1,135 research outputs found
We Should Persuade Iran with Bargains not Bombs
Iranâs defiance of the IAEA has raised questions about Tehranâs desire to build nuclear weapons and this in turn has put that country squarely into the cross-hairs of the hawks in Washington. This case study reflects my search to answer a logical question stemming from the current backdrop; should we bomb Iran in order to prevent Tehran from obtaining nuclear weapons? I am a U.S. Marine Corps combat veteran from the first gulf war where I acted as an Iranian linguist signals intelligence and crypto-logic technician. It is impossible for me not to be passionate about our policies in the Middle East. My interpretation of this research tells me that the United States should begin direct communications with Iran. The social and behavioral sciences play a huge role in determining a policy outcome. Predicting how Iran and the rest of the world will react to our actions is of great importance. Just as a chess player tries to look at every future move, so to do we need a predictable strategy. This study will express the reasoning I have used to arrive at my claim that we should try to persuade Iran away from building nuclear weapons with bilateral talks and bargains not bombs. We, the United States, have not had a diplomatic relationship with Iran since the revolution in 1979. Twenty-seven years of not communicating. That is a long time to hold a grudge. In essence, I have discovered that now is the time to âburry the hatchetâ
Recommended from our members
Modulation of magnetic behavior via ligand-field effects in the trigonal clusters (PhL)Fe3L*3 (L* = thf, py, PMe2Ph)
Utilizing a hexadentate ligand platform, a series of trinuclear iron clusters (PhL)Fe3L*3 (PhLH6 1â4 MeC (CH2NPh-o-NPh)3; L* 1â4 tetrahydrofuran (1), pyridine (2), PMePh2 (3)) has been prepared. The phenyl substituents on the ligand sterically prohibit strong ironâiron bonding from occurring but maintain a sufficiently close proximity between iron centers to permit direct interactions. Coordination of the weak-field tetrahydrofuran ligand to the iron centers results in a well-isolated, high-spin S 1â4 6 or S 1â4 5 ground state, as ascertained through variable-temperature dc magnetic susceptibility and low- temperature magnetization measurements. Replacing the tetrahydrofuran ligands with stronger s-donating pyridine or tertiary phosphine ligands reduces the ground state to S 1â4 2 and gives rise to temperature-dependent magnetic susceptibility. In these cases, the magnetic susceptibility cannot be explained as arising simply from superexchange interactions between metal centers through the bridging amide ligands. Rather, the experimental data are best modelled by considering a thermally- induced variation in molecular spin state between S 1â4 2 and S 1â4 4. Fits to these data provide thermodynamic parameters of DH 1â4 406 cm 1 and Tc 1â4 187 K for 2 and DH 1â4 604 cm 1 and Tc 1â4 375 K for 3. The difference in these parameters is consistent with ligand field strength differences between pyridine and phosphine ligands. To rationalize the spin state variation across the series of clusters, we first propose a qualitative model of the Fe3 core electronic structure that considers direct FeâFe interactions, arising from direct orbital overlap. We then present a scenario, consistent with the observed magnetic behaviour, in which the s orbitals of the electronic structure are perturbed by substitution of the ancillary ligands.Chemistry and Chemical Biolog
Factors affecting local, regional, and global scale cyanobacterial dominance and secondary metabolite occurrence
Cyanobacteria are photosynthetic bacteria that serve as a primary producer in aquatic ecosystems. Cyanobacterial harmful algal blooms (CyanoHABs) are a major cause of water quality degradation in rivers, lakes, and estuaries worldwide because they disrupt food-webs and cause substantial changes in pH and dissolved oxygen. Additionally, many cyanobacterial species are capable of producing a suite of potent toxins and other secondary metabolites that cause taste and odor problems in drinking water supplies. The primary goal of my dissertation is to better understand the factors controlling CyanoHABs and their associated secondary metabolites at local, regional, and global scales. I examined the factors that control local-scale CyanoHABs and the cyanobacterial metabolites microcystin and geosmin by comparing 12 linear and non-linear regression modeling techniques using a continuous 14 year dataset collected from Cheney Reservoir, Kansas. In Chapter 2, I explored the factors that control regional-scale cyanobacterial abundance, microcystin, geosmin, and 2-methylisoborneol concentrations in 4 Midwestern US reservoirs. Then, I used a meta-analysis to evaluate the relation of persistent organic pollutants, which include herbicides, pesticides, pharmaceutical, personal care products, and industrial chemicals, to CyanoHABs on a global scale in Chapter 3. Overall, the three chapters indicate that cyanobacterial blooms and their associated metabolites are driven by numerous factors at different scales
Near-Infrared Spectroscopy Of The Nucleus Of Low-Activity Comet P/2016 BA During Its 2016 Close Approach
The Near-Earth Comet P/2016 BA (PanSTARRS) is a slow-rotatating
nearly-dormant object, a likely dynamical twin of 252P/LINEAR, and was recently
shown to have a mid-infrared spectrum very dissimilar to other comets.
BA also recently selected one of the back-up targets for the ESA's
\textit{Comet Interceptor}, so a clearer understanding of BA's modern
properties would not just improve our understanding of how comets go dormant,
but could also aid planning for a potential spacecraft visit. We present
observations of BA taken on two dates during its 2016 Earth close
approach with the NASA Infrared Telescope Facility, both of which are
consistent with direct observations of its nucleus. The reflectance spectrum of
BA is similar to 67P/Churyumov-Gerasimenko, albeit highly
phase-reddened. Thermal emission contaminates the reflectance spectrum at
longer wavelengths, which we correct with a new Markov Chain Monte Carlo
thermal modeling code. The models suggest 's visible geometric albedo
is , consistent with radar observations, its beaming parameter
is typical for NEOs observed in its geometry, and its reflectrance spectrum is
red and linear throughout H and K band. It appears very much like a "normal"
comet nucleus, despite its mid-infrared oddities. A slow loss of fine grains as
the object's activity diminished might help to reconcile some of the lines of
evidence, and we discuss other possibilities. A spacecraft flyby past BA
could get closer to the nucleus than with a more active target, and we
highlight some science questions that could be addressed with a visit to a
(nearly-)dormant comet.Comment: 18 pages, 3 figures, accepted for publication in the Planetary
Science Journal on April 1, 202
Recommended from our members
Expanded redox accessibility via ligand substitution in an octahedral Fe6Br6 cluster
Oxidation of the nominally all-ferrous hexanuclear cluster (HL)2Fe6 with six equivalents of ferrocenium in the presence of bromide ions results in a six-electron oxidation of the Fe6 core to afford the nominally all-ferric cluster (HL)2Fe6Br6. The hexabromide cluster is also structurally characterized in a 4+ core oxidation state. A structural comparison of these two clusters provides an insight into the Fe6 core electronic structure.Chemistry and Chemical Biolog
The Life and Times of a Buffalo Soldier, Sergeant Thomas Shaw, 9th United States Cavalry: Medal of Honor Recipient
This work describes the life and military career of Thomas Shaw, a former slave. Shaw served with the 9th United States Cavalry and was awarded the Medal of Honor.https://dspace.nku.edu/handle/11216/369
Cytotoxicity and estrogenicity of a novel 3-dimensional printed orthodontic aligner
INTRODUCTION
Orthodontic aligners printed with in-office 3-dimensional (3D) procedures have been described, but no data on their biocompatibility exist. This study investigates the cytotoxicity and estrogenicity of a 3D-printed orthodontic aligner by assessing its biological and behavioral effects.
METHODS
Ten sets of 1 type of aligner were immersed in sterile deionized water for 14 days, and the cytotoxicity and estrogenicity of released factors were assessed via MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays on human gingival fibroblasts and the estrogen-sensitive MCF-7 and the estrogen-insensitive MDA-MB-231 breast cancer cell lines. 17ÎČ-Estradiol and bisphenol-A were used as positive controls. The statistical analysis of data was performed with generalized linear models at a 0.05 level of significance.
RESULTS
No signs of cytotoxicity were seen for the aligner samples for concentrations (v/v) of 20% (P = 0.32), 10% (P = 0.79), or 5% (P = 0.76). The antioxidant activity expressed as the capacity to reduce intracellular levels of reactive oxygen species was not affected in the aligner samples (P = 0.08). No significant estrogenicity was induced by the aligner samples compared with eluents from the negative control for both MCF-7 (P = 0.65) and MDA-MB-231 (P = 0.78). As expected, 17ÎČ-Estradiol and bisphenol-A stimulated MCF-7 cell proliferation, whereas no effect was observed on MDA-MB-231 cells.
CONCLUSIONS
In conclusion, if any factors were released during the 14-day aging of 3D-printed aligners in water, these were not found to be cytotoxic for human gingival fibroblasts and did not affect their intracellular reactive oxygen species levels. Moreover, no estrogenic effects of these putative eluates were observed based on an E-screen assay
Physical Characterization of the December 2017 Outburst of the Centaur 174P/Echeclus
The Centaurs are the small solar system bodies intermediate between the
active inner solar system Jupiter Family Comets and their inactive progenitors
in the trans-Neptunian region. Among the fraction of Centaurs which show
comet-like activity, 174P/Echeclus is best known for its massive 2005 outburst
in which a large apparently active fragment was ejected above the escape
velocity from the primary nucleus. We present visible imaging and near-infrared
spectroscopy of Echeclus during the first week after its December 2017 outburst
taken at the Faulkes North & South Telescopes and the NASA IRTF, the largest
outburst since 2005. The coma was seen to be highly asymmetric. A secondary
peak was seen in the near-infrared 2D spectra, which is strongly hinted at in
the visible images, moving hyperbolically with respect to the nucleus. The
retrieved reflectance spectrum of Echelcus is consistent with the unobscured
nucleus but becomes bluer when a wider extraction aperture is used. We find
that Echeclus's coma is best explained as dominated by large blue dust grains,
which agrees with previous work. We also conducted a high-resolution orbital
integration of Echeclus's recent evolution and found no large orbital changes
that could drive its modern evolution. We interpret the second peak in the
visible and near-infrared datasets as a large cloud of larger-than-dust debris
ejected at the time of outburst. If Echeclus is typical of the Centaurs, there
may be several debris ejection or fragmentation events per year on other
Centaurs that are going unnoticed.Comment: Accepted for publication in the Astronomical Journal, 18 pages, 4
figures, 4 table
- âŠ