Temperate rainforests near the South Pole during peak Cretaceous warmth.

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years1-5, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume6. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf-the southernmost Cretaceous record reported so far-and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian-Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120-1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

Surgery or Endovascular Therapy for Chronic Limb-Threatening Ischemia.

BACKGROUND: Patients with chronic limb-threatening ischemia (CLTI) require revascularization to improve limb perfusion and thereby limit the risk of amputation. It is uncertain whether an initial strategy of endovascular therapy or surgical revascularization for CLTI is superior for improving limb outcomes. METHODS: In this international, randomized trial, we enrolled 1830 patients with CLTI and infrainguinal peripheral artery disease in two parallel-cohort trials. Patients who had a single segment of great saphenous vein that could be used for surgery were assigned to cohort 1. Patients who needed an alternative bypass conduit were assigned to cohort 2. The primary outcome was a composite of a major adverse limb event - which was defined as amputation above the ankle or a major limb reintervention (a new bypass graft or graft revision, thrombectomy, or thrombolysis) - or death from any cause. RESULTS: In cohort 1, after a median follow-up of 2.7 years, a primary-outcome event occurred in 302 of 709 patients (42.6%) in the surgical group and in 408 of 711 patients (57.4%) in the endovascular group (hazard ratio, 0.68; 95% confidence interval [CI], 0.59 to 0.79; P<0.001). In cohort 2, a primary-outcome event occurred in 83 of 194 patients (42.8%) in the surgical group and in 95 of 199 patients (47.7%) in the endovascular group (hazard ratio, 0.79; 95% CI, 0.58 to 1.06; P = 0.12) after a median follow-up of 1.6 years. The incidence of adverse events was similar in the two groups in the two cohorts. CONCLUSIONS: Among patients with CLTI who had an adequate great saphenous vein for surgical revascularization (cohort 1), the incidence of a major adverse limb event or death was significantly lower in the surgical group than in the endovascular group. Among the patients who lacked an adequate saphenous vein conduit (cohort 2), the outcomes in the two groups were similar. (Funded by the National Heart, Lung, and Blood Institute; BEST-CLI ClinicalTrials.gov number, NCT02060630.).

Reducing aneurysm sac growth and secondary interventions following endovascular abdominal aortic aneurysm repair by preemptive coil embolization of the inferior mesenteric artery and lumbar arteries.

OBJECTIVE: Type II endoleak (EL-2) is the most common complication following endovascular aneurysm repair (EVAR), leading to continued sac growth and potential rupture. In this study, we examined the association between patency of the inferior mesenteric artery (IMA) and lumbar arteries (LAs) with respect to sac growth. The effect of preemptive embolization of the IMA and/or LAs on the need for secondary interventions for sac growth post-EVAR was also evaluated. METHODS: A retrospective cohort study was performed on consecutive patients who underwent EVAR for non-ruptured, infrarenal abdominal aortic aneurysms (AAAs) from January 2012 to December 2020. A select group of patients underwent preemptive embolization of the IMA and/or LA. Patients with any types I, III, or IV endoleaks were excluded. Patency of the IMA and LA on preoperative computed tomography angiogram (CTA) was evaluated on TeraRecon workstation. All secondary interventions to treat EL-2 were recorded. Sac growth was defined as centerline axial diameter increase of ≥5 mm on follow-up CTA. RESULTS: A total of 300 patients (mean age, 74 ± 8.5 years; 83.7% male) underwent EVAR. Ninety-nine patients had preemptive embolization of the IMA and/or LA. Mean follow-up of the cohort was 59.3 ± 30.5 months. Thirty-six patients (12%) demonstrated sac growth on follow-up; 12 of these (33.3%) had preemptive embolization. The median time until detection of sac growth was 28.8 months (interquartile range, 15.2-46.5 months), with a mean growth of 10.1 ± 6.4 mm. Sac growth was significantly associated with presence of EL-2: 27 of 36 (75%) with EL-2 vs 9 of 36 (25%) without EL-2 (P < .001). Patients with sac growth had a higher mean total number (2.6 ± 1.5) of patent lower LAs (L3, L4) compared with those without (2.0 ± 1.4; P = .03). Patency of L1, L2, and L3 LAs were not associated with sac growth. However, patency of at least one L4 LA was significantly associated with sac growth (14.8% vs 7.7%; P = .04). The highest incidence of sac growth (17.6%) was seen when both IMA and L4 LA were patent; significantly different from the lowest incidence (5.3%) when both were occluded preoperatively (P = .018). Preemptive coiling of the IMA and/or LA significantly reduced the need for post-EVAR secondary intervention for sac growth. Freedom from post-EVAR secondary intervention was achieved in 92 of 99 (92.9%) pre-EVAR coiled patients vs 163 of 201 (81.5%) patients who did not undergo pre-EVAR coiling (P = .009). CONCLUSIONS: Preemptive coil embolization of the IMA and LAs, especially L4 LA, reduces the need for secondary interventions for sac growth, potentially improving the long-term durability of EVAR.

From Primary to Tertiary Care: Expert Position Statements to Guide Heart Failure with Preserved Ejection Fraction Diagnosis.

Globally, heart failure with preserved ejection fraction (HFpEF) is quickly becoming the dominant form of heart failure (HF) in ageing populations. However, there are still multiple gaps and challenges in making a firm diagnosis of HFpEF in many low-to-middle income Asian countries. In response to this unmet need, the Malaysian HFpEF Working Group (MY-HPWG) gathered and reviewed evidence surrounding the use of different diagnostic modalities indicated for patients with HFpEF to identify diagnostic tools that could be conveniently accessed across different healthcare settings. As a result, five recommendation statements were proposed and an accompanying algorithm was developed, with the aim of improving the diagnostic rate of HFpEF. The MY-HPWG recommends using more easily accessible and non-invasive tools, such as natriuretic peptide (NP) biomarkers and basic echocardiogram (ECHO), to ensure timely HFpEF diagnosis in the primary and secondary care settings, and prompt referral to a tertiary care centre for more comprehensive assessments in uncertain cases.

The role of the inferior mesenteric artery in predicting secondary intervention for type II endoleak following endovascular aneurysm repair.

OBJECTIVE: Endovascular aneurysm repair (EVAR) is associated with a greater risk of graft-related complications and need for secondary interventions compared with open repair. Type II endoleak (EL-2) is the most common complication. We examined the hypothesis that a functionally occluded inferior mesenteric artery (IMA) before EVAR was associated with fewer secondary interventions for EL-2. METHODS: All nonruptured abdominal aortic aneurysms (AAA) treated by EVAR using U.S. Food and Drug Administration-approved endografts from January 2005 to December 2017 were retrospectively reviewed, including computed tomography angiograms. Preoperative patency of the IMA and any secondary interventions performed after the index EVAR procedure were recorded. A functionally occluded IMA was defined as one that was (1) chronically occluded or severely stenosed on preoperative imaging or (2) coil embolized before EVAR. Secondary interventions for persistent EL-2 were indicated when AAA sac diameter increased by more than 5 mm. RESULTS: The study cohort comprised 490 patients (84 women) with a mean age of 74.8 ± 8.2 years. The mean preoperative AAA diameter was 5.6 ± 0.9 cm. One hundred twenty-nine patients (26.3%) died during follow-up. The mean follow-up of survivors was 38 months. Types (prevalence) of endoleak were I (2.4%), II (18.9%), III (0.7%), IV (0.5%), and V (0.2%). Patients with a functionally occluded IMA underwent significantly fewer secondary interventions for EL-2 compared with patients with a patent IMA (2.6% vs 7.1%; P = .020). All secondary interventions in the functionally occluded IMA group involved the lumbar arteries (LA). When the IMA was patent, secondary interventions were equally distributed between the LA and IMA. Logistic regression confirmed that a functionally patent IMA was associated with a greater number of secondary interventions for EL-2 (odds ratio, 3.0; 95% confidence interval, 1.2-7.5; P = .025). CONCLUSIONS: Patients with a functionally occluded IMA required significantly fewer secondary interventions for EL-2 after EVAR. In addition, the type of vessels intervened on were primarily LA. Among patients with a patent IMA, preoperative coil embolization may decrease secondary interventions and improve the long-term durability of EVAR.

Role of type II endoleak in sac regression after endovascular repair of infrarenal abdominal aortic aneurysms.

OBJECTIVE: Endovascular repair (EVAR) of infrarenal aortic aneurysms (AAA) is increasingly used in patients with suitable aortic morphology conforming to device-specific instructions for use. Despite improvements in graft design, type II endoleak (EL-2) from the inferior mesenteric artery (EL-IMA) or the lumbar artery (EL-LA) remains the Achilles' heel of EVAR. The objective of this study was to evaluate the natural history of the AAA sac after EVAR. We hypothesized that persistent EL-2 would be associated with inferior AAA sac volume regression. METHODS: A retrospective analysis was performed on all nonruptured AAA treated by elective EVAR using Food and Drug Administration-approved endografts from January 2005 to December 2008 in our facility. Review of medical records and preoperative and follow-up computed tomography angiograms at 1, 6, and 12 months was performed. Patients with type I, III, and IV endoleaks were excluded, as were those lost to all follow-up. AAA size and volume were analyzed using TeraRecon software (Aquarius Intuition, Foster City, Calif). Change in AAA sac volume was compared in patients with and without EL-2, and with an occluded vs patent IMA. RESULTS: The study cohort comprised 191 patients (161 men, 30 women) with a mean age of 74 years. The mean preoperative AAA diameter was 5.5 cm (range, 4-11 cm), and mean volume was 137.45 cm(3). EL-2 was present in 24% at completion of EVAR and in 9% at a mean follow-up of 6 months (range 4-8 months). Completion angiography at 1 month showed 63% of EL-2 had resolved. Those with EL-2 present at 1 month had statistically inferior sac regression compared with those who did not (23% reduction vs 2% increase at 1 year; P = .002). Preoperatively, the IMA was occluded by coils or was chronically occluded in 82 patients vs 109 patients who had a patent IMA. At the 6-month follow-up, patients with an occluded IMA had an EL-2 rate of 2.4% vs 14.7% in those with a patent IMA (P = .005 by t-test). Sac volume regression was 21.8% in those with an occluded IMA vs 13.2% in those with a patent IMA (P = .004 by t-test). Regression in AAA sac volume was highly significant in patients with occluded IMA, at 30% vs 16% at 1 year (P = .0018 by two-sided t-test). CONCLUSIONS: The presence of persistent EL-2 after EVAR results in inferior AAA sac regression. A preoperatively patent IMA is associated with increased rates of EL-2 and inferior AAA sac regression. Consideration should be given to preoperative occlusion of a patent IMA before EVAR.

Prehospital Trauma Care in Singapore.

Prehospital emergency care in Singapore has taken shape over almost a century. What began as a hospital-based ambulance service intended to ferry medical cases was later complemented by an ambulance service under the Singapore Fire Brigade to transport trauma cases. The two ambulance services would later combine and come under the Singapore Civil Defence Force. The development of prehospital care systems in island city-state Singapore faces unique challenges as a result of its land area and population density. This article defines aspects of prehospital trauma care in Singapore. It outlines key historical milestones and current initiatives in service, training, and research. It makes propositions for the future direction of trauma care in Singapore. The progress Singapore has made given her circumstances may serve as lessons for the future development of prehospital trauma systems in similar environments. Key words: Singapore; trauma; prehospital emergency care; emergency medical services.

A real-time recording model of key indicators for energy consumption and carbon emissions of sustainable buildings.

Buildings' sustainability is one of the crucial parts for achieving urban sustainability. Applied to buildings, life-cycle assessment encompasses the analysis and assessment of the environmental effects of building materials, components and assemblies throughout the entire life of the building construction, use and demolition. Estimate of carbon emissions is essential and crucial for an accurate and reasonable life-cycle assessment. Addressing the need for more research into integrating analysis of real-time and automatic recording of key indicators for a more accurate calculation and comparison, this paper aims to design a real-time recording model of these crucial indicators concerning the calculation and estimation of energy use and carbon emissions of buildings based on a Radio Frequency Identification (RFID)-based system. The architecture of the RFID-based carbon emission recording/tracking system, which contains four functional layers including data record layer, data collection/update layer, data aggregation layer and data sharing/backup layer, is presented. Each of these layers is formed by RFID or network devices and sub-systems that operate at a specific level. In the end, a proof-of-concept system is developed to illustrate the implementation of the proposed architecture and demonstrate the feasibility of the design. This study would provide the technical solution for real-time recording system of building carbon emissions and thus is of great significance and importance to improve urban sustainability.

A large-scale transcontinental river system crossed West Antarctica during the Eocene.

Extensive ice coverage largely prevents investigations of Antarctica's unglaciated past. Knowledge about environmental and tectonic development before large-scale glaciation, however, is important for understanding the transition into the modern icehouse world. We report geochronological and sedimentological data from a drill core from the Amundsen Sea shelf, providing insights into tectonic and topographic conditions during the Eocene (~44 to 34 million years ago), shortly before major ice sheet buildup. Our findings reveal the Eocene as a transition period from >40 million years of relative tectonic quiescence toward reactivation of the West Antarctic Rift System, coinciding with incipient volcanism, rise of the Transantarctic Mountains, and renewed sedimentation under temperate climate conditions. The recovered sediments were deposited in a coastal-estuarine swamp environment at the outlet of a >1500-km-long transcontinental river system, draining from the rising Transantarctic Mountains into the Amundsen Sea. Much of West Antarctica hence lied above sea level, but low topographic relief combined with low elevation inhibited widespread ice sheet formation.

The influence of Cenozoic Eurasia-Arabia convergence on the Southeast Arabian Foreland Basin: new geochronological and geochemical constraints from syn-kinematic carbonate mineralization.

The Cenozoic succession of the Jabal Hafeet anticline yields the most complete surface expression of the deformation that affected the Southeast Arabian Foreland Basin (SEAFB). The carbonate rocks of the Eocene Rus Formation comprise the core of the Jabal Hafeet anticline and host a network of fractures and carbonate veins associated with dynamic fracture opening and sealing events. These fracture networks developed during the propagation of compressional stresses from the Makran and Zagros fold-and-thrust belts into their foreland basin system (the SEAFB) and are associated with Arabia-Eurasia convergence. Syn-kinematic calcite veins associated with the Cenozoic folding events in the SEAFB were dated by U-Pb LA-ICP-MS carbonate geochronology and characterized further by Raman fluid-inclusion geochemistry. The U-Pb data show that Cenozoic compression linked to the propagation of the Makran fold-and-thrust belt into the SEAFB took place from c. 20 Ma (early Miocene) to c. 2 Ma (mid Pleistocene). Raman fluid-inclusion data reveal the presence of complex hydrocarbons within the parent carbonate-bearing fluids, reflecting a fluid transport pathway between the upper Cenozoic rocks and deeper hydrocarbon-bearing Mesozoic sequences. Combined isotopic and geochemical datasets show that the deformational history of the SEAFB is likely related to the reactivation of inherited deep-seated structures in the upper Cenozoic stratigraphic sequence due to the far-field stress propagation from the Makran belt into the Arabian peninsula, rather than the propagation of a thin-skinned deformation architecture.

Constraining the tectonic evolution of rifted continental margins by U-Pb calcite dating.

We employ U-Pb calcite dating of structurally-controlled fracture fills within crystalline Caledonian basement in western Norway to reveal subtle large-scale tectonic events that affected this rifted continental margin. The ages (15 in total) fall into four distinct groups with ages mainly ranging from latest Cretaceous to Pleistocene. (1) The three oldest (Triassic-Jurassic) ages refine the complex faulting history of a reactivated fault strand originated from the Caledonian collapse and broadly correlate with known rifting events offshore. (2) Two ages of ca. 90-80 Ma relate to lithospheric stretching and normal fault reactivation of a major ENE-WSW trending late Caledonian shear zone. (3) We correlate five ages between ca. 70 and 60 Ma with far-field effects and dynamic uplift related to the proto-Iceland mantle plume, the effect and extent of which is highly debated. (4) The five youngest ages (< 50 Ma) from distinct NE-SW trending faults are interpreted to represent several episodes of post-breakup fracture dilation, indicating a long-lived Cenozoic deformation history. Our new U-Pb data combined with structural and isotopic data show that much larger tracts of the uplifted continental margin of western Norway have been affected by far-field tectonic stresses than previously anticipated, with deformation continuing into the late Cenozoic.

Collision with Gondwana or with Baltica? Ordovician magmatic arc volcanism in the Marmarosh Massif (Eastern Carpathians, Ukraine).

The pre-Alpine Marmarosh Massif is a tectonically complex unit of the crystalline basement within the Eastern Outer Carpathians. In the eastern (Ukrainian) segment of this massif, two units have been identified-the Bilyi Potok Nappe and the Dilove Nappe. Petrological investigations coupled with zircon U-Pb dating were performed on metavolcanic rocks (porphyroids) and their phyllite host rocks, sampled from three locations within the Dilove Nappe. The geochemical characteristics of the meta-rhyodacite porphyroids revealed a volcanic arc affinity of the protolith, with U-Pb zircon ages of 452.8 ± 1.5 Ma and 461.5 ± 1.6 Ma and zircon saturation temperatures in the range of 823-892 °C. The phyllite host rocks (meta-tuff) yield a U-Pb zircon maximum estimate for the eruption age at 584.7 ± 2.9 Ma. Peak amphibolite-facies metamorphism (M1) was estimated at the pressure of 600-900 MPa with a temperature range of 560-600 °C. Retrogression (M2), possibly related to Alpine nappe stacking and shearing, is assumed to have taken place at 200-250 MPa and 384-222 °C. The volcanic arc is interpreted as an early Caledonian arc that was subsequently accreted to the margin of Baltica during the closure of the easternmost Tornquist Ocean rather than Cenerian (early Paleozoic) orogenic events on the margin of East Gondwana. Supplementary Information: The online version contains supplementary material available at 10.1007/s00531-022-02228-8.

Endogenous ADAR-mediated RNA editing in non-human primates using stereopure chemically modified oligonucleotides.

Technologies that recruit and direct the activity of endogenous RNA-editing enzymes to specific cellular RNAs have therapeutic potential, but translating them from cell culture into animal models has been challenging. Here we describe short, chemically modified oligonucleotides called AIMers that direct efficient and specific A-to-I editing of endogenous transcripts by endogenous adenosine deaminases acting on RNA (ADAR) enzymes, including the ubiquitously and constitutively expressed ADAR1 p110 isoform. We show that fully chemically modified AIMers with chimeric backbones containing stereopure phosphorothioate and nitrogen-containing linkages based on phosphoryl guanidine enhanced potency and editing efficiency 100-fold compared with those with uniformly phosphorothioate-modified backbones in vitro. In vivo, AIMers targeted to hepatocytes with N-acetylgalactosamine achieve up to 50% editing with no bystander editing of the endogenous ACTB transcript in non-human primate liver, with editing persisting for at least one month. These results support further investigation of the therapeutic potential of stereopure AIMers.

The Effect of Abdominal Aortic Aneurysm Size on Endoleak, Secondary Intervention and Overall Survival Following Endovascular Aortic Aneurysm Repair.

OBJECTIVE: The purpose of this study was to identify the effect of abdominal aortic aneurysm (AAA) size on endoleak development and secondary intervention after endovascular repair (EVAR), as well as to examine the effect on overall survival and cause of mortality. METHODS: Retrospective analysis was performed on all non-ruptured AAA treated by elective EVAR using FDA-approved endografts in our facility from July 2004 to December 2017. Patients were grouped into 3 cohorts based on preoperative aneurysm size: Group I (<5.5 cm), Group II (5.5-6.4 cm), and Group III (≥ 6.5 cm). Occurrences of endoleak, secondary intervention and overall survival underwent univariate and multivariate analysis. Cause of death data on deceased patients was similarly examined. RESULTS: A total of 517 patients were analyzed. There was no difference between size groups in the rate of endoleak (Group I 48/277, 17.3%; Group II 33/160, 20.6%; Group III 18/80, 22.5%; p = 0.46) or time until endoleak development. Univariate analysis showed no difference in the rate of secondary intervention (Group I 36/277, 13.0%; Group II 24/160, 15.0%; Group III 18/80, 22.5%; p = 0.11), time until intervention or number of interventions performed. Multivariate analysis showed an association with shorter time to secondary intervention for both Group III aneurysms (HR 2.03, 95% CI 1.11-3.73; p = 0.02) and female patients (HR 1.79, 95% CI 1.02-3.13; p = 0.04). There was no difference in overall survival, aneurysm-related mortality or overall cause of mortality. CONCLUSION: AAA diameter prior to EVAR was not associated with any differences in rates of endoleak or secondary intervention, and was not associated with poorer overall survival or greater aneurysm-related mortality. Patients with suitable anatomy for EVAR can be considered for this intervention without concern for increased complications or poorer outcomes related to large aneurysm diameter alone.

Bonding strengths to porcelain: An in vitro study of ultrasonic and conventional tooth preparation and etching.

OBJECTIVE: To compare the bond strength of porcelain to enamel and dentin preparations finished with either ultrasonic instruments or diamond burs, with or without acid etching. MATERIALS AND METHODS: A total of 140 extracted bovine incisor teeth were divided into two groups, enamel and dentin. A split tooth model was employed: each tooth having a randomly allocated combination of diamond burs, ultrasonic instrument, etching, and no etching treatments on their labial surface. Lithium disilicate glass ceramic specimens were bonded to the prepared surfaces and tensile testing was carried out. Force was applied to failure, and linear mixed models were used to analyze the data. RESULTS: Etching increased the bond strength of the dentin samples by 7.63 MPa (P < 0.001). When bonding to dentin, ultrasonic instrument preparation produced a 2.88 MPa greater bond strength compared to burs (P < 0.001). CONCLUSION: Ultrasonic preparation produced greater bond strengths compared to rotary instruments. Etching improved the bond strength of all preparations, with enamel having consistently greater bonding values than dentin.

Coil embolization of an acutely expanding spontaneous splenic artery dissection.

Symptomatic dilation of a spontaneous splenic artery dissection is a very rare and potentially catastrophic nonatherosclerotic vascular disease. Splenic artery rupture has not been reported after acute diffuse dilation, but it has been reported with celiac artery dissections. We believe treatment is mandatory if pain persists despite blood pressure control. The presentation and endovascular treatment of a spontaneous celiac trunk dissection with continued expansion of the splenic artery branch are discussed.

Elemental and isotopic behaviour of Zn in Deccan basalt weathering profiles: Chemical weathering from bedrock to laterite and links to Zn deficiency in tropical soils.

Zinc (Zn) is a micronutrient for organisms and essential for plant growth, therefore knowledge of its elemental cycling in the surface environment is important regarding wider aspects of human nutrition and health. To explore the nature of Zn cycling, we compared its weathering behaviour in a sub-recent regolith versus an ancient laterite profile of the Deccan Traps, India - an area of known soil Zn deficiency. We demonstrate that progressive breakdown of primary minerals and the associated formation of phyllosilicates and iron oxides leads to a depletion in Zn, ultimately resulting in a loss of 80% in lateritic residues. This residue is mainly composed of resistant iron oxides and hydroxides ultimately delivering insufficient amounts of bio-available Zn. Moreover, (sub)-tropical weathering in regions experiencing extended tectonic quiescence (e.g., cratons) further enhance the development of old and deep soil profiles that become deficient in Zn. This situation is clearly revealed by the spatial correlation of the global distribution of laterites, cratons (Africa, India, South America and Australia) and known regions of Zn deficient soils that result in health problems for humans whose diet is derived from such land. We also investigate whether this elemental depletion of Zn is accompanied by isotope fractionation. In the saprolitic horizons of both weathering profiles, compositions of δ66ZnJMC-Lyon lie within the "crustal average" of +0.27±0.07‰ δ66ZnJMC-Lyon. By contrast, soil horizons enriched in secondary oxides show lighter isotope compositions. The isotopic signature of Zn (Δ66Znsample-protolith up to ~ -0.65‰) during the formation of the ferruginous-lateritic weathering profile likely resulted from a combination of biotically- and kinetically-controlled sorption reactions on Fe-oxyhydroxides. Our findings suggest that oxide rich soil types/horizons in (sub)-tropical regions likely exert a control on riverine Zn isotope compositions such that these become heavier than the crustal average. This isotopic behaviour invites a broader study of global soils to test whether light isotope composition alone could serve as an indicator for reduced bioavailability of Zn.

AT excursion: a new approach to predict replication origins in viral genomes by locating AT-rich regions.

BACKGROUND: Replication origins are considered important sites for understanding the molecular mechanisms involved in DNA replication. Many computational methods have been developed for predicting their locations in archaeal, bacterial and eukaryotic genomes. However, a prediction method designed for a particular kind of genomes might not work well for another. In this paper, we propose the AT excursion method, which is a score-based approach, to quantify local AT abundance in genomic sequences and use the identified high scoring segments for predicting replication origins. This method has the advantages of requiring no preset window size and having rigorous criteria to evaluate statistical significance of high scoring segments. RESULTS: We have evaluated the AT excursion method by checking its predictions against known replication origins in herpesviruses and comparing its performance with an existing base weighted score method (BWS1). Out of 43 known origins, 39 are predicted by either one or the other method and 26 origins are predicted by both. The excursion method identifies six origins not predicted by BWS1, showing that the AT excursion method is a valuable complement to BWS1. We have also applied the AT excursion method to two other families of double stranded DNA viruses, the poxviruses and iridoviruses, of which very few replication origins are documented in the public domain. The prediction results are made available as supplementary materials at 1. Preliminary investigation shows that the proposed method works well on some larger genomes too. CONCLUSION: The AT excursion method will be a useful computational tool for identifying replication origins in a variety of genomic sequences.

Scoring schemes of palindrome clusters for more sensitive prediction of replication origins in herpesviruses.

Many empirical studies show that there are unusual clusters of palindromes, closely spaced direct and inverted repeats around the replication origins of herpesviruses. In this paper, we introduce two new scoring schemes to quantify the spatial abundance of palindromes in a genomic sequence. Based on these scoring schemes, a computational method to predict the locations of replication origins is developed. When our predictions are compared with 39 known or annotated replication origins in 19 herpesviruses, close to 80% of the replication origins are located within 2% of the genome length. A list of predicted locations of replication origins in all the known herpesviruses with complete genome sequences is reported.