On the Disalignment of Interstellar Grains

Several mechanisms have been proposed to explain the alignment of grains with the interstellar magnetic field, including paramagnetic dissipation, radiative torques, and supersonic gas-grain streaming. These must compete with disaligning processes, including randomly directed torques arising from collisions with gas atoms. I describe a novel disalignment mechanism for grains that have a time-varying electric dipole moment and that drift across the magnetic field. Depending on the drift speed, this mechanism may yield a much shorter disalignment timescale than that associated with random gas atom impacts. For suprathermally rotating grains, the new disaligning process may be more potent for carbonaceous dust than for silicate dust. This could result in efficient alignment for silicate grains but poor alignment for carbonaceous grains.Comment: 19 pages, 3 figures, submitted to Ap

A series of six compact fungal transformation vectors containing polylinkers with multiple unique restriction sites

In comparison with transformation vectors available for use in E. coli or yeast, there has been relatively little development of vectors for use in filamentous fungi. For example, expression yeast vectors carrying polylinkers flanked by promoters and terminators are available for various uses but such vectors have not been in the public domain for researchers working with filamentous fungi

A lambda/plasmid Cre/lox hybrid vector for large genomic (18kb) fragment insertions and fungal genomic library construction

We have previously constructed lambda/plasmid hybrid vectors designed for both fungal cDNA and genomic library construction (Brunelli and Pall, 1994 Fungal Genet. Newslet. 41:63-65). The genomic library inserts, however, were limited to about 11 kb in size due to the size limitations of lambda packaging. We have constructed a similar vector that has three advantages over these earlier hybrid vectors, as discussed further below. The plasmid pBARGEM7-2 (Pall and Brunelli, 1993. Fungal Genet. Newslet. 40:59-61) was modified by inserting a stuffer sequence into the BamHI site of the polylinker. The stuffer sequence was about 6 kb and can be cut out with BamHI, yielding two BamHI fragments of about 4.5 kb and 1.5 kb. The 4.5 kb fragment contains the lacZ gene, producing very blue colonies (or plaques in lambda) on Xgal medium

New plasmid and lambda/plasmid hybrid vectors and a Neurospora crassa genomic library containing the bar selectable marker and the Cre/lox site-specific recombination system for use in filamentous fungi

In the previous Fungal Genetics Newsletter, we described a series of plasmid vectors constructed carrying the bar gene as a selectable marker for use in filamentous fungi (Pall and Brunelli 1993 Fungal Genetics Newsl. 40:59-63; Pall 1993 Fungal Genetics Newsl. 40:58). In this note, we describe an additional plasmid expression vector carrying this selectable marker and the construction of four llambda/plasmid hybrid vectors carrying the bar gene within plasmid inserts that can excise by Cre/lox-mediated excision. A Neurospora crassa genomic library constructed in one of these lambda/plasmid hybrid vectors is also described below

Metformin induces distinct bioenergetic and metabolic profiles in sensitive versus resistant high grade serous ovarian cancer and normal fallopian tube secretory epithelial cells.

Metformin is a widely used agent for the treatment of diabetes and infertility, however, it has been found to have anti-cancer effects in a variety of malignancies including high grade serous ovarian cancer (HGSC). Studies describing the mechanisms by which metformin affects HGSC are ongoing, but detailed analysis of its effect on the cellular metabolism of both HGSC cells and their precursor, normal fallopian tube secretory epithelial cells (FTSECs), is lacking. We addressed the effects of metformin and the more potent biguanide, phenformin, on HGSC cell lines and normal immortalized FTSECs. Cell proliferation assays identified that FTSECs and a subset of HGSC cell lines are relatively resistant to the anti-proliferative effects of metformin. Bioenergetic and metabolomic analyses were used to metabolically differentiate the metformin-sensitive and metformin-resistant cell lines. Bioenergetically, biguanides elicited a significant decrease in mitochondrial respiration in all HGSC cells and FTSECs. However, biguanides had a greater effect on mitochondrial respiration in metformin sensitive cells. Metabolomic analysis revealed that metformin and phenformin generally induce similar changes in metabolic profiles. Biguanide treatment led to a significant increase in NADH in FTSECs and HGSC cells. Interestingly, biguanide treatment induced changes in the levels of mitochondrial shuttle metabolites, glycerol-3-phopshate (G3P) and aspartate, specifically in HGSC cell lines and not in FTSECs. Greater alterations in G3P or aspartate levels were also found in metformin sensitive cells relative to metformin resistant cells. These data identify bioenergetic and HGSC-specific metabolic effects that correlate with metformin sensitivity and novel metabolic avenues for possible therapeutic intervention

The Size and Origin of Metal-enriched Regions in the Intergalactic Medium from Spectra of Binary Quasars

We present tomography of the circum-galactic metal distribution at redshift 1.7-4.5 derived from echellete spectroscopy of binary quasars. We find C IV systems at similar redshifts in paired sightlines more often than expected for sightline-independent redshifts. As the separation of the sightlines increases from 36 kpc to 907 kpc, the amplitude of this clustering decreases. At the largest separations, the C IV systems cluster similar to the Lyman-break galaxies studied by Adelberger et al. in 2005. The C IV systems are significantly less correlated than these galaxies, however, at separations less than R_1 0.42 ± 0.15 h^( –1) comoving Mpc. Measured in real space, i.e., transverse to the sightlines, this length scale is significantly smaller than the break scale estimated previously from the line-of-sight correlation function in redshift space by Scannapieco et al. in 2006. Using a simple model, we interpret the new real-space measurement as an indication of the typical physical size of enriched regions. We adopt this size for enriched regions and fit the redshift-space distortion in the line-of-sight correlation function. The fitted velocity kick is consistent with the peculiar velocity of galaxies as determined by the underlying mass distribution and places an upper limit on the average outflow (or inflow) speed of metals. The implied timescale for dispersing metals is larger than the typical stellar ages of Lyman-break galaxies, and we argue that enrichment by galaxies at z > 4.3 played a greater role in dispersing metals. To further constrain the growth of enriched regions, we discuss empirical constraints on the evolution of the C IV correlation function with cosmic time. This study demonstrates the potential of tomography for measuring the metal enrichment history of the circum-galactic medium

AvatarSAT: An Auto-tuning Boolean SAT Solver

We present AvatarSAT, a SAT solver that uses machine-learning classifiers to automatically tune the heuristics of an off-the-shelf SAT solver on a per-instance basis. The classifiers use features of both the input and conflict clauses to select parameter settings for the solver's tunable heuristics. On a randomly selected set of SAT problems chosen from the 2007 and 2008 SAT competitions, AvatarSAT is, on average, over two times faster than MiniSAT based on the geometric mean speedup measure and 50% faster based on the arithmeticmean speedup measure. Moreover, AvatarSAT is hundreds to thousands of times faster than MiniSAT on many hard SAT instances and is never more than twenty times slower than MiniSAT on any SAT instance