Melting in the Earth's deep upper mantle caused by carbon dioxide

The onset of partial melting beneath mid-ocean ridges governs the cycling of highly incompatible elements from the mantle to the crust, the flux of key volatiles (such as CO2, He and Ar) and the rheological properties of the upper mantle. Geophysical observations indicate that melting beneath ridges begins at depths approaching 300 km, but the cause of this melting has remained unclear. Here we determine the solidus of carbonated peridotite from 3 to 10 GPa and demonstrate that melting beneath ridges may occur at depths up to 330 km, producing 0.03-0.3% carbonatite liquid. We argue that these melts promote recrystallization and realignment of the mineral matrix, which may explain the geophysical observations. Extraction of incipient carbonatite melts from deep within the oceanic mantle produces an abundant source of metasomatic fluids and a vast mantle residue depleted in highly incompatible elements and fractionated in key parent-daughter elements. We infer that carbon, helium, argon and highly incompatible heat-producing elements (such as uranium, thorium and potassium) are efficiently scavenged from depths of approximately 200-330 km in the upper mantle.     

Thallium isotopic evidence for ferromanganese sediments in the mantle source of Hawaiian basalts

Ocean island basalts are generally thought to be the surface expression of mantle plumes, but the nature of the components in the source regions of such mantle plumes is a subject of long-standing debate. The lavas erupted at Hawaii have attracted particular attention, as it has been proposed that coupled 186Os and 187Os anomalies reflect interaction with the Earth's metallic core. It has recently been suggested, however, that such variations could also result from addition of oceanic ferromanganese sediments to the mantle source of these lavas. Here we show that Hawaiian picrites with osmium isotope anomalies also exhibit pronounced thallium isotope variations, which are coupled with caesium/thallium ratios that extend to values much lower than commonly observed for mantle-derived rocks. This correlation cannot be created by admixing of core material, and is best explained by the addition of ferromanganese sediments into the Hawaii mantle source region. However, the lack of correlation between thallium and osmium isotopes and the high thallium/osmium ratios of ferromanganese sediments preclude a sedimentary origin for the osmium isotope anomalies, and leaves core-mantle interaction as a viable explanation for the osmium isotope variations of the Hawaiian picrites.     

Role for DNA methylation in the control of cell type specific maspin expression

The major histocompatibility complex (MHC) is a source of unique individual odors that influence individual recognition, mating preferences, nesting behavior and selective block of pregnancy in animals. Such phenomena have been difficult to study in humans, because the human leukocyte antigen (HLA, human MHC) loci are the most polymorphic loci in the human genome, with the potential to generate millions of unique combinations of genotypes. In addition, high variability in background odors, encoded by the rest of the genome and influenced by cultural practices, contribute to a low signal-to-noise ratio that could mask HLA-based olfactory cues. Here we show that women can detect differences of one HLA allele among male odor donors with different MHC genotypes. Notably, the mechanism for a woman's ability to discriminate and choose odors is based on HLA alleles inherited from her father but not her mother. The parents' HLA alleles that she does not inherit show no relationship with odor choice, despite exposure to these HLA-encoded odors throughout her life. Our data indicate that paternally inherited HLA-associated odors influence odor preference and may serve as social cues.     

Gene expression profiling predicts clinical outcome of breast cancer

Breast cancer patients with the same stage of disease can have markedly different treatment responses and overall outcome. The strongest predictors for metastases (for example, lymph node status and histological grade) fail to classify accurately breast tumours according to their clinical behaviour. Chemotherapy or hormonal therapy reduces the risk of distant metastases by approximately one-third; however, 70-80% of patients receiving this treatment would have survived without it. None of the signatures of breast cancer gene expression reported to date allow for patient-tailored therapy strategies. Here we used DNA microarray analysis on primary breast tumours of 117 young patients, and applied supervised classification to identify a gene expression signature strongly predictive of a short interval to distant metastases ('poor prognosis' signature) in patients without tumour cells in local lymph nodes at diagnosis (lymph node negative). In addition, we established a signature that identifies tumours of BRCA1 carriers. The poor prognosis signature consists of genes regulating cell cycle, invasion, metastasis and angiogenesis. This gene expression profile will outperform all currently used clinical parameters in predicting disease outcome. Our findings provide a strategy to select patients who would benefit from adjuvant therapy.     

BH3-only Bcl-2 family member Bim is required for apoptosis of autoreactive thymocytes

During lymphocyte development, the assembly of genes coding for antigen receptors occurs by the combinatorial linking of gene segments. The stochastic nature of this process gives rise to lymphocytes that can recognize self-antigens, thereby having the potential to induce autoimmune disease. Such autoreactive lymphocytes can be silenced by developmental arrest or unresponsiveness (anergy), or can be deleted from the repertoire by cell death. In the thymus, developing T lymphocytes (thymocytes) bearing a T-cell receptor (TCR)-CD3 complex that engages self-antigens are induced to undergo programmed cell death (apoptosis), but the mechanisms ensuring this 'negative selection' are unclear. We now report that thymocytes lacking the pro-apoptotic Bcl-2 family member Bim (also known as Bcl2l11) are refractory to apoptosis induced by TCR-CD3 stimulation. Moreover, in transgenic mice expressing autoreactive TCRs that provoke widespread deletion, Bim deficiency severely impaired thymocyte killing. TCR ligation upregulated Bim expression and promoted interaction of Bim with Bcl-XL, inhibiting its survival function. These findings identify Bim as an essential initiator of apoptosis in thymocyte-negative selection.     

Catastrophic ape decline in western equatorial Africa

Because rapidly expanding human populations have devastated gorilla (Gorilla gorilla) and common chimpanzee (Pan troglodytes) habitats in East and West Africa, the relatively intact forests of western equatorial Africa have been viewed as the last stronghold of African apes. Gabon and the Republic of Congo alone are thought to hold roughly 80% of the world's gorillas and most of the common chimpanzees. Here we present survey results conservatively indicating that ape populations in Gabon declined by more than half between 1983 and 2000. The primary cause of the decline in ape numbers during this period was commercial hunting, facilitated by the rapid expansion of mechanized logging. Furthermore, Ebola haemorrhagic fever is currently spreading through ape populations in Gabon and Congo and now rivals hunting as a threat to apes. Gorillas and common chimpanzees should be elevated immediately to 'critically endangered' status. Without aggressive investments in law enforcement, protected area management and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction.     

Gremlin is the BMP antagonist required for maintenance of Shh and Fgf signals during limb patterning

During limb outgrowth, signaling by bone morphogenetic proteins (BMPs) must be moderated to maintain the signaling loop between the zone of polarizing activity (ZPA) and the apical ectodermal ridge (AER). Gremlin, an extracellular Bmp antagonist, has been proposed to fulfill this function and therefore be important in limb patterning. We tested this model directly by mutating the mouse gene encoding gremlin (Cktsf1b1, herein called gremlin). In the mutant limb, the feedback loop between the ZPA and the AER is interrupted, resulting in abnormal skeletal pattern. We also show that the gremlin mutation is allelic to the limb deformity mutation (ld). Although Bmps and their antagonists have multiple roles in limb development, these experiments show that gremlin is the principal BMP antagonist required for early limb outgrowth and patterning.     

Approximation of NURBS Curves and Surfaces Using Adaptive Equidistant Parameterizations

Introduction Curves and surfaces can be represented using coefficients and a set of basis functions[1]. In the following, only curves are considered, but all statements apply equally to surfaces. Different representations use different sets of basis functions. These basis functions can be, for example, polynomials for polynomial curves, Bernstein-polynomials for Bézier curves, or B-spline basis functions for B-spline curves. As long as the general representation is of the form: 0( ) ( )ni i…