226 research outputs found
Strained alkynes derived from 2,2′-dihydroxy-1,1′-biaryls ; synthesis and copper-free cycloaddition with azides
A series of strained alkynes were prepared from 2,2′-dihydroxy-biaryls. Several were characterised by X-ray crystallography, revealing strained C(sp)–C(sp)–C(sp3) bond angles in the range of 163–167°. Their cycloadditions with azides proceed without a catalyst. Functionalised versions of these reagents have potential applications to materials synthesis and bioconjugations
Nuclear expansion and symmetry energy of hot nuclei
The decrease in the symmetry energy of hot nuclei populated in Ni +
Ni, Fe + Ni and Fe + Fe reactions at beam
energies of 30, 40, and 47 MeV/nucleon, as a function of excitation energy is
studied. It is observed that this decrease is mainly a consequence of
increasing expansion or decreasing density rather than the increasing
temperature. The results are in good agreement with the recently reported
microscopic calculation based on the Thomas-Fermi approach. An empirical
relation to study the symmetry energy of finite nuclei in various mass region
is proposed.Comment: 10 pages, 2 figure
Analysis of fragment yield ratios in the nuclear phase transition
The critical phenomena of the liquid-gas phase transition has been
investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon
using the Landau free energy approach with isospin asymmetry as an order
parameter. Fits to the free energy of fragments showed three minima suggesting
the system to be in the regime of a first order phase transition. The relation
m =-{\partial}F/{\partial}H, which defines the order parameter and its
conjugate field H, has been experimentally verified from the linear dependence
of the mirror nuclei yield ratio data, on the isospin asymmetry of the source.
The slope parameter, which is a measure of the distance from a critical
temperature, showed a systematic decrease with increasing excitation energy of
the source. Within the framework of the Landau free energy approach, isoscaling
provided similar results as obtained from the analysis of mirror nuclei yield
ratio data. We show that the external field is primarily related to the minimum
of the free energy, which implies a modification of the source concentration
\Delta used in isospin studies
Analysis of fragment yield ratios in the nuclear phase transition
The critical phenomena of the liquid-gas phase transition has been
investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon
using the Landau free energy approach with isospin asymmetry as an order
parameter. Fits to the free energy of fragments showed three minima suggesting
the system to be in the regime of a first order phase transition. The relation
m =-{\partial}F/{\partial}H, which defines the order parameter and its
conjugate field H, has been experimentally verified from the linear dependence
of the mirror nuclei yield ratio data, on the isospin asymmetry of the source.
The slope parameter, which is a measure of the distance from a critical
temperature, showed a systematic decrease with increasing excitation energy of
the source. Within the framework of the Landau free energy approach, isoscaling
provided similar results as obtained from the analysis of mirror nuclei yield
ratio data. We show that the external field is primarily related to the minimum
of the free energy, which implies a modification of the source concentration
\Delta used in isospin studies
Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy
Background
A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets.
Methods
Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis.
Results
A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001).
Conclusion
We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty
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