Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off.

Organic radicals have been of interest due to their potential to replace nonradical-based organic emitters, especially for deep-red/near-infrared (NIR) electroluminescence (EL), based on the spin-allowed doublet fluorescence. However, the performance of the radical-based EL devices is limited by low carrier mobility which causes a large efficiency roll-off at high current densities. Here, highly efficient and bright doublet EL devices are reported by combining a thermally activated delayed fluorescence (TADF) host that supports both electron and hole transport and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. Steady-state and transient photophysical studies reveal the optical signatures of doublet luminescence mechanisms arising from both host and guest photoexcitation. The host system presented here allows balanced hole and electron currents, and a high maximum external quantum efficiency (EQE) of 17.4% at 707 nm peak emission with substantially improved efficiency roll-off is reported: over 70% of the maximum EQE (12.2%) is recorded at 10 mA cm-2 , and even at 100 mA cm-2 , nearly 50% of the maximum EQE (8.4%) is maintained. This is an important step in the practical application of organic radicals to NIR light-emitting devices.

Earliest curry in Southeast Asia and the global spice trade 2000 years ago.

The global spice trade has played an essential role in world history. However, because of poor preservation conditions, archaeobotanical remains of spices have been limited in archaeological contexts until now. This study reports evidence for spice processing from the archaeological site of Oc Eo in southern Vietnam, an entrepôt of the state of Funan that was occupied during the early centuries CE. Analysis of plant microremains recovered from the surfaces of Oc Eo grinding stone tools thought to be of South Asian origin has identified culinary spices that include turmeric, ginger, fingerroot, sand ginger, galangal, clove, nutmeg, and cinnamon. These spices are indispensable ingredients used in the making of curry in South Asia today. We suggest that South Asian migrants or visitors introduced this culinary tradition into Southeast Asia during the period of early trade contact via the Indian Ocean, commencing about 2000 years ago.

Rice and millet cultivated in Ha Long Bay of Northern Vietnam 4000 years ago.

Research has generally outlined that the Neolithic East Asian farmers expanded into Southeast Asia, leading to substantial social and cultural transformations. However, the associated archaeobotanical evidence until now has been insufficient to clarify the exact timing, dispersal route, and farming package of the emergence of agriculture in Mainland Southeast Asia. To clarify these issues, the micro-plant remains of phytolith and starch from three Neolithic sites in Ha Long Bay were extracted and analyzed. This study validates the earliest evidence of co-cropping in northern Vietnam, involving the cultivation of rice together with foxtail millet at 4000 years BP or slightly earlier. Moreover, the results indicate that at least two patterns of subsistence strategy were practiced simultaneously during the initial farming phase in the region. The Trang Kenh people, a regional variant of the Phung Nguyen cultural group often have been seen as the first farmers in northern Vietnam, and they mainly practiced a cereal-based subsistence strategy with more vital cultural characteristics of southern China origin. Meanwhile, the Ha Long people, mainly composed of indigenous hunter-gatherer descendants, continued to utilize a wide range of their preferred plant resources such as taros, yams, and acorns, while they absorbed and incorporated new elements such as millet and rice into their food system. This study provides solid information to understand the diverse economic systems among different cultural groups in Vietnam.

Early Austronesians Cultivated Rice and Millet Together: Tracing Taiwan's First Neolithic Crops.

This study presents the first directly dated physical evidence of crop remains from the Early Neolithic archaeological layers in Taiwan. Systematic sampling and analysis of macro-plant remains suggested that Neolithic farmers at the Zhiwuyuan (Botanical Garden) site in Taipei, northern Taiwan, had cultivated rice and foxtail millet together at least 4,500 years ago. A more comprehensive review of all related radiocarbon dates suggests that agriculture emerged in Taiwan around 4,800-4,600 cal. BP, instead of the previous claim of 5,000 cal. BP. According to the rice grain metrics from three study sites of Zhiwuyuan, Dalongdong, and Anhe, the rice cultivated in northern and western-central Taiwan was mainly a short-grained type of the japonica subspecies, similar to the discoveries from the southeast coast of mainland China and the middle Yangtze valley. These new findings support the hypothesis that the southeast coast of mainland China was the origin of proto-Austronesian people who brought their crops and other cultural traditions across the Taiwan Strait 4,800 years ago and eventually farther into Island Southeast Asia.

Female craniometrics support the 'two-layer model' of human dispersal in Eastern Eurasia.

This study reports a cranio-morphometric analysis of female human remains from seven archaeological sites in China, Vietnam and Taiwan that date between 16,000 and 5300 BP. The aim of the analysis is to test the "two-layer" model of human dispersal in eastern Eurasia, using previously unanalysed female remains to balance the large sample of previously-analysed males. The resulting craniometric data indicate that the examined specimens all belong to the "first layer" of dispersal, and share a common ancestor with recent Australian and Papuan populations, and the ancient Jomon people of Japan. The analysed specimens pre-date the expansion of agricultural populations of East/Northeast Asian origin-that is, the "second layer" of human dispersal proposed by the model. As a result of this study, the two-layer model, which has hitherto rested on evidence only from male skeletons, is now strongly supported by female-derived data. Further comparisons reveal that the people of the first layer were closer in terms of their facial morphology to modern Africans and Sri Lankan Veddah than to modern Asians and Europeans, suggesting that the Late Pleistocene through Middle Holocene hunter-gatherers examined in this study were direct descendants of the anatomically modern humans who first migrated out of Africa through southern Eurasia.

Ancient DNA from Guam and the peopling of the Pacific.

Humans reached the Mariana Islands in the western Pacific by ∼3,500 y ago, contemporaneous with or even earlier than the initial peopling of Polynesia. They crossed more than 2,000 km of open ocean to get there, whereas voyages of similar length did not occur anywhere else until more than 2,000 y later. Yet, the settlement of Polynesia has received far more attention than the settlement of the Marianas. There is uncertainty over both the origin of the first colonizers of the Marianas (with different lines of evidence suggesting variously the Philippines, Indonesia, New Guinea, or the Bismarck Archipelago) as well as what, if any, relationship they might have had with the first colonizers of Polynesia. To address these questions, we obtained ancient DNA data from two skeletons from the Ritidian Beach Cave Site in northern Guam, dating to ∼2,200 y ago. Analyses of complete mitochondrial DNA genome sequences and genome-wide SNP data strongly support ancestry from the Philippines, in agreement with some interpretations of the linguistic and archaeological evidence, but in contradiction to results based on computer simulations of sea voyaging. We also find a close link between the ancient Guam skeletons and early Lapita individuals from Vanuatu and Tonga, suggesting that the Marianas and Polynesia were colonized from the same source population, and raising the possibility that the Marianas played a role in the eventual settlement of Polynesia.

Validating earliest rice farming in the Indonesian Archipelago.

Preserved ancient botanical evidence in the form of rice phytoliths has confirmed that people farmed domesticated rice (Oryza sativa) in the interior of Sulawesi Island, Indonesia, by at least 3,500 years ago. This discovery helps to resolve a mystery about one of the region's major events in natural and cultural history, by documenting when rice farming spread into Indonesia, ultimately from a source in mainland China. At the Minanga Sipakko site in Sulawesi, preserved leaf and husk phytoliths of rice show the diagnostic morphology of domesticated varieties, and the discarded husks indicate on-site processing of the crops. The phytoliths were contained within an undisturbed, subsurface archaeological layer of red-slipped pottery, a marker for an evidently sudden cultural change in the region that multiple radiocarbon results extend back to 3,500 years ago. The results from Minanga Sipakko allow factual evaluation of previously untested hypotheses about the timing, geographic pattern, and cultural context of the spread of rice farming into Indonesia, as well as the contribution of external immigrants in this process.

Author Correction: Craniometrics Reveal "Two Layers" of Prehistoric Human Dispersal in Eastern Eurasia.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Craniometrics Reveal "Two Layers" of Prehistoric Human Dispersal in Eastern Eurasia.

This cranio-morphometric study emphasizes a "two-layer model" for eastern Eurasian anatomically modern human (AMH) populations, based on large datasets of 89 population samples including findings directly from ancient archaeological contexts. Results suggest that an initial "first layer" of AMH had related closely to ancestral Andaman, Australian, Papuan, and Jomon groups who likely entered this region via the Southeast Asian landmass, prior to 65-50 kya. A later "second layer" shared strong cranial affinities with Siberians, implying a Northeast Asian source, evidenced by 9 kya in central China and then followed by expansions of descendant groups into Southeast Asia after 4 kya. These two populations shared limited initial exchange, and the second layer grew at a faster rate and in greater numbers, linked with contexts of farming that may have supported increased population densities. Clear dichotomization between the two layers implies a temporally deep divergence of distinct migration routes for AMH through both southern and northern Eurasia.

The prehistoric peopling of Southeast Asia.

The human occupation history of Southeast Asia (SEA) remains heavily debated. Current evidence suggests that SEA was occupied by Hòabìnhian hunter-gatherers until ~4000 years ago, when farming economies developed and expanded, restricting foraging groups to remote habitats. Some argue that agricultural development was indigenous; others favor the "two-layer" hypothesis that posits a southward expansion of farmers giving rise to present-day Southeast Asian genetic diversity. By sequencing 26 ancient human genomes (25 from SEA, 1 Japanese Jomon), we show that neither interpretation fits the complexity of Southeast Asian history: Both Hòabìnhian hunter-gatherers and East Asian farmers contributed to current Southeast Asian diversity, with further migrations affecting island SEA and Vietnam. Our results help resolve one of the long-standing controversies in Southeast Asian prehistory.

Cranio-morphometric and aDNA corroboration of the Austronesian dispersal model in ancient Island Southeast Asia: Support from Gua Harimau, Indonesia.

The Austronesian language is spread from Madagascar in the west, Island Southeast Asia (ISEA) in the east (e.g. the Philippines and Indonesian archipelagoes) and throughout the Pacific, as far east as Easter Island. While it seems clear that the remote ancestors of Austronesian speakers originated in Southern China, and migrated to Taiwan with the development of rice farming by c. 5500 BP and onto the northern Philippines by c. 4000 BP (the Austronesian Dispersal Hypothesis or ADH), we know very little about the origins and emergence of Austronesian speakers in the Indonesian Archipelago. Using a combination of cranial morphometric and ancient mtDNA analyses on a new dataset from Gua Hairmau, that spans the pre-Neolithic through to Metal Period (5712-5591cal BP to 1864-1719 cal BP), we rigorously test the validity of the ADH in ISEA. A morphometric analysis of 23 adult male crania, using 16 of Martin's standard measurements, was carried out with results compared to an East and Southeast Asian dataset of 30 sample populations spanning the Late Pleistocene through to Metal Period, in addition to 39 modern samples from East and Southeast Asia, near Oceania and Australia. Further, 20 samples were analyzed for ancient mtDNA and assigned to identified haplogroups. We demonstrate that the archaeological human remains from Gua Harimau cave, Sumatra, Indonesia provide clear evidence for at least two (cranio-morphometrically defined) and perhaps even three (in the context of the ancient mtDNA results) distinct populations from two separate time periods. The results of these analyses provide substantive support for the ADH model in explaining the origins and population history of ISEA peoples.

New radiocarbon and archaeobotanical evidence reveal the timing and route of southward dispersal of rice farming in south China.

The origins and spreads of rice agriculture have been enduring topics, yet the timing and southward dispersal from the Yangtze River Basin have been difficult to trace, due to the scarcity of archaeobotanical data, especially systematic macro-plant remains examination, combined with the poor preservation in the humid climate and acidic soils of China's southern provinces. Here, we report new radiocarbon dating and preserved rice phytolith evidence, derived from three Late Neolithic archaeological sites in south China, dated about 5,000-4,100 cal a BP. Our results demonstrate that rice farming had spread southward through the mountainous regions of Wuyi and Nanling, then entered the areas of Western Fujian and North Guangdong by 5,000 cal a BP, followed by continued expansion into coastal areas of East China Sea and South China Sea, also crossing the Taiwan Strait, around 4,500-4,000 cal a BP. The North River, East River, Min River, and possibly other river systems likely were influential as pathways or conduits.

The role of aldehyde dehydrogenase and hsp70 in suppression of white spot syndrome virus replication at high temperature.

High temperature (32 to 33°C) has been shown to reduce mortality in white spot syndrome virus (WSSV)-infected shrimps, but the mechanism still remains unclear. Here we show that in WSSV-infected shrimps cultured at 32°C, transcriptional levels of representative immediate-early, early, and late genes were initially higher than those at 25°C. However, neither the IE1 nor VP28 protein was detected at 32°C, suggesting that high temperature might inhibit WSSV protein synthesis. Two-dimensional gel electrophoresis analysis revealed two proteins, NAD-dependent aldehyde dehydrogenase (ALDH) and the proteasome alpha 4 subunit (proteasome α4), that were markedly upregulated in WSSV-infected shrimps at 32°C. Reverse transcription-PCR (RT-PCR) analysis of members of the heat shock protein family also showed that hsp70 was upregulated at 32°C. When aldh, proteasome α4, and hsp70 were knocked down by double-stranded RNA interference and shrimps were challenged with WSSV, the aldh and hsp70 knockdown shrimps became severely infected at 32°C, while the proteasome α4 knockdown shrimps remained uninfected. Our results therefore suggest that ALDH and Hsp70 both play an important role in the inhibition of WSSV replication at high temperature.

Ancient jades map 3,000 years of prehistoric exchange in Southeast Asia.

We have used electron probe microanalysis to examine Southeast Asian nephrite (jade) artifacts, many archeologically excavated, dating from 3000 B.C. through the first millennium A.D. The research has revealed the existence of one of the most extensive sea-based trade networks of a single geological material in the prehistoric world. Green nephrite from a source in eastern Taiwan was used to make two very specific forms of ear pendant that were distributed, between 500 B.C. and 500 A.D., through the Philippines, East Malaysia, southern Vietnam, and peninsular Thailand, forming a 3,000-km-diameter halo around the southern and eastern coastlines of the South China Sea. Other Taiwan nephrite artifacts, especially beads and bracelets, were distributed earlier during Neolithic times throughout Taiwan and from Taiwan into the Philippines.