSSV) is a disease of concern as it affects the trade for ornamental crustaceans. Singapore has an active surveillance program for WSSV and other transboundary pathogens of penaeid shrimps. Positive detections would be followed by movement controls and stamping out protocols

Determining appropriate government guarantees for concession contract: lessons learned from 10 PPP projects in China

Governments worldwide are keen to encourage PPP schemes, however PPP is not a foolproof business. Many local governments and private investors have suffered severe or trying experiences. In this research, 10 case studies were conducted to identify the obstacles and difficulties for successful implementation of PPP projects from the perspective of government guarantees. These PPP projects include two water supply plants, two sewage treatment plants, two power supply plants, two highway projects, and two bridge projects. The findings obtained indicate that the local governments are familiar with “the type of guarantees” to provide to the private investor but they are unsure of the “amount” that should be given. Many PPP projects have therefore been heavily criticized for over benefiting the private investors as the government provides them with too many guarantees. The inappropriate guarantees offered by the government are regarded as one of the root causes of PPP projects’ failure. The lessons learned are valuable for determining appropriate government guarantees for future PPP projects and broadening the opportunities for infrastructure development with PPP procurement model

Rydberg atom mediated polar molecule interactions: a tool for molecular-state conditional quantum gates and individual addressability

We study the possibility to use interaction between a polar molecule in the ground electronic and vibrational state and a Rydberg atom to construct two-qubit gates between molecular qubits and to coherently control molecular states. A polar molecule within the electron orbit in a Rydberg atom can either shift the Rydberg state, or form Rydberg molecule. Both the atomic shift and the Rydberg molecule states depend on the initial internal state of the polar molecule, resulting in molecular state dependent van der Waals or dipole-dipole interaction between Rydberg atoms. Rydberg atoms mediated interaction between polar molecules can be enhanced up to $10^{3}$ times. We describe how the coupling between a polar molecule and a Rydberg atom can be applied to coherent control of molecular states, specifically, to individual addressing of molecules in an optical lattice and non-destructive readout of molecular qubits

Changes in global climate heterogeneity under the 21st century global warming

Publisher Copyright: © 2021 The Author(s)Variations in climate types are commonly used to describe changes in natural vegetation cover in response to global climate change. However, few attempts have been made to quantify the heterogeneous dynamics of climate types. In this study, based on the Coupled Model Intercomparison Project phase 5 (CMIP5) historical and representative concentration pathway (RCP) runs from 18 global climate models, we used Shannon's Diversity Index (SHDI) and Simpson's Diversity Index (SIDI) to characterise of global climate heterogeneity from a morphological perspective. Our results show that global climate heterogeneity calculated by the SHDI/SIDI indices decreased from 1901 to 2095 at a significance level of 0.01. As radiative forcing intensified from RCP 2.6 to 8.5, the SHDI/SIDI decreased significantly. Furthermore, we observed that the spatial distribution of global climate heterogeneity was significantly reduced, with a pronounced latitudinal trend. Sensitivity analysis indicated that the temperature increase played a more significant role in reducing global climate heterogeneity than precipitation under the three warming scenarios, which is possibly attributed to anthropogenic forcing. Our findings suggest that the dynamics of global climate heterogeneity can be an effective means of quantifying global biodiversity loss.Peer reviewe

Observed Changes of Koppen Climate Zones Based on High-Resolution Data Sets in the Qinghai-Tibet Plateau

Emerging and disappearing climate zones are frequently used to diagnose and project climate change. However, little attempt has been made to quantify shifts of climate zones in Qinghai-Tibet Plateau (QTP) based on the high-resolution data sets. Our results show that highland climate was decreased substantially during 1961–2011 and were mainly replaced by boreal climate. We also found that the mean elevation of boreal and highland climate continues to rise, with obvious longitudinal geographical characteristics over the study period. Furthermore, we found that the climate spaces (a climate space defined as the volume of 10°C × 500 mm here) of both boreal and highland climate types tend to be warm and humid ones, which may provide more suitable climate conditions for species to maintain and promote diversity. Characterization of changes in QTP climate types deepens our understanding of regional climate and its biological impacts.Emerging and disappearing climate zones are frequently used to diagnose and project climate change. However, little attempt has been made to quantify shifts of climate zones in Qinghai-Tibet Plateau (QTP) based on the high-resolution data sets. Our results show that highland climate was decreased substantially during 1961-2011 and were mainly replaced by boreal climate. We also found that the mean elevation of boreal and highland climate continues to rise, with obvious longitudinal geographical characteristics over the study period. Furthermore, we found that the climate spaces (a climate space defined as the volume of 10 degrees C x 500 mm here) of both boreal and highland climate types tend to be warm and humid ones, which may provide more suitable climate conditions for species to maintain and promote diversity. Characterization of changes in QTP climate types deepens our understanding of regional climate and its biological impacts. Plain Language Summary Climate classification is the key to simplifying complex climate and helps to deepen the understanding of regional climate change. Based on the high-resolution data set (LZ0025), the sharp climatic gradient features and their potential biological impact on Qinghai-Tibet Plateau (QTP) was quantified. With the temperature increase, the spatial distribution of highland tundra climate was gradually replaced by boreal climate. More importantly, the contraction of highland climate and the expansion of boreal climate has obvious elevation characteristics. In addition, climate spaces of highland and boreal climate types tend to warm and humid ones, which may provide more climatic niches for different species and contribute to regional biodiversity.Peer reviewe

From a Spatial Structure Perspective : Spatial-Temporal Variation of Climate Redistribution of China Based on the Köppen–Geiger Classification

https://doi.org/10.1029/2022GL099319Shifting climate zones are widely used to diagnose and predict regional climate change. However, few attempts have been made to measure the spatial redistribution of these climate zones from a spatial structure perspective. We investigated changes in spatial structure of Köppen climate landscape in China between 1963 and 2098 with a landscape aggregation index. Our results reveal an apparent signal from fragmentation to aggregation, accompanied by the intensification of areal dispersion between cold and warm climate types. Our attribution analysis indicates that anthropogenic forcings have a larger influence on changes of spatial structure than natural variation. We also found that topographical heterogeneity is likely to contribute to the regional spatial fragmentation, especially in the Qinghai-Tibet Plateau. However, we also found that the spatial fragmentation will be weakened around the mid-2040s. We argue that biodiversity is likely to be mediated by spatial structure of future climate landscapes in China.Peer reviewe

Vegetation response to climate zone dynamics and its impacts on surface soil water content and albedo in China

Extensive research has focused on the response of vegetation to climate change, including potential mechanisms and resulting impacts. Although many studies have explored the relationship between vegetation and climate change in China, research on spatiotemporal distribution changes of climate regimes using natural vegetation as an indicator is still lacking. Further, limited information is available on the response of vegetation to shifts in China's regional climatic zones. In this study, we applied Mann-Kendall, and correlation analysis to examine the variabilities in temperature, precipitation, surface soil water, normalised difference vegetation index (NDVI), and albedo in China from 1982 to 2012. Our results indicate significant shifts in the distribution of Koppen-Geiger climate classes in China from 12.08% to 18.98% between 1983 and 2012 at a significance level of 0.05 (MK). The percentage areas in the arid and continental zones expanded at a rate of 0.004%/y and 0.12%/y, respectively, while the percentage area in the temperate and alpine zones decreased by -0.05%/y and - 0.07%/y. Sensitivity fitting results between simulated and observed changes identified temperature to be a dominant control on the dynamics of temperate (r(2)= 0.98) and alpine (r(2)= 0.968) zones, while precipitation was the dominant control on the changes of arid (r(2) = 0.856) and continental (r(2) = 0.815) zones. The response of the NDVI to albedo infers a more pronounced radiative response in temperate (r = -0.82, pPeer reviewe

Spatial Aggregation of Global Dry and Wet Patterns Based on the Standard Precipitation Index

Quantifying the spatial integrity and patterns of dry/wet events over land is essential to understand how the local hydrological regime responds to environmental changes. Spatial aggregation changes in dry and wet areas over land have not been studied extensively. Based on a patch-mosaic landscape model, we analyzed spatial aggregation changes at two levels corresponding to landscape design during 1949 and 2018. At the landscape level, the global aggregation degree increased initially and then weakened around 2006. However, the spatial aggregation process between dry and wet patterns was inconsistent. For the dry pattern, spatial aggregation was mainly caused by area decline induced decreases in the patch number. For the wet pattern, spatial aggregation was caused by area enlargement induced decreases in the patch number. At the class level, with increases in the dry/wet magnitude, the correlation between the affected area and aggregation strengthened. Our results provide new insights to understand the spatial processes and future trends of dry/wet patterns over land. We argue that future vulnerability of agriculture and ecosystems to drought is likely to be further mediated by the changes in drought patterns' spatial structure.Peer reviewe

Electromagnetically Induced Transparency with Noisy Lasers

We demonstrate and characterize two coherent phenomena that can mitigate the effects of laser phase noise for Electromagnetically Induced Transparency (EIT): a laser-power-broadening-resistant resonance in the transmitted intensity cross-correlation between EIT optical fields; and a resonant suppression of the conversion of laser phase noise to intensity noise when one-photon noise dominates over two-photon-detuning noise. Our experimental observations are in good agreement with both an intuitive physical picture and numerical calculations. The results have wide-ranging applications to spectroscopy, atomic clocks and magnetometers.Physic