Targeted gene disruption of the endogenous c-abl locus by homologous recombination with DNA encoding a selectable fusion protein

We have introduced a substitution mutation into the c-abl locus of murine embryonic stem cells by homologous recombination between exogenously added DNA and the endogenous gene. Model constructs were initially generated that consisted of a promoterless selectable neomycin resistance marker inserted into the v-abl gene of the complete Abelson murine leukemia virus genome, designed to be expressed either as a fusion protein or by translational restart. Tests of these viral genomes for transmission of v-abl and neo markers showed more stable coexpression in a protein fusion construct. The neo fusion was subcloned from this v-abl construct into a promoterless c-abl fragment, and the resulting DNA was used to transform embryonic stem cells. Direct screening of genomic DNAs showed that a high proportion of drug-resistant clones arose from homologous recombination into the endogenous c-abl locus

Subseasonal-to-interdecadal variability of the Australian monsoon over North Queensland

Daily rainfall occurrence and amount at 11 stations over North Queensland are examined for summers 1958–1998, using a Hidden Markov Model (HMM). Daily rainfall variability is described in terms of the occurrence of five discrete ‘weather states’, identified by the HMM. Three states are characterized respectively by very wet, moderately wet, and dry conditions at most stations; two states have enhanced rainfall along the coast and dry conditions inland. Each HMM rainfall state is associated with a distinct atmospheric circulation regime. The two wet states are accompanied by monsoonal circulation patterns with large-scale ascent, low-level inflow from the north-west, and a phase reversal with height; the dry state is characterized by circulation anomalies of the opposite sense. Two of the states show significant associations with midlatitude synoptic waves. Variability of the monsoon on time-scales from subseasonal to interdecadal is interpreted in terms of changes in the frequency of occurrence of the five HMM rainfall states. Large subseasonal variability is identified in terms of active and break phases, and a highly variable monsoon onset date. The occurrence of the very wet and dry states is somewhat modulated by the Madden–Julian oscillation. On interannual time-scales, there are clear relationships with the El Niño–Southern Oscillation and Indian Ocean sea surface temperatures (SSTs). Interdecadal monsoonal variability is characterized by stronger monsoons during the 1970s, and weaker monsoons plus an increased prevalence of drier states in the later part of the record. Stochastic simulations of daily rainfall occurrence and amount at the 11 stations are generated by introducing predictors based on large-scale precipitation from (a) reanalysis data, (b) an atmospheric general circulation model (GCM) run with observed SST forcing and (c) antecedent June–August Pacific SST anomalies. The reanalysis large-scale precipitation yields relatively accurate station-level simulations of the interannual variability of daily rainfall amount and occurrence, with rainfall intensity less well simulated. At some stations, interannual variations in 10-day dry-spell frequency are also simulated reasonably well. The interannual quality of the simulations is markedly degraded when the GCM simulations are used as inputs, while antecedent Pacific SST inputs yield an anomaly correlation skill comparable to that of the GCM

Embryonic Lethality in Mice Homozygous for a Targeted Disruption of the N-myc Gene

The N-myc gene encodes a putative transcription factor that is thought to function in the regulation of gene expression during cell differentiation and/or growth. To examine the role of N-myc during development, we have used targeted mutagenesis in embryonic stem cells to produce a mouse line that carries an N-myc null allele. Mice homozygous for the mutation died between 10.5 and 12.5 days of gestation. Histological analysis of mutant embryos revealed that organs and tissues expected at these stages of development were present. However, multiple defects were observed, primarily in tissues and organs that normally express N-myc. In particular, mutant hearts were underdeveloped, often retaining the S-shape more typical of 9-day-old embryos. In addition, cranial and spinal ganglia were reduced in size and/or cellularity. Most of the noted defects were more consistent with a role of N-myc in proliferation of precursor populations than with a block in differentiation per se, at least at these early stages. These results demonstrate that N-myc plays an essential role during development and clearly confirm that N-myc has a physiological function that is distinct from that of the other myc-family genes

Lattice-stiffening transition in copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%)

We report the discovery of a compressibility phase transition at 160 K in crystalline copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%). This phase transition is distinct from the known bulk ferroelectric-paraelectric phase transition at 353 K and surface ferroelectric phase transition at 295 K. The new phase transition is characterized by an increase in the effective Debye temperature from 48 to 245 K along the 〈010〉 direction as the temperature falls below 160 K. This phase transition is evident in neutron scattering, x-ray diffraction, angle-resolved photoemission, and in the dipole active phonon modes in electron energy-loss spectroscopy. © 1999 The American Physical Society

TSIL: a program for the calculation of two-loop self-energy integrals

TSIL is a library of utilities for the numerical calculation of dimensionally regularized two-loop self-energy integrals. A convenient basis for these functions is given by the integrals obtained at the end of O.V. Tarasov's recurrence relation algorithm. The program computes the values of all of these basis functions, for arbitrary input masses and external momentum. When analytical expressions in terms of polylogarithms are available, they are used. Otherwise, the evaluation proceeds by a Runge-Kutta integration of the coupled first-order differential equations for the basis integrals, using the external momentum invariant as the independent variable. The starting point of the integration is provided by known analytic expressions at (or near) zero external momentum. The code is written in C, and may be linked from C, C++, or Fortran. A Fortran interface is provided. We describe the structure and usage of the program, and provide a simple example application. We also compute two new cases analytically, and compare all of our notations and conventions for the two-loop self-energy integrals to those used by several other groups.Comment: 31 pages. Updated to reflect new functionality through v1.4 May 2016 and new information about use with C++. Source code and documentation are available at http://www.niu.edu/spmartin/TSIL or http://faculty.otterbein.edu/DRobertson/tsil