Optimizing trigger timing in minimal ovarian stimulation for In Vitro fertilization using machine learning models with random search hyperparameter tuning.

Various studies have emphasized the importance of identifying the optimal Trigger Timing (TT) for the trigger shot in In Vitro Fertilization (IVF), which is crucial for the successful maturation and release of oocytes, especially in minimal ovarian stimulation treatments. Despite its significance for the ultimate success of IVF, determining the precise TT remains a complex challenge for physicians due to the involvement of multiple variables. This study aims to enhance TT by developing a machine learning multi-output model that predicts the expected number of retrieved oocytes, mature oocytes (MII), fertilized oocytes (2 PN), and useable blastocysts within a 48-h window after the trigger shot in minimal stimulation cycles. By utilizing this model, physicians can identify patients with possible early, late, or on-time trigger shots. The study found that approximately 27 % of treatments administered the trigger shot on a suboptimal day, but optimizing the TT using the developed Artificial Intelligence (AI) model can potentially increase useable blastocyst production by 46 %. These findings highlight the potential of predictive models as a supplementary tool for optimizing trigger shot timing and improving IVF outcomes, particularly in minimal ovarian stimulation. The experimental results underwent statistical validation, demonstrating the accuracy and performance of the model. Overall, this study emphasizes the value of AI prediction models in enhancing TT and making the IVF process safer and more efficient.

Magnetic hysteresis mechanism in Lu0.9Sr0.1Cr0.5Fe0.5O3studied by Monte Carlo simulations.

In this work we report magnetic properties of the orthorhombic perovskite Lu0.9Sr0.1Cr0.5Fe0.5O3synthesized by a wet chemical method. As in LuCr0.5Fe0.5O3the compound with Sr shows the magnetization reversal phenomenon, but the magnetic order and the compensation temperature occur at higher temperatures. Interestingly, in M vs H curves a hysteresis loop is observed when Cr4+and Cr3+ions coexist as a consequence of the aliovalent substitution of Lu3+by Sr2+in the B sites of the perovskite. To explain this behavior, we performed numerical simulations with a magnetic model for Lu1-xSrxCr0.5Fe0.5O3perovskites withx= 0 andx= 0.1. We found that the ferromagnetic coupling of Fe3+and Cr4+through superexchange interactions (according the empiric Goodenough-Kanamori-Anderson rules) increases the magnetization at high fields and that the presence of ferromagnetic clusters explains the hysteretic behavior found in simulations.

A Pliocene-Pleistocene continental biota from Venezuela.

The Pliocene-Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86Sr/88Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.

A stem delphinidan from the Caribbean region of Venezuela.

The dense Miocene record of cetaceans is known from localities along the coasts of all continents, mostly in the northern Atlantic or the eastern Pacific regions, but Antarctica. Fossils from the Caribbean region are few and include of a couple of findings from Panama and Venezuela. Here, we report a partly complete skull from the Caujarao Formation (middle Miocene), Falcon State, Caribbean region of Venezuela. Our phylogenetic analyses indicate that the Caujarao specimen is a 'stem delphinidan', a group that includes several taxa of early diverging odontocetes whose phylogenetic affinities remain a matter of debate. The fossil record has shown that this group of stem delphinidans was taxonomically diverse, but displayed a somewhat homogeneous cranial patterning, with most of the variations being found within the mandible or tympanoperiotic characters. As other stem delphinidans the Caujarao odontocete displays an enlarged temporal fossa and a fairly symmetrical cranium. Because the skull is missing several key diagnostic characters due to the preservation state of the specimen, a more precise taxonomic identification is not possible. Despite this, the finding of this specimen highlights the importance of the fossil record from the Neogene of Venezuela, and the importance of the area to understand cetacean evolution in the proto-Caribbean.

Predicting pregnancy test results after embryo transfer by image feature extraction and analysis using machine learning.

Assessing the viability of a blastosyst is still empirical and non-reproducible nowadays. We developed an algorithm based on artificial vision and machine learning (and other classifiers) that predicts pregnancy using the beta human chorionic gonadotropin (b-hCG) test from both the morphology of an embryo and the age of the patients. We employed two high-quality databases with known pregnancy outcomes (n = 221). We created a system consisting of different classifiers that is feed with novel morphometric features extracted from the digital micrographs, along with other non-morphometric data to predict pregnancy. It was evaluated using five different classifiers: probabilistic bayesian, Support Vector Machines (SVM), deep neural network, decision tree, and Random Forest (RF), using a k-fold cross validation to assess the model's generalization capabilities. In the database A, the SVM classifier achieved an F1 score of 0.74, and AUC of 0.77. In the database B the RF classifier obtained a F1 score of 0.71, and AUC of 0.75. Our results suggest that the system is able to predict a positive pregnancy test from a single digital image, offering a novel approach with the advantages of using a small database, being highly adaptable to different laboratory settings, and easy integration into clinical practice.

Estrategia combinada en fertilización in vitro: mínima estimulación y transferencia de embrión único con diagnóstico genético. Experiencia de 3 años en dos centros de reproducción en México / A combined in-vitro fertilization strategy: minimal stimulation IVF, PGT-A and SET. Results from 3 years' experience at two IVF centers in Mexico

Resumen OBJETIVO: Evaluar los desenlaces de una estrategia combinada para fertilización in vitro: mínima estimulación ovárica, diagnóstico genético preimplantación para aneuploidias y transferencia de un solo embrión. MATERIALES Y MÉTODOS: Estudio de cohorte, retrospectivo, efectuado en dos centros de reproducción de México, en un periodo de tres años. Se incluyeron pacientes entre 25 y 45 años, en protocolo de fertilización in vitro, con mínima estimulación, diagnóstico genético preimplantación para aneuploidias (PGT-A) y transferencia de embrión único. El diagnóstico genético preimplantación se estableció mediante microarreglos y secuenciación de nueva generación (NGS). Para el análisis estadístico se integraron 5 grupos, según la edad de las pacientes: menores de 35 años; 35 a 37 años; 38 a 40 años; 41 a 42 años; y mayores de 42 años. Mediante estadística descriptiva se analizaron las variables numéricas y categóricas. RESULTADOS: Se analizaron 175 ciclos, en 125 pacientes (edad promedio: 39 años ± 5). Se obtuvieron, en promedio, 5 óvulos por ciclo. La tasa de fertilización fue de 86.5% y la de blastocisto por óvulo fertilizado de 50.7%. Se tomó biopsia para diagnóstico genético preimplantación para aneuploidias a 404 embriones. La tasa general de euploidia fue de 33%. Se efectuaron 69 transferencias de embrión único, con una tasa de embarazo por transferencia de 71%. La tasa de nacimiento por transferencia fue de 60.8% (42 nacimientos). CONCLUSIONES: La combinación de mínima estimulación, diagnóstico genético preimplantación para aneuploidias y transferencia de embrión único, es un procedimiento adecuado para alcanzar una tasa de nacimiento alta.

Abstract OBJECTIVE: To evaluate results of a combined approach in IVF, using minimal stimulation, preimplantation genetic testing for aneuploidy, and single blastocyst transfer. MATERIALS AND METHODS: Retrospective cohort study over a three years' period in two fertility centers in Mexico. A total of 125 patients were included, between 25 and 45 years old, with minimal stimulation IVF, preimplantation genetic testing for aneuploidy (PGT-A) and single euploid embryo transfer. PGT was performed using microarrays and next generation sequencing (NGS). RESULTS: A total of 175 cycles (mean age: 39 years old) were analyzed in 125 patients. On average, five eggs were collected per cycle; fertilization rate was 86.57%; blastocyst rate was 50.7% per fertilized egg. Only 33% of embryos were euploid. Pregnancy rate per transferred embryo was 71%. Live birth rate was 60.8% (42 births). CONCLUSIONS: A combination of minimal stimulation, PGT-A and single blastocyst embryo transfer can yield a high live birth rate.

Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians.

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support.

Comparison of Total Anaerobic Microbiota in Periodontitis Before and After the Subgingival Irrigation with Chlorhexidine at 0. 12 % / Comparación de la Microbiota Anaerobia Total en Periodontitis antes y Después de la Irrigación Subgingival con Clorhexidina al 0, 12 %

ABSTRACT: The objective of this study was to determine the effect of the subgingival irrigation of chlorhexidine 0.12 % of the total anaerobic microbiota. Microbial sampling to 30 subjects with periodontitis stage II Grade B, in pockets with a periodontal probing depth > 4 mm. The subgingival irrigation was made with 5 mL of chlorhexidine in the test group and with 5 mL of distilled water in the control group. 24 hours after the procedure was obtained a second sample to compare. It was found that the subgingival irrigation with chlorhexidine at 0.12 % achieved a statistically significant decrease in anaerobic microbiota (p< 0.05).

RESUMEN: El objetivo del presente estudio fue determinar el efecto de la irrigación subgingival de la clorhexidina 0,12 % sobre la microbiota anaeróbica total. Se tomaron muestras microbiológicas a 30 sujetos con periodontitis estadio II grado B, en sacos periodontales con una profundidad de sondaje > 4 mm. Se realizó la irrigación subgingival con 5 mL. de clorhexidina en el grupo test y con 5 mL. de agua destilada en el grupo control. 24 horas después del procedimiento se obtuvo una segunda muestra a comparar. Se detectó que la irrigación subgingival con clorhexidina al 0,12 % logra disminuir en forma estadísticamente significativa la microbiota anaeróbica total (p< 0,05).

Aging effect on vanadium oxide hybrid nanotubes.

Vanadium oxides present a rich magnetic phase diagram depending on the oxidation state of the V ions. In particular the vanadium oxide nanotubes (VO x NTs) present several promising perspectives for different technological applications for which it is essential to know the oxidation state of V ions, as well as to evaluate the stability with the aging time of the tubes. In this work we present a systematic study of the time evolution of the magnetic properties of VO x NTs. For this complete characterization, we used electron spin resonance (ESR) and dc-susceptibility techniques, which were supplemented with TEM microscopy and XANES. We observed that for aging in normal environmental conditions of pressure, temperature and humidity, the V4+ ions oxidize to V5+ . Although the multiwall tubular structure is maintained, this oxidation process produces a marked change in the magnetic properties. We conclude that the aging of the samples affects the V4+ /V5+ relationship in the VO x NTs, which may contribute to explain the significant dispersion of data reported in the bibliography.

Prevalence of Aves Polyomavirus 1 and Beak and Feather Disease Virus From Exotic Captive Psittacine Birds in Chile.

Avian polyomavirus disease and psittacine beak and feather disease (PBFD) are both contagious viral diseases in psittacine birds with similar clinical manifestations and characterized by abnormal feathers. To determine the prevalence of Aves polyomavirus 1 (APyV) and beak and feather disease virus (BFDV) in captive, exotic psittacine birds in Chile, feathers from 250 psittacine birds, representing 17 genera, were collected and stored during the period 2013-2016. Polymerase chain reaction testing was used to detect APyV and BFDV were detected in feather bulb samples. The results indicated that 1.6% (4/250) of the samples were positive for APyV, 23.2% (58/250) were positive to BFDV, and 0.8% (2/250) were positive to both APyV and BFDV. This is the first report, to our knowledge, of APyV and BFDV prevalence in captive, exotic psittacine birds in South America. Analysis of 2 Chilean partial sequences of the gene encoding agnoprotein 1a (APyV) and the replication-associated protein (BFDV) extends the knowledge of genomic variability for both APyV and BFDV isolates and their spectrum of hosts. No geographical marker was detected for the local isolates.

Nuclear Charge Radii of

The first laser spectroscopic determination of the change in the nuclear charge radius for a five-electron system is reported. This is achieved by combining high-accuracy ab initio mass-shift calculations and a high-accuracy measurement of the isotope shift in the 2s^{2}2p ^{2}P_{1/2}→2s^{2}3s ^{2}S_{1/2} ground state transition in boron atoms. Accuracy is increased by orders of magnitude for the stable isotopes ^{10,11}B and the results are used to extract their difference in the mean-square charge radius ⟨r_{c}^{2}⟩^{11}-⟨r_{c}^{2}⟩^{10}=-0.49(12) fm^{2}. The result is qualitatively explained by a possible cluster structure of the boron nuclei and quantitatively used to benchmark new ab initio nuclear structure calculations using the no-core shell model and Green's function Monte Carlo approaches. These results are the foundation for a laser spectroscopic determination of the charge radius of the proton-halo candidate ^{8}B.

Tlif-mis vs tlif-open: cost evaluation / Tlif-mis vs tlif-open: evaluação de custos / Tlif mis vs tlif-open: evaluación de costos

ABSTRACT Objective: To evaluate the direct costs of transforaminal lumbar interbody fusion (TLIF) and minimally invasive surgery (MIS) or open technique (OPEN). Methods: The present study is descriptive and retrospective. Sixteen patients with degenerative spinal pathology operated on with the TLIF MIS technique and TLIF OPEN were included over a 13-month period. Days of hospital stay, blood loss, surgical time, medical care and costs were compared. Results: The mean number of days of hospital stay was 6.7 ± 4.3 days with TLIF MIS and 11.1 ± 6.5 days with TLIF OPEN. The blood loss was 307 ± 81.6 ml (range 200400 ml) with TLIF MIS and 803 ± 701.3 ml (range 200-1800 ml) with TLIF OPEN. The surgical time was 320 ± 92.6 minutes (range 210-500 minutes) in TLIF MIS and 372 ± 95.2 minutes (280-540 minutes) in TLIF OPEN. Conclusions: The difference in surgical costs and time between the two procedures was not statistically significant. There was less bleeding during the TLIF-MIS surgery, as well as a correlation between shorter days of hospital stay proportional to bleeding and surgical time, which translates into a reduction in the cost of these items. Level of Evidence III; Analysis based on alternatives and limited costs.

RESUMO Objetivo: Garantir benefícios económicos diretos de cada procedimento cirúrgico. Metodologia: apresentar um estudo descritivo e retrospectivo. Dezesseis pacientes com patologia degenerativa de colônias operados com a técnica TLIF MIS e TLIF OPEN foram incluídos durante um período de 13 meses. Foram comparados os dias de internação, perda de sangue, tempo cirúrgico, assistência médica e custo. Resultados: O número de dias hospitalares para 6,7 ± 4,3 dias no TLIF MIS e 11,1 ± 6,5 dias no TLIF OPEN. Quanto à diferença entre a exigência de resultados da imagem e o número de cirurgias. A perda de sangue foi de 307 ± 81,6 ml (intervalo de 200-400 ml) com TLIF MIS e 803 ± 701,3 ml (intervalo de 200 - 1800 ml) com TLIF OPEN. O tempo cirúrgico de 320 ± 92,6 minutos (intervalo 210-500 minutos) em TLIF MIS e 372 ± 95,2 minutos (280-540 minutos) em TLIF OPEN. Conclusões: A diferença entre os procedimentos cirúrgicos e o tempo entre os procedimentos não é estatisticamente significativa. Houve menos sangria durante a cirurgia do TLIF-MIS, assim como uma correlação entre menos dias de internação proporcional ao sangramento e ao tempo cirúrgico, que se traduziu em uma redução dos custos dos itens. Nível de Evidência III; Análise baseada em alternativas e custos limitados.

RESUMEN Objetivo: Evaluar los costos directos de la fusión intersomática lumbar transforaminal (TLIF) de mínima invasión (MIS) o técnica abierta (OPEN). Métodos: El presente estudio es descriptivo y retrospectivo. Se incluyeron 16 pacientes con patología degenerativa de columna intervenidos con la técnica TLIF MIS y TLIF OPEN en un período de 13 meses. Se compararon días de estancia hospitalaria, pérdida sanguínea, tiempo quirúrgico, atención médica y costos. Resultados: La media de días de estancia hospitalaria fue de 6,7 ± 4,3 días con TLIF MIS y de 11,1 ± 6,5 días con TLIF OPEN. La pérdida sanguínea fue de 307 ± 81,6 ml (rango 200-400 ml) con TLIF MIS y de 803 ± 701,3 ml (rango 200-1800 ml) con TLIF OPEN. El tiempo quirúrgico fue de 320 ± 92,6 minutos (rango 210-500 minutos) en TLIF MIS y de 372 ± 95,2 minutos (280-540 minutos) en TLIF OpEN. Conclusiones: La diferencia de costos y tiempo quirúrgico entre ambos procedimientos no fue estadísticamente significativa. Se mostró un menor sangrado durante la cirugía TLIF-MIS, así como una correlación entre menores días de estancia hospitalaria proporcional con el sangrado y tiempo quirúrgico, lo cual traduce una reducción del costo en esos rubros. Nivel de Evidencia III; Análisis basados en alternativas y costos limitados.

Physiological and molecular mechanisms underlying the integration of light and temperature cues in Arabidopsis thaliana seeds.

The relief of dormancy and the promotion of seed germination are of extreme importance for a successful seedling establishment. Although alternating temperatures and light are signals promoting the relief of seed dormancy, the underlying mechanisms of their interaction in seeds are scarcely known. By exposing imbibed Arabidopsis thaliana dormant seeds to two-day temperature cycles previous of a red light pulse, we demonstrate that the germination mediated by phytochrome B requires the presence of functional PSEUDO-RESPONSE REGULATOR 7 (PRR7) and TIMING OF CAB EXPRESSION 1 (TOC1) alleles. In addition, daily cycles of alternating temperatures in darkness reduce the protein levels of DELAY OF GERMINATION 1 (DOG1), allowing the expression of TOC1 to induce seed germination. Our results suggest a functional role for some components of the circadian clock related with the action of DOG1 for the integration of alternating temperatures and light signals in the relief of seed dormancy. The synchronization of germination by the synergic action of light and temperature through the activity of circadian clock might have ecological and adaptive consequences.

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED.

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

Association of obesity and overweight with the prevalence of insulin resistance, pre-diabetes and clinical-biochemical characteristics among infertile Mexican women with polycystic ovary syndrome: a cross-sectional study.

OBJECTIVE: To study the association of obesity and overweight with the prevalence of insulin resistance (IR), pre-diabetes and clinical-biochemical characteristics among infertile Mexican women with polycystic ovary syndrome (PCOS). DESIGN: Retrospective cross-sectional study. SETTING: Level-three medical institution, an infertility clinic in Mexico City. PARTICIPANTS: We included infertile Mexican women with diagnosis of PCOS according to the Rotterdam criteria: group 1 (n=83), normal weight (body mass index (BMI) 18.5-24.9 kg/m(2)); group 2 (n=217), overweight (BMI 25-29.9 kg/m(2)); and group 3 (n=238), obese (BMI≥30 kg/m(2)). PRIMARY AND SECONDARY OUTCOME MEASURES: IR was determined by homeostatic model assessment (HOMA) >2.5 and pre-diabetes by fasting glucose between 5.6 and 6.9 mmol/L and/or glucose value between 7.8 and 11 mmol/L at 2 hours during an oral glucose tolerance test. We compared clinical-biochemical characteristics among groups. RESULTS: Prevalence of IR for groups 1, 2 and 3 was 19.3%, 56.2% and 78.2%; overweight and obesity increase the IR OR (CI 95%) to 5.3 (2.9 to 9.8) and 14.9 (8.0 to 28), respectively. Prevalence of pre-diabetes for groups 1, 2 and 3 was 7.2%, 17.5% and 31.5%; overweight and obesity increase the pre-diabetes OR (CI 95%) to 2.7 (1.1 to 6.7) and 5.9 (2.4 to 14), respectively. Acanthosis nigricans was more frequent in group 3 than group 1. Free Androgen Index (FAI) and thyroid-stimulating hormone (TSH) levels were lower in group 1 than in groups 2 and 3. Progesterone and sex hormone-binding globulin (SHBG) levels were higher in group 1 than in groups 2 and 3. Dehydroepiandrosterone sulfate (DHEA-S) was higher in group 1 than group 3. CONCLUSIONS: Obese and overweight infertile Mexican women with PCOS, attending to an infertility clinic, have a higher prevalence of IR and pre-diabetes compared with normal-weight women with PCOS. Therapeutic interventions should include those that improved metabolic functioning prior to attempting pregnancy in these groups of women.

The CREB Transcription Factor Controls Transcriptional Activity of the Human RIC8B Gene.

Proper regulation of gene expression is essential for normal development, cellular growth, and differentiation. Differential expression profiles of mRNA coding for vertebrate Ric-8B during embryo and adult stages have been observed. In addition, Ric-8B is expressed in few cerebral nuclei subareas. These facts point to a dynamic control of RIC8B gene expression. In order to understand the transcriptional regulation of this gene, we searched for cis-elements in the sequence of the human RIC8B promoter region, identifying binding sites for the basic/leucine zipper (bZip) CREB transcription factor family (CRE sites) and C/EBP transcription factor family (C/EBP sites). CRE sites were found clustered near the transcription start site, while the C/EBP sites were found clustered at around 300 bp upstream the CRE sites. Here, we demonstrate the ability of CREB1 and C/EBPß to bind their respective elements identified in the RIC8B promoter. Comparative protein-DNA interaction analyses revealed only the proximal elements as high affinity sites for CREB1 and only the distal elements as high affinity sites for C/EBPß. Chromatin immunoprecipitation analyses, carried out using a human neuroblastoma cell line, confirmed the preferential association of CREB to the proximal region of the RIC8B promoter. By performing luciferase reporter assays, we found the CRE sites as the most relevant elements for its transcriptional activity. Taken together, these data show the existence of functional CREB and C/EBP binding sites in the human RIC8B gene promoter, a particular distribution of these sites and demonstrate a relevant role of CREB in stimulating transcriptional activity of this gene. J. Cell. Biochem. 117: 1797-1805, 2016. © 2016 Wiley Periodicals, Inc.

Seed dormancy responses to temperature relate to Nothofagus species distribution and determine temporal patterns of germination across altitudes in Patagonia.

Seeds integrate environmental cues that modulate their dormancy and germination. Although many mechanisms have been identified in laboratory experiments, their contribution to germination dynamics in existing communities and their involvement in defining species habitats remain elusive. By coupling mathematical models with ecological data we investigated the contribution of seed temperature responses to the dynamics of germination of three Nothofagus species that are sharply distributed across different altitudes in the Patagonian Andes. Seed responsiveness to temperature of the three Nothofagus species was linked to the thermal characteristics of their preferred ecological niche. In their natural distribution range, there was overlap in the timing of germination of the species, which was restricted to mid-spring. By contrast, outside their species distribution range, germination was temporally uncoupled with altitude. This phenomenon was described mathematically by the interplay between interspecific differences in seed population thermal parameters and the range in soil thermic environments across different altitudes. The observed interspecific variations in seed responsiveness to temperature and its environmental regulation, constitute a major determinant of the dynamics of Nothofagus germination across elevations. This phenomenon likely contributes to the maintenance of patterns of species abundance across altitude by placing germinated seeds in a favorable environment for plant growth.

Molecular mechanisms underlying the entrance in secondary dormancy of Arabidopsis seeds.

As seasons change, dormant seeds cycle through dormant states until the environmental conditions are favourable for seedling establishment. Dormancy cycle is widespread in the plant kingdom allowing the seeds to display primary and secondary dormancy. Several reports in the last decade have focused on understanding the molecular mechanisms of primary dormancy, but our knowledge regarding secondary dormancy is limited. Here, we studied secondary dormancy induced in Arabidopsis thaliana by incubating seeds at 25 °C in darkness for 4 d. By physiological, pharmacological, expression and genetics approaches, we demonstrate that (1) the entrance in secondary dormancy involves changes in the content and sensitivity to GA, but the content and sensitivity to ABA do not change, albeit ABA is required; (2) RGL2 promotes the entrance in secondary dormancy through ABI5 action; and (3) multivariate analysis with 18 geographical and environmental parameters of accession collection place suggests that temperature is an important variable influencing the induction of secondary dormancy in nature.

Sawfishes and Other Elasmobranch Assemblages from the Mio-Pliocene of the South Caribbean (Urumaco Sequence, Northwestern Venezuela).

The Urumaco stratigraphic sequence, western Venezuela, preserves a variety of paleoenvironments that include terrestrial, riverine, lacustrine and marine facies. A wide range of fossil vertebrates associated with these facies supports the hypothesis of an estuary in that geographic area connected with a hydrographic system that flowed from western Amazonia up to the Proto-Caribbean Sea during the Miocene. Here the elasmobranch assemblages of the middle Miocene to middle Pliocene section of the Urumaco sequence (Socorro, Urumaco and Codore formations) are described. Based on new findings, we document at least 21 taxa of the Lamniformes, Carcharhiniformes, Myliobatiformes and Rajiformes, and describe a new carcharhiniform species (†Carcharhinus caquetius sp. nov.). Moreover, the Urumaco Formation has a high number of well-preserved fossil Pristis rostra, for which we provide a detailed taxonomic revision, and referral in the context of the global Miocene record of Pristis as well as extant species. Using the habitat preference of the living representatives, we hypothesize that the fossil chondrichthyan assemblages from the Urumaco sequence are evidence for marine shallow waters and estuarine habitats.

Precision Test of Many-Body QED in the Be+ 2p Fine Structure Doublet Using Short-Lived Isotopes.

Absolute transition frequencies of the 2s 2S{1/2}→2p2P{1/2,3/2} transitions in Be^{+} were measured for the isotopes ^{7,9-12}Be. The fine structure splitting of the 2p state and its isotope dependence are extracted and compared to results of ab initio calculations using explicitly correlated basis functions, including relativistic and quantum electrodynamics effects at the order of mα(6) and mα(7) ⁢ln α. Accuracy has been improved in both the theory and experiment by 2 orders of magnitude, and good agreement is observed. This represents one of the most accurate tests of quantum electrodynamics for many-electron systems, being insensitive to nuclear uncertainties.