5,633 research outputs found
Exobiology and the search for biological signatures on Mars
In preparation for a Mars Rover/Sample return mission, the mission goals and objectives must be identified. One of the most important objectives must address exobiology and the question of the possibility of the origin and evolution of life on Mars. In particular, key signatures or bio-markers of a possible extinct Martian biota must be defined. To that end geographic locations (sites) that are likely to contain traces of past life must also be identified. Sites and experiments are being defined in support of a Mars rover sample return mission. In addition, analyses based on computer models of abiotic processes of CO2 loss from Mars suggest that the CO2 from the atmosphere may have precipitated as carbonates and be buried within the Martian regolith. The carbon cycle of perennially frozen lakes in the dry valley of Antarctica are currently being investigated. These lakes were purported to be a model system for the ancient Martian lakes. By understanding the dynamic balance between the abiotic vs. biotic cycling of carbon within this system, information is gathered which will enable the interpretation of data obtained by a Mars rover with respect to possible carbonate deposits and the processing of carbon by biological systems. These ancient carbonate deposits, and other sedimentary units would contain traces of biological signatures that would hold the key to understanding the origin and evolution of life on Mars, as well as Earth
Nonadditivity of intermolecular forces - Effects on the third virial coefficient
Effects of nonadditive three body forces on third virial coefficien
Primary mediastinal lymphoma: diagnosis and treatment options.
Primary mediastinal large B-cell lymphoma (PMBCL) is a unique B-cell lymphoma variant that arises from a putative thymic medulla B cell. It constitutes 2-4% of non-Hodgkin lymphomas and occurs most frequently in young females. PMBCL is characterized by a diffuse proliferation of medium-to-large B cells associated with sclerosis. Molecular analysis shows that PMBCL is a distinct entity compared to other types of diffuse large B-cell lymphomas. PMBCL is characterized by a locally invasive anterior mediastinal bulky mass. The combination of rituximab with CHOP/CHOP-like regimens followed by mediastinal radiation therapy (RT) is associated with a 5-year progression-free survival of 75-85%. However, the role of consolidation RT still remains uncertain. More intensive regimens, such as DA-EPOCH-R without mediastinal RT, have shown very promising results. The conclusive role of PET-CT scan requires prospective studies and there is hope that this may allow to de-escalate RT and accordingly yield reliable prognostic information
A Frobenius variant of Seshadri constants
We define and study a version of Seshadri constant for ample line bundles in
positive characteristic. We prove that lower bounds for this constant imply the
global generation or very ampleness of the corresponding adjoint line bundle.
As a consequence, we deduce that the criterion for global generation and very
ampleness of adjoint line bundles in terms of usual Seshadri constants holds
also in positive characteristic.Comment: 16 page
Temperature-sensitive protein–DNA dimerizers
Programmable DNA-binding polyamides coupled to short peptides have led to the creation of synthetic artificial transcription factors. A hairpin polyamide-YPWM tetrapeptide conjugate facilitates the binding of a natural transcription factor Exd to an adjacent DNA site. Such small molecules function as protein-DNA dimerizers that stabilize complexes at composite DNA binding sites. Here we investigate the role of the linker that connects the polyamide to the peptide. We find that a substantial degree of variability in the linker length is tolerated at lower temperatures. At physiological temperatures, the longest linker tested confers a "switch"-like property on the protein-DNA dimerizer, in that it abolishes the ability of the YPWM moiety to recruit the natural transcription factor to DNA. These observations provide design principles for future artificial transcription factors that can be externally regulated and can function in concert with the cellular regulatory circuitry
Response to. comment on optic nerve sheath diameter ultrasound evaluation in intensive care unit: possible role and clinical aspects in neurological critical patients' daily monitoring
Comment on "Optic Nerve Sheath Diameter Ultrasound Evaluation in Intensive Care Unit: Possible Role and Clinical Aspects in Neurological Critical Patients' Daily Monitoring"
Limited versus extended pelvic lymphadenectomy during robot-assisted radical prostatectomy: impact on the number of nodes and on nodal invasion
Genetic Features of Metachronous Esophageal Cancer Developed in Hodgkin's Lymphoma or Breast Cancer Long-Term Survivors: An Exploratory Study.
Background
Development of novel therapeutic drugs and regimens for cancer treatment has led to improvements in patient long-term survival. This success has, however, been accompanied by the increased occurrence of second primary cancers. Indeed, patients who received regional radiotherapy for Hodgkin's Lymphoma (HL) or breast cancer may develop, many years later, a solid metachronous tumor in the irradiated field. Despite extensive epidemiological studies, little information is available on the genetic changes involved in the pathogenesis of these solid therapy-related neoplasms.
Methods
Using microsatellite markers located in 7 chromosomal regions frequently deleted in sporadic esophageal cancer, we investigated loss of heterozygosity (LOH) and microsatellite instability (MSI) in 46 paired (normal and tumor) samples. Twenty samples were of esophageal carcinoma developed in HL or breast cancer long-term survivors: 14 squamous cell carcinomas (ESCC) and 6 adenocarcinomas (EADC), while 26 samples, used as control, were of sporadic esophageal cancer (15 ESCC and 11 EADC).
Results
We found that, though the overall LOH frequency at the studied chromosomal regions was similar among metachronous and sporadic tumors, the latter exhibited a statistically different higher LOH frequency at 17q21.31 (p = 0.018). By stratifying for tumor histotype we observed that LOH at 3p24.1, 5q11.2 and 9p21.3 were more frequent in ESCC than in EADC suggesting a different role of the genetic determinants located nearby these regions in the development of the two esophageal cancer histotypes.
Conclusions
Altogether, our results strengthen the genetic diversity among ESCC and EADC whether they occurred spontaneously or after therapeutic treatments. The presence of histotype-specific alterations in esophageal carcinoma arisen in HL or breast cancer long-term survivors suggests that their transformation process, though the putative different etiological origin, may retrace sporadic ESCC and EADC carcinogenesis
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