Thin Film Thermal Deposition at Various Pressures

This research was to verify the hypothesis that resistivity of metal\u27s thin film deposited in a low-pressure environment is the same as its solid material. Thermal Evaporation is a thin film deposition technique in which metal inside a vacuum is evaporated, then deposited onto a surface. Higher quality metal films are deposited when the vacuum pressure is lower. At higher pressures, more air molecules are trapped within the layers of metal, thus increasing scattering sites and increasing the resistance. However, reaching a lower pressure requires more time and effort. In this research, films were deposited at various pressures and resistivities were calculated for each film to determine an ideal pressure range that creates the least resistivity

Bioavailability of soil organic carbon and Fe as influenced by forestry practices in a subtropical coastal catchment

Potential impacts of plantation forestry practices on soil organic carbon and Fe available to microorganisms were investigated in a subtropical coastal catchment. The impacts of harvesting or replanting were largely limited to the soil top layer (0–10 cm depth). The thirty-year-old Pinus plantation showed low soil moisture content (Wc) and relatively high levels of soil total organic carbon (TOC). Harvesting and replanting increased soil Wc but reduced TOC levels. Mean dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased in harvested or replanted soils, but such changes were not statistically significant (P > 0.05). Total dithionite-citrate and aqua regia-extractable Fe did not respond to forestry practices, but acid ammonium oxalate and pyrophosphate-extractable, bioavailable Fe decreased markedly after harvesting or replanting. Numbers of heterotrophic bacteria were significantly correlated with DOC levels (P < 0.05), whereas Fe-reducing bacteria and S-bacteria detected using laboratory cultivation techniques did not show strong correlation with either soil DOC or Fe content

Family-friendly employment laws (re)assessed: the potential of care ethics

In light of various reforms in recent years, this article provides a (re)assessment of the broad package of family-friendly employment rights and relevant dispute resolution procedure now available to pregnant workers and working carers. It exposes how the realities of working life for many pregnant workers and carers and the long standing desire to promote gender equality in informal care-work remain at odds with the legal framework. An argument is presented in favour of an approach that, based upon the concept of care ethics, better engages with the impact of the provisions upon crucial interdependent care relationships

On Density-Critical Matroids

For a matroid $M$ having $m$ rank-one flats, the density $d(M)$ is $\tfrac{m}{r(M)}$ unless $m = 0$, in which case $d(M)= 0$. A matroid is density-critical if all of its proper minors of non-zero rank have lower density. By a 1965 theorem of Edmonds, a matroid that is minor-minimal among simple matroids that cannot be covered by $k$ independent sets is density-critical. It is straightforward to show that $U_{1,k+1}$ is the only minor-minimal loopless matroid with no covering by $k$ independent sets. We prove that there are exactly ten minor-minimal simple obstructions to a matroid being able to be covered by two independent sets. These ten matroids are precisely the density-critical matroids $M$ such that $d(M) > 2$ but $d(N) \le 2$ for all proper minors $N$ of $M$. All density-critical matroids of density less than $2$ are series-parallel networks. For $k \ge 2$, although finding all density-critical matroids of density at most $k$ does not seem straightforward, we do solve this problem for $k=\tfrac{9}{4}$.Comment: 16 page

The windows for kinetically mixed Z'-mediated dark matter and the galactic center gamma ray excess

One of the simplest hidden sectors with signatures in the visible sector is fermionic dark matter $\chi$ coupled to a $Z'$ gauge boson that has purely kinetic mixing with the standard model hypercharge. We consider the combined constraints from relic density, direct detection and collider experiments on such models in which the dark matter is either a Dirac or a Majorana fermion. We point out sensitivity to details of the UV completion for the Majorana model. For kinetic mixing parameter $\epsilon \le 0.01$, only relic density and direct detection are relevant, while for larger $\epsilon$, electroweak precision, LHC dilepton, and missing energy constraints become important. We identify regions of the parameter space of $m_\chi$, $m_{Z'}$, dark gauge coupling and $\epsilon$ that are most promising for discovery through these experimental probes. We study the compatibility of the models with the galactic center gamma ray excess, finding agreement at the 2-3$\sigma$ level for the Dirac model.Comment: 13 pages, 10 figures; v.2 added reference; v.3 minor clarifications, published versio

Multimediator models for the galactic center gamma ray excess

Tentative evidence for excess GeV-scale gamma rays from the galactic center has been corroborated by several groups, including the Fermi collaboration, on whose data the observation is based. Dark matter annihilation into standard model particles has been shown to give a good fit to the signal for a variety of final state particles, but generic models are inconsistent with constraints from direct detection. Models where the dark matter annihilates to mediators that subsequently decay are less constrained. We perform global fits of such models to recent data, allowing branching fractions to all possible fermionic final states to vary. The best fit models, including constraints from the AMS-02 experiment (and also antiproton ratio), require branching primarily to muons, with a $\sim 10-20\%$ admixture of $b$ quarks, and no other species. This suggests models in which there are two scalar mediators that mix with the Higgs, and have masses consistent with such a decay pattern. The scalar that decays to $\mu^+\mu^-$ must therefore be lighter than $2m_\tau \cong 3.6$ GeV. Such a small mass can cause Sommerfeld enhancement, which is useful to explain why the best-fit annihilation cross section is larger than the value needed for a thermal relic density. For light mediator masses $\sim (0.2-2)$ GeV, it can also naturally lead to elastic DM self-interactions at the right level for addressing discrepancies in small structure formation as predicted by collisionless cold dark matter.Comment: 18 pages, 14 figures; v2: updated CMB constraint and added references; v3 corrected direct detection cross sectio

Is Environmental Justice Good for White Folks?

This paper examines spatial variations in exposure to toxic air pollution from industrial facilities in urban areas of the United States, using geographic microdata from the U.S. Environmental Protection Agency’s Risk-Screening Environmental Indicators project. We find that average exposure in an urban area is positively correlated with the extent of racial and ethnic disparity in the distribution of the exposure burden. This correlation could arise from causal linkages in either or both directions: the ability to displace pollution onto minorities may lower the effective cost of pollution for industrial firms; and higher average pollution burdens may induce whites to invest more political capital in efforts to influence firms’ siting decisions. Furthermore, we find that in urban areas with higher minority pollution-exposure discrepancies, average exposures tend to be higher for all population subgroups, including whites. In other words, improvements in environmental justice in the United States could benefit not only minorities but also whites.environmental justice; air pollution; industrial toxics; Risk-Screening Environmental Indicators.

Regenerative failure and attribution

Purpose - The purpose of this paper is to focus on the processes that occur between entrepreneurs’ primary attribution for failure and the emergent learning dimensions from failure, in the context of regenerative failures. Design/methodology/approach - The study focusses on 21 entrepreneurs operating in the producing services sector, a major subsector of the Irish Information and Communication Technology industry. All the entrepreneurs experienced business failure and subsequently re-entered the entrepreneurial sphere at a later date. A qualitative approach examines their attributions for failure, responses to failure, and learning dimensions from failure. Findings - Regenerative entrepreneurs’ primary attributions for business failure are examined in detail; four types of failure attributions are uncovered – internal individual level; external firm level; external market level; and hybrid attributions. Entrepreneurs’ attributions impact their responses to the failure; this in turn affects entrepreneurial learning. When failure is primarily attributed to internal factors, the entrepreneur’s response is affective, leading to deep, personal learning about oneself. External attributions (both firm level and market level) result in a primarily behavioural response, with learning focussed on the venture, and networks and relationships. Those primarily attributing failure to hybrid factors have a largely cognitive response and they learn about venture management. Research limitations/implications - This study is a retrospective analysis of business failure. Originality/value - The study contributes to the growing literature on entrepreneurs’ attributions for business failure by focussing on regenerative failure; it links attributions to – responses to, and learning from, failure. The key contribution to knowledge emerges from the development of a model of the underlying processes affecting learning from failure for regenerative entrepreneurs. The research also establishes and identifies clear links between attributions, responses, and lessons learned in the context of regenerative failure