1,438 research outputs found

    A minichromosome of LGVI from crossing two quasi-terminal reciprocal translocations

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    Non-reciprocal translocations, in which one chromosome is a pure donor and another is a pure recipient, have found abundant uses in genetics, molecular biology, and cytology (Perkins 1997Advances in Genetics 36:239-398). Our original aim was to prepare a strain carrying a chromosome truncated in both arms, with the idea that such a small chromosome would be easily purified by pulsed field electrophoresis and would be a good preliminary substrate for genomic sequencing

    Full Aging in Spin Glasses

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    The discovery of memory effects in the magnetization decays of spin glasses in 1983 began a large effort to determine the exact nature of the decay. While qualitative arguments have suggested that the decay functions should scale as twt_{w}, the only time scale in the system, this type of scaling has not yet been observed. In this letter we report strong evidence for the scaling of the TRM magnetization decays as a function of twt_{w}. By varying the rate and the profile that the sample is cooled through its transition temperature to the measuring temperature, we find that the cooling plays a major role in determining scaling. As the effective cooling time decreases, ttw\frac {t}{t_{w}}scaling improves and for tceff<20st_{c}^{eff}<20s we find almost perfect ttw\frac{t}{t_{w}} scaling. We also find that subtraction of a stationary term from the magnetization decay has a small effect on the scaling but changes the form of the magnetization decay and improves overlap between curves produced with different twt_{w}.Comment: 4 pages, 3 figure

    Ultrafast demagnetization in the sp-d model: a theoretical study

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    We propose and analyze a theoretical model of ultrafast light-induced magnetization dynamics in systems of localized spins that are coupled to carriers' spins by sp-d exchange interaction. A prominent example of a class of materials falling into this category are ferromagnetic (III,Mn)V semiconductors, in which ultrafast demagnetization has been recently observed. In the proposed model light excitation heats up the population of carriers, taking it out of equilibrium with the localized spins. This triggers the process of energy and angular momentum exchange between the two spin systems, which lasts for the duration of the energy relaxation of the carriers. We derive the Master equation for the density matrix of a localized spin interacting with the hot carriers and couple it with a phenomenological treatment of the carrier dynamics. We develop a general theory within the sp-d model and we apply it to the ferromagnetic semiconductors, taking into account the valence band structure of these materials. We show that the fast spin relaxation of the carriers can sustain the flow of polarization between the localized and itinerant spins leading to significant demagnetization of the localized spin system, observed in (III,Mn)V materials.Comment: 15 pages, 8 figure

    Intense tumour-cell destruction by syngeneic mice: role of macrophages, complement activation and tumour-cell factors.

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    When injected i.p. and in large numbers (10(7)) into syngeneic mice, 125IUdR-labelled L1210 cells are rapidly destroyed in a small proportion of animals, while in the other animals the lysis is low. This bimodal distribution is clearly visible 24 h after cell injection. The intense lysis occurs in fewer animals when macrophage-derived lysosomal enzymes are inhibited by trypan blue and if the complement is depleted by high doses of cobra venom factor (CVF). The intense destruction occurs in more animals after adjuvant treatment, if the mice are latently contaminated, after a moderate production of C3b by low doses of CVF, or after the injection of a tumour-cell dialysate. The destruction seems to be the result of positive feedback reaction which involves at least macrophages and complement activation

    A miniprep procedure for isolating genomic DNA from Magnoporthe grisea

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    We have developed a simple miniprep procedure for the isolation of genomic DNA from the ascomycete Magnaporthe grisea. This pathogen of many grasses, including rice, has a moderate growth rate and produces intermediate to low numbers of conidia when grown in culture. Thus, in our previous DNA preparation procedure we inoculated swirling liquid cultures with mycelium that had been fragmented in a blender rather than with conidia. The mycelium obtained from these cultures was ground in liquid nitrogen for DNA extraction. Though the quantity and quality of DNA obtained by this method is satisfactory, the technique is too laborious for analysis of many strains. We developed the procedure described below to eliminate the need to fragment mycelium in a blender to inoculate cultures and to eliminate the need to grind mycelium in liquid nitrogen for DNA extraction. The new procedure, which relies on the enzymatic removal of cell walls and the lysis of protoplasts, should be readily adaptable to other filamentous fungi with growth characteristics similar to those of M. grisea

    Anharmonic Decay of Vibrational States in Amorphous Silicon

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    Anharmonic decay rates are calculated for a realistic atomic model of amorphous silicon. The results show that the vibrational states decay on picosecond timescales and follow the two-mode density of states, similar to crystalline silicon, but somewhat faster. Surprisingly little change occurs for localized states. These results disagree with a recent experiment.Comment: 10 pages, 4 Postscript figure

    ‘Blindness to the obvious’?: Treatment experiences and feminist approaches to eating disorders

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    Eating disorders (EDs) are now often approached as biopsychosocial problems, but the social or cultural aspects of the equation are often marginalised in treatment - relegated to mere contributory or facilitating factors. In contrast, feminist and socio-cultural approaches are primarily concerned with the relationship between EDs and the social/ cultural construction of gender. Yet although such approaches emerged directly from the work of feminist therapists, the feminist scholarship has increasingly observed, critiqued and challenged the biomedical model from a scholarly distance. As such, this article draws upon data from 15 semi-structured interviews with women in the UK context who have experience of anorexia and/or bulimia in order to explore a series of interlocking themes concerning the relationship between gender identity and treatment. In engaging the women in debate about the feminist approaches (something which has been absent from previous feminist work), the article explores how gender featured in their own understandings of their problem, and the ways in which it was - or rather wasn’t - addressed in treatment. The article also explores the women’s evaluations of the feminist discourse, and their discussions of how it might be implemented within therapeutic and clinical contexts
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