Trends in source gases

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form

Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane)

Aggregates of cells, also known as multicellular aggregates (MCAs), have been used as microscale tissues in the fields of cancer biology, regenerative medicine, and developmental biology for many decades. However, small MCAs (fewer than 100 cells per aggregate) have remained challenging to manufacture in large quantities at high uniformity. Forced aggregation into microwells offers a promising solution for forming consistent aggregates, but commercial sources of microwells are expensive, complicated to manufacture, or lack the surface packing densities that would significantly improve MCA production. To address these concerns, we custom-modified a commercial laser cutter to provide complete control over laser ablation and directly generate microwells in a poly(dimethylsiloxane) (PDMS) substrate. We achieved ultra rapid microwell production speeds (>50000 microwells per h) at high areal packing densities (1800 microwells per cm2) and over large surface areas for cell culture (60 cm2). Variation of the PDMS substrate distance from the laser focal plane during ablation allowed for the generation of microwells with a variety of sizes, contours, and aspect ratios. Casting of high-fidelity microneedle masters in polyurethane allowed for non-ablative microwell reproduction through replica molding. MCAs of human bone marrow derived mesenchymal stem cells (hMSCs), murine 344SQ metastatic adenocarcinoma cells, and human C4-2 prostate cancer cells were generated in our system with high uniformity within 24 hours, and computer vision software aided in the ultra-high-throughput analysis of harvested aggregates. Moreover, MCAs maintained invasive capabilities in 3D migration assays. In particular, 344SQ MCAs demonstrated epithelial lumen formation on Matrigel, and underwent EMT and invasion in the presence of TGF-β. We expect this technique to find broad utility in the generation and cultivation of cancer cell aggregates, primary cell aggregates, and embryoid bodies

Final report for LDRD Project 94-ERD-037: multi-scale atmospheric simulation system

The purpose of this LDRD project was to develop a multi-scale atmospheric simulation system that could be applied to a diverse range of atmospheric problems, including key research issues related to global and regional climate change, studies of regional and local precipitation, and emergency predictions of the path and exposure concentration of toxic materials released into the atmosphere. In addition to its multi-scale nature, the new simulation system was to be designed such that the individual components of the system could be selected by users in an optimal way to support the research and operational needs of the entire Atmospheric Sciences Division

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin burn propagation into surrounding cold fuel, enabling the possibility of high energy gain. While scientific breakeven (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Wei Hua's Four Parameter Potential Comments and Computation of Moleculer Constants \alpha_e and \omega_e x_e

The value of adjustable parameter $C$ and the four-parameter potential $U(r) = D_{e}\left [ \frac{1-{exp}[-b(r-r_{e})]}{1-C{exp} [-b(r-r_{e})]} \right ]^{2}$ has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed, with $C$ derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei Hua. Average mean deviation has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from Levine2, Varshni and Morse potentials, respectively. Also Dunham's method has been used to express rotation-vibration interaction constant $(\alpha_{e})$ and anharmonocity constant $(\omega_{e}x_{e})$ in terms of $C$ and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For $\alpha_{e}$, the average mean deviation is 7.2% compared to 19.7% for Lippincott's potential which is known to be the best to predict the values. Average mean deviation for $(\omega_{e}x_{e})$ turns out to be 17.4% which is almost the same as found from Lippincott's potential function.Comment: 19 RevTex Pages, 1 Ps figure, submitted to J. Phys.

The H4K20 demethylase DPY-21 regulates the dynamics of condensin DC binding

Condensin is a multi-subunit SMC complex that binds to and compacts chromosomes. Unlike cohesin, in vivo regulators of condensin binding dynamics remain unclear. Here we addressed this question using C. elegans condensin DC, which specifically binds to and represses transcription of both X chromosomes in hermaphrodites for dosage compensation. Mutants of several chromatin modifiers that regulate H4K20me and H4K16ac cause varying degrees of X chromosome derepression. We used fluorescence recovery after photobleaching (FRAP) to analyze how these modifiers regulate condensin DC binding dynamics in vivo. We established FRAP using the SMC4 homolog DPY-27 and showed that a well-characterized ATPase mutation abolishes its binding. The greatest effect on condensin DC dynamics was in a null mutant of the H4K20me2 demethylase DPY-21, where the mobile fraction of the complex reduced from ∼30% to 10%. In contrast, a catalytic mutant of dpy-21 did not regulate condensin DC mobility. Separation of catalytic and non-catalytic activity is also supported by Hi-C data in the dpy-21 null mutant. Together, our results indicate that DPY-21 has a non-catalytic role in regulating the dynamics of condensin DC binding, which is important for transcription repression

Studies on the Restriction of Murine Leukemia Viruses by Mouse APOBEC3

APOBEC3 proteins function to restrict the replication of retroviruses. One mechanism of this restriction is deamination of cytidines to uridines in (−) strand DNA, resulting in hypermutation of guanosines to adenosines in viral (+) strands. However, Moloney murine leukemia virus (MoMLV) is partially resistant to restriction by mouse APOBEC3 (mA3) and virtually completely resistant to mA3-induced hypermutation. In contrast, the sequences of MLV genomes that are in mouse DNA suggest that they were susceptible to mA3-induced deamination when they infected the mouse germline. We tested the possibility that sensitivity to mA3 restriction and to deamination resides in the viral gag gene. We generated a chimeric MLV in which the gag gene was from an endogenous MLV in the mouse germline, while the remainder of the viral genome was from MoMLV. This chimera was fully infectious but its response to mA3 was indistinguishable from that of MoMLV. Thus, the Gag protein does not seem to control the sensitivity of MLVs to mA3. We also found that MLVs inactivated by mA3 do not synthesize viral DNA upon infection; thus mA3 restriction of MLV occurs before or at reverse transcription. In contrast, HIV-1 restricted by mA3 and MLVs restricted by human APOBEC3G do synthesize DNA; these DNAs exhibit APOBEC3-induced hypermutation