The relationship between fragility, configurational entropy and the potential energy landscape of glass forming liquids

Glass is a microscopically disordered, solid form of matter that results when a fluid is cooled or compressed in such a fashion that it does not crystallise. Almost all types of materials are capable of glass formation -- polymers, metal alloys, and molten salts, to name a few. Given such diversity, organising principles which systematise data concerning glass formation are invaluable. One such principle is the classification of glass formers according to their fragility\cite{fragility}. Fragility measures the rapidity with which a liquid's properties such as viscosity change as the glassy state is approached. Although the relationship between features of the energy landscape of a glass former, its configurational entropy and fragility have been analysed previously (e. g.,\cite{speedyfr}), an understanding of the origins of fragility in these features is far from being well established. Results for a model liquid, whose fragility depends on its bulk density, are presented in this letter. Analysis of the relationship between fragility and quantitative measures of the energy landscape (the complicated dependence of energy on configuration) reveal that the fragility depends on changes in the vibrational properties of individual energy basins, in addition to the total number of such basins present, and their spread in energy. A thermodynamic expression for fragility is derived, which is in quantitative agreement with {\it kinetic} fragilities obtained from the liquid's diffusivity.Comment: 8 pages, 3 figure

Cholesterol catalyses Aβ42 aggregation through a heterogeneous nucleation pathway in the presence of lipid membranes.

Alzheimer's disease is a neurodegenerative disorder associated with the aberrant aggregation of the amyloid-β peptide. Although increasing evidence implicates cholesterol in the pathogenesis of Alzheimer's disease, the detailed mechanistic link between this lipid molecule and the disease process remains to be fully established. To address this problem, we adopt a kinetics-based strategy that reveals a specific catalytic role of cholesterol in the aggregation of Aβ42 (the 42-residue form of the amyloid-β peptide). More specifically, we demonstrate that lipid membranes containing cholesterol promote Aβ42 aggregation by enhancing its primary nucleation rate by up to 20-fold through a heterogeneous nucleation pathway. We further show that this process occurs as a result of cooperativity in the interaction of multiple cholesterol molecules with Aβ42. These results identify a specific microscopic pathway by which cholesterol dramatically enhances the onset of Aβ42 aggregation, thereby helping rationalize the link between Alzheimer's disease and the impairment of cholesterol homeostasis

Review of Coronal Oscillations - An Observer's View

Recent observations show a variety of oscillation modes in the corona. Early non-imaging observations in radio wavelengths showed a number of fast-period oscillations in the order of seconds, which have been interpreted as fast sausage mode oscillations. TRACE observations from 1998 have for the first time revealed the lateral displacements of fast kink mode oscillations, with periods of ~3-5 minutes, apparently triggered by nearby flares and destabilizing filaments. Recently, SUMER discovered with Doppler shift measurements loop oscillations with longer periods (10-30 minutes) and relatively short damping times in hot (7 MK) loops, which seem to correspond to longitudinal slow magnetoacoustic waves. In addition, propagating longitudinal waves have also been detected with EIT and TRACE in the lowest density scale height of loops near sunspots. All these new observations seem to confirm the theoretically predicted oscillation modes and can now be used as a powerful tool for ``coronal seismology'' diagnostic.Comment: 5 Figure

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Not AvailableIN THIS PAPER,THE AUTHORS DISCUSS THE PROBLEM OF MASS EROSION THROUGH LANDSLIDES , MINESPOILS AND STREAM BANK. THE FACTORS RESPONSIBLE FOR SUCH PROBLEMS ARE ALSO ENUMERATED. RECLAMATION TECHNIQUES INCLUDING ENGINEERING MEASURES FOR SLOPE STABILIZATION AND GRADE STABILIZATION ; MEASURES FOR TORRENT TRAINING AND RESTORATION OF DEGRADED SITES ARE DESCRIBED IN GREATER DETAILS. THE RESEARCH FINDINGS IN RESPECT OF ECO- RESTORATION OF MINED AREAS AT SAHASTRADHARA AND LANDSLIDE CONTROL PROJECT AT NALOTA NALA IN MUSSOORIE HILLS HAVE BEEN PRESENTED.Not Availabl

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Not AvailableTHE PAPER DEALS WITH RAIN WATER HARVESTING AND COLLECTION OF RUNOFF INTO THE FARM PONDS FOR SUBSEQUENT USE FOR CROP PRODUCTION , FISH PRODUCTION, LIVESTOCK DRINKING PURPOSE AND FLOOD CONTROL. KINDS OF PONDS, SIZES AND CAPABILITIES OF PONDS AND CONTROLLING THE SEEPAGE LOSSES IN THE PONDS HAVE ALSO BEEN DESCRIBED.Not Availabl

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Not AvailableLANDSLIDES , MINESPOILS AND TORRENTS ARE THE MAJOR ENVIRONMENTAL PROBLEMS IN HIMALAYAS IN GENERAL AND DOON VALLEY IN PARTICULAR , RESULTING IN SEVERE SOIL EROSION , LAND DEGRADATION AND OTHER ASSOCIATED PROBLEMS. CSWCRTI , DEHRADUN UNDERTOOK PILOT PROJECTS AFFECTED BY THESE PROBLEMS AT THREE TYPICAL SITES IN THE DOON VALLEY AND EVOLVED PACKAGE OF BIO- ENGINEERING MEASURES ON WATERSHED BASIS FOR THEIR REHABILITATION. THESE MEASURES ARE DESCRIBED IN THIS PAPER. THE MONITORING OF THE TREATED WATERSHEDS SHOWS ECO- REJUVENATION WITHIN A PERIOD OF 5-6 YEARS WITH IMPROVEMENT IN THE HYDROLOGIC REGIME.Not Availabl

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Not AvailableIN THE RECENT PAST, THERE HAS BEEN A RAPID INCREASE IN DEVELOPMENTAL ACTIVITIES LEADING TO LAND DEGRADATION IN THE FORM OF LANDSLIDES , MINE SPOILS AND DRY AND BOUNDARY TORRENTS. THESE DEGRADATION PROBLEMS CAN BE SOLVED BY ADOPTING PROTECTIVE , STUDYING ENGINEERING AND VEGETATIVE MEASURES. THE RESULTS OF AN EXPERIMENTAL STUDY HAVE BEEN DISCUSSED WHICH INDICATED REDUCTION IN RUNOFF AND SOIL LOSS AND INCREASED REGULATED FLOW OF WATER EVEN IN DRY WEATHER.Not Availabl

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Not AvailableIN THIS PAPER THE AUTHORS HAVE ATTEMPTED TO CRITICALLY REVIEW THE STUDIES CARRIED OUT ON THE PERFORMANCE OF VARIOUS TYPES AND SHAPES OF SPURS WHICH ARE MADE TO PROTECT THE STREAM BANKS FROM EROSION AND FOR TRAINING OF STREAM FLOW. THE AUTHORS SUGGEST THAT LABORATORY STUDIES IN THE HYDRAULIC FLUME MAKE IT FEASIBLE TO STUDY THE PERFORMANCE OF SPURS IN TERMS OF THEIR STABILITY, SCOUR PATTERN AND SEDIMENT MOVEMENT UNDER CONTROLLED CONDITIONS OF FLOW, BED SLOPE AND BED MATERIAL SIZE. MATHEMATICAL MODELS CAN BE DEVELOPED FROM SUCH INFORMATION. THE LENGTH OF THE SPUR SHOULD BE SUCH THAT IT INTERFERES LEAST WITH THE RIVER REGIME AND A LARGE VALUE OF OPENING RATIO ( GREATER THAN 0.7) IS OBTAINED. AMONG THE FEW STUDIES CONDUCTED ON PERMEABLE SPURS, IT WAS OBSERVED THAT THEY PROTECT STREAM BANK FOR LONGER LENGTH AND CAUSE SMALLER MAGNITUDE OF THE MAXIMUM DEPTH OF SCOUR THAN THE SOLID SPUR.Not Availabl

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Not AvailableTHE PAPER ATTEMPTS TO DEVELOP A FINITE ELEMENT MODEL FOR SIMULATING RUNOFF AND SOIL EROSION ON MECHANICALLY TREATED AGRICULTURAL LANDS , VALIDATE THE MODEL UNDER FIELD CONDITIONS AND EVALUATE THE EFFECT OF SOIL, TOPOGRAPHIC, CLIMATIC AND LANDUSE PARAMETERS ON RUNOFF AND SEDIMENT YIELDS. THE MODEL HAS BEEN VALIDATED WITH FIELD DATA. THE SENSITIVITY ANALYSIS FOR CONSERVATION BENCH TERRACE SYSTEM HAS BEEN CARRIED OUT. APPLICATION OF THE MODEL AS A PLANNING TOOL FOR SOIL CONSERVATION AND IMPACT OF LAND USE CHANGES ON RUNOFF AND SOIL EROSION ON WATERSHEDS BASIS HAVE ALSO BEEN DISCUSSED.Not Availabl