43,460 research outputs found
Violation of Kohler's rule by the magnetoresistance of a quasi-two-dimensional organic metal
The interlayer magnetoresistance of the quasi-two-dimensional metal
-(BEDT-TTF)KHg(SCN) is considered. In the temperature range
from 0.5 to 10 K and for fields up to 10 tesla the magnetoresistance has a
stronger temperature dependence than the zero-field resistance. Consequently
Kohler's rule is not obeyed for any range of temperatures or fields. This means
that the magnetoresistance cannot be described in terms of semiclassical
transport on a single Fermi surface with a single scattering time. Possible
explanations for the violations of Kohler's rule are considered, both within
the framework of semi-classical transport theory and involving incoherent
interlayer transport. The issues considered are similar to those raised by the
magnetotransport of the cuprate superconductors.Comment: 5 pages, RevTeX + epsf, 2 figures. Slightly revised version to appear
in Physical Review B, May 15, 199
Spin-triplet superconductivity in a weak-coupling Hubbard model for the quasi-one-dimensional compound LiMoO
The purple bronze LiMoO is of interest due to its
quasi-one-dimensional electronic structure and the possible Luttinger liquid
behavior resulting from it. For sufficiently low temperatures, it is a
superconductor with a pairing symmetry that is still to be determined. To shed
light on this issue, we analyze a minimal Hubbard model for this material
involving four molybdenum orbitals per unit cell near quarter filling, using
asymptotically exact perturbative renormalization group methods. We find that
spin triplet odd-parity superconductivity is the dominant instability.
Approximate nesting properties of the two quasi-one-dimensional Fermi surfaces
enhance certain second-order processes, which play crucial roles in determining
the structure of the pairing gap. Notably, we find that the gap has accidental
nodes, i.e. it has more sign changes than required by the point-group symmetry.Comment: Update
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Animals bearing malignant grafts reject normal grafts that express through gene transfer the same antigen.
Breaking the state of immunological unresponsiveness of tumor-bearing individuals to cancer is a prerequisite for active or passive tumor-specific immunotherapy. To study this problem the immunogenic MHC class I antigen, K216 was transfected into a progressor tumor. The transfected tumors were regularly rejected by normal mice but grew progressively in mice bearing nontransfected tumors. In addition, transgenic mice were derived to obtain normal cells and tissues expressing the same K216 gene product. Normal mice rejected K216-positive normal or malignant tissue grafts and generated K216-specific CTL in vitro and in vivo in response to these challenges. In contrast, mice bearing nontransfected tumors, though rejecting K216-positive nonmalignant tissue grafts, did not reject K216-positive tumors nor generate K216-specific CTL in response to K216-positive tumor cells. Mice bearing K216-positive tumors also rejected the nonmalignant K216-positive tissue grafts, but this in vivo response failed to lead to rejection of the simultaneously present tumor graft expressing the same antigen; in fact, immunity had no measurable effect whatsoever on tumor size or incidence and caused no selection for antigen loss variants. Taken together, the present findings suggest that transfer of expression of a target antigen into nonmalignant cells provides a way for obtaining effective stimulation of antigen-specific CTL in tumor-bearing mice, but that additional manipulations will be required to cause immunological rejection of established tumors
Bringing self assessment home: repository profiling and key lines of enquiry within DRAMBORA
Digital repositories are a manifestation of complex organizational, financial, legal, technological, procedural, and political interrelationships. Accompanying each of these are innate uncertainties, exacerbated by the relative immaturity of understanding prevalent within the digital preservation domain. Recent efforts have sought to identify core characteristics that must be demonstrable by successful digital repositories, expressed in the form of check-list documents, intended to support the processes of repository accreditation and certification. In isolation though, the available guidelines lack practical applicability; confusion over evidential requirements and difficulties associated with the diversity that exists among repositories (in terms of mandate, available resources, supported content and legal context) are particularly problematic. A gap exists between the available criteria and the ways and extent to which conformity can be demonstrated. The Digital Repository Audit Method Based on Risk Assessment (DRAMBORA) is a methodology for undertaking repository self assessment, developed jointly by the Digital Curation Centre (DCC) and DigitalPreservationEurope (DPE). DRAMBORA requires repositories to expose their organization, policies and infrastructures to rigorous scrutiny through a series of highly structured exercises, enabling them to build a comprehensive registry of their most pertinent risks, arranged into a structure that facilitates effective management. It draws on experiences accumulated throughout 18 evaluative pilot assessments undertaken in an internationally diverse selection of repositories, digital libraries and data centres (including institutions and services such as the UK National Digital Archive of Datasets, the National Archives of Scotland, Gallica at the National Library of France and the CERN Document Server). Other organizations, such as the British Library, have been using sections of DRAMBORA within their own risk assessment procedures.
Despite the attractive benefits of a bottom up approach, there are implicit challenges posed by neglecting a more objective perspective. Following a sustained period of pilot audits undertaken by DPE, DCC and the DELOS Digital Preservation Cluster aimed at evaluating DRAMBORA, it was stated that had respective project members not been present to facilitate each assessment, and contribute their objective, external perspectives, the results may have been less useful. Consequently, DRAMBORA has developed in a number of ways, to enable knowledge transfer from the responses of comparable repositories, and incorporate more opportunities for structured question sets, or key lines of enquiry, that provoke more comprehensive awareness of the applicability of particular threats and opportunities
Liability of a Carrier under a Bill of Lading When the Goods Have Not Been Received by the Carrier
The coming into force on January I, 1917 in the United States of the FXDMAL BILL Or LADING AcT1 has given new interest to a question which was at one time much debated, namely: should a carrier whose shipmaster or agent has signed a bill of lading be liable to an innocent holder for value of such bill of lading if the carrier can show that the goods were never shipped
Effects of Clinostat Rotation on Aurelia Statolith Synthesis
Aurelia ephyrae develop eight graviceptors (rhopalia) during their metamorphosis from polyps, which are used for positional orientation with respect to gravity. In three experiments for each speed of 1/15, 1/8, 1/2, 1, and 24 rpm, groups of six polyps were rotated in the horizontal or vertical plane (control) using clinostats. Other controls were kept stationary in the two planes. Ten ephyrae from each group were collected after 5 to 6 days at 27 C in iodine and the number of statoliths per rhopalium were counted. Statistical analyses of statolith numbers revealed that horizontal clinostat rotation at 1/4 and 1/2 rpm caused the formation of significantly fewer statoliths per rhopalium than were found in controls. The finding that these slow rates of rotation reduces statolith numbers suggests that the developing ephyrae were disoriented with respect to gravity at these speeds, causing fewer statocytes to differentiate or to mineralize
BlogForever D3.2: Interoperability Prospects
This report evaluates the interoperability prospects of the BlogForever platform. Therefore, existing interoperability models are reviewed, a Delphi study to identify crucial aspects for the interoperability of web archives and digital libraries is conducted, technical interoperability standards and protocols are reviewed regarding their relevance for BlogForever, a simple approach to consider interoperability in specific usage scenarios is proposed, and a tangible approach to develop a succession plan that would allow a reliable transfer of content from the current digital archive to other digital repositories is presented
Survival and Growth of American Alligator (Alligator mississippiensis) hatchlings after artificial incubation and repatriation
Hatchling American Alligators (Alligator mississippiensis) produced from artificially incubated
wild eggs were returned to their natal areas (repatriated). We compared artificially incubated and
repatriated hatchlings released within and outside the maternal alligator’s home range with naturally
incubated hatchlings captured and released within the maternal alligator’s home range on Lake Apopka,
Lake Griffin, and Orange Lake in Florida. We used probability of recapture and total length at approximately
nine months after hatching as indices of survival and growth rates. Artificially incubated hatchlings released
outside of the maternal alligator’s home range had lower recapture probabilities than either naturally
incubated hatchlings or artificially incubated hatchlings released near the original nest site. Recapture
probabilities of other treatments did not differ significantly. Artificially incubated hatchlings were
approximately 6% shorter than naturally incubated hatchlings at approximately nine months after hatching.
We concluded that repatriation of hatchlings probably would not have long-term effects on populations
because of the resiliency of alligator populations to alterations of early age-class survival and growth rates of
the magnitude that we observed. Repatriation of hatchlings may be an economical alternative to repatriation
of older juveniles for population restoration. However, the location of release may affect subsequent survival
and growth
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