On the Role of Metastable States in Low Pressure Oxygen Discharges

We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code {\tt oopd1} to explore the spatio-temporal evolution of the electron heating mechanism in a capacitively coupled oxygen discharge in the pressure range 10 -- 200 mTorr. The electron heating is most significant in the sheath vicinity during the sheath expansion phase. We explore how including and excluding detachment by the singlet metastable states O$_2$(a$^1 \Delta_{\rm g}$) and O$_2$(b$^1\Sigma_{\rm g}^+$) influences the heating mechanism, the effective electron temperature and electronegativity, in the oxygen discharge. We demonstrate that the detachment processes have a significant influence on the discharge properties, in particular for the higher pressures. At 10 mTorr the time averaged electron heating shows mainly ohmic heating in the plasma bulk (the electronegative core) and at higher pressures there is no ohmic heating in the plasma bulk, that is electron heating in the sheath regions dominates.Comment: submitted to AIP Conference Proceeding

Immunosterilisation affecting the functional level of reproductive hormones.

Immunosterilisation in males is aimed at inhibiting the production of sperm by eliciting antibodies capable of neutralising the hormones that control spermatogenesis, gonadotrophin-releasing hormone (GnRH), luteinising hormone (LH), follicle- stimulating hormone (FSH) and testosterone. This approach is attractive as an alternative to surgical procedures for companion animals and animals bred for food purposes. Traditional castration can be time consuming and have a risk of infection and mortality. Additionally, immunosterilisation can improve meat and carcass characteristics in cattle, sheep, goats and boars, improve feed efficiency relative to castrates and reduce male aggressive behaviour and male-associated odours. Although immunosterilisation is unlikely to be used for fertility control in humans, there is great interest in using active immunisation against GnRH as means of treating steroid- dependent pathologies such as prostate cancer. The work described in this thesis explores a number of design strategies aimed at producing an improved GnRH-based vaccine for male animals that would cause effective and irreversible sterilisation. Preliminary studies investigating the feasibility of increasing the efficacy of a GnRH vaccine by additionally neutralising another component in the hormonal reproductive pathway, LH, are also presented. GnRH or a GnRH-analogue (GnRH-D6-Lys) were chemically coupled to the carrier molecules tetanus toxoid (TT) and heat shock protein 70 (Hsp70). Alternatively, they were expressed on the surface of bacteriophage particles or synthesised as part of a multiple antigen peptide (MAP) system along with a T helper cell epitope. These different carrier-antigen complexes in either Ribi adjuvant or without active adjuvant (in Freund's incomplete adjuvant) were used to immunise groups of male Balb/c mice repeatedly from 3 weeks of age to 12 weeks of age. Hormone-specific antibodies and serum testosterone levels were measured. In addition, the testes and the accessory reproductive organs were analysed for histological and morphological changes. The level of the testosterone-dependent relaxin-like factor (RLE) mRNA in the testes was also determined. All the groups immunised with GnRH or ovine LH (oLH) conjugates mounted a hormone-specific antibody response, albeit at levels which varied between groups and between individual animals. Animals immunised with GnRH coupled to Hsp70 produced the highest level of specific antibodies. Although serum testosterone levels also varied, signs of testosterone reduction were apparent in histological analysis of the testes, involution of the seminiferous vesicles and prostate gland, and in the RLF expression in the testes following immunisations with most GnRH conjugates. We hypothesised that targeting more than one component of the hormonal pathway (e.g. GnRH and LH) would achieve a more effective immunosterilisation than seen in experiments following immunisation with either one of the hormones alone. We did not, however, see such an additive effect in animals immunised with both GnRH constructs and oLH. Although the animals mounted an appreciable GnRH response, they produced very little oLH-specific IgG compared to mice immunised with oLH alone. These observations are discussed in relation to antigenic competition, carrier determinants and adjuvanticity

On singlet metastable states, ion flux and ion energy in single and dual frequency capacitively coupled oxygen discharges

We apply particle-in-cell simulations with Monte Carlo collisions to study the influence of the singlet metastable states on the ion energy distribution in single and dual frequency capacitively coupled oxygen discharges. For this purpose, the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used, in which the discharge model includes the following nine species: electrons, the neutrals O(3P) and O2(X3 σ-g), the negative ions O-, the positive ions O+ and O, and the metastables O(1D), O2(a1 Δg)and O2(b1 σ+g). Earlier, we have explored the effects of adding the species O2(a1 Δg) and O2(b1 σ+g), and an energy-dependent secondary electron emission yield for oxygen ions and neutrals, to the discharge model. We found that including the two molecular singlet metastable states decreases the ohmic heating and the effective electron temperature in the bulk region (the electronegative core). Here we explore how these metastable states influence dual frequency discharges consisting of a fundamental frequency and the lowest even harmonics. Including or excluding the detachment reactions of the metastables O2(a1 Δg) and O2(b1 σ +g) can shift the peak electron temperature from the grounded to the powered electrode or vice versa, depending on the phase difference of the two applied frequencies. These metastable states can furthermore significantly influence the peak of the ion energy distribution for O-ions bombarding the powered electrode, and hence the average ion energy upon bombardment of the electrode, and lower the ion flux

A Finite SS-Matrix

When massless particles are involved, the traditional scattering matrix ($S$-matrix) does not exist: it has no rigorous non-perturbative definition and has infrared divergences in its perturbative expansion. The problem can be traced to the impossibility of isolating single-particle states at asymptotic times. On the other hand, the troublesome non-separable interactions are often universal: in gauge theories they factorize so that the asymptotic evolution is independent of the hard scattering. Exploiting this factorization property, we show how a finite "hard" $S$-matrix, $S_H$, can be defined by replacing the free Hamiltonian with a soft-collinear asymptotic Hamiltonian. The elements of $S_H$ are gauge invariant and infrared finite, and exist even in conformal field theories. One can interpret elements of $S_H$ alternatively 1) as elements of the traditional $S$-matrix between dressed states, 2) as Wilson coefficients, or 3) as remainder functions. These multiple interpretations provide different insights into the rich structure of $S_H$.Comment: 5 pages, 5 figure

Proteomic profile of KSR1-regulated signalling in response to genotoxic agents in breast cancer

Kinase suppressor of Ras 1 (KSR1) has been implicated in tumorigenesis in multiple cancers, including skin, pancreatic and lung carcinomas. However, our recent study revealed a role of KSR1 as a tumour suppressor in breast cancer, the expression of which is potentially correlated with chemotherapy response. Here, we aimed to further elucidate the KSR1-regulated signalling in response to genotoxic agents in breast cancer. Stable isotope labelling by amino acids in cell culture (SILAC) coupled to high-resolution mass spectrometry (MS) was implemented to globally characterise cellular protein levels induced by KSR1 in the presence of doxorubicin or etoposide. The acquired proteomic signature was compared and GO-STRING analysis was subsequently performed to illustrate the activated functional signalling networks. Furthermore, the clinical associations of KSR1 with identified targets and their relevance in chemotherapy response were examined in breast cancer patients. We reveal a comprehensive repertoire of thousands of proteins identified in each dataset and compare the unique proteomic profiles as well as functional connections modulated by KSR1 after doxorubicin (Doxo-KSR1) or etoposide (Etop-KSR1) stimulus. From the up-regulated top hits, several proteins, including STAT1, ISG15 and TAP1 are also found to be positively associated with KSR1 expression in patient samples. Moreover, high KSR1 expression, as well as high abundance of these proteins, is correlated with better survival in breast cancer patients who underwent chemotherapy. In aggregate, our data exemplify a broad functional network conferred by KSR1 with genotoxic agents and highlight its implication in predicting chemotherapy response in breast cancer

Minimal Cuts and Genealogical Constraints on Feynman Integrals

We introduce an efficient method for deriving hierarchical constraints on the discontinuities of individual Feynman integrals. This method can be applied at any loop order and particle multiplicity, and to any configuration of massive or massless virtual particles. The resulting constraints hold to all orders in dimensional regularization, and complement the extended Steinmann relations -- which restrict adjacent sequential discontinuities -- by disallowing ordered pairs of discontinuities from appearing even when separated by (any number of) other discontinuities. We focus on a preferred class of hierarchical constraints, which we refer to as \emph{genealogical constraints}, that govern what singularities can follow from certain \emph{minimal cuts} that act as the primogenitors of the discontinuities that appear in Feynman integrals. While deriving the full set of hierarchical constraints on a given Feynman integral generally requires identifying all solutions to the (blown up) Landau equations, these genealogical constraints can be worked out with only minimal information about what singularities may appear. We illustrate the power of this new method in examples at one, two, and three loops, and provide evidence that genealogical constraints restrict the analytic structure of Feynman integrals significantly more than the extended Steinmann relations.Comment: 5 pages, 4 figures, 1 tabl

Crossing beyond scattering amplitudes

We find that different asymptotic measurements in quantum field theory can be related to one another through new versions of crossing symmetry. Assuming analyticity, we conjecture generalized crossing relations for multi-particle processes and the corresponding paths of analytic continuation. We prove them to all multiplicity at tree-level in quantum field theory and string theory. We illustrate how to practically perform analytic continuations on loop-level examples using different methods, including unitarity cuts and differential equations. We study the extent to which anomalous thresholds away from the usual physical region can cause an analytic obstruction to crossing when massless particles are involved. In an appendix, we review and streamline historical proofs of four-particle crossing symmetry in gapped theories.Comment: 108 page

What can be measured asymptotically?

We consider asymptotic observables in quantum field theories in which the S-matrix makes sense. We argue that in addition to scattering amplitudes, a whole compendium of inclusive observables exists where the time-ordering is relaxed. These include expectation values of electromagnetic or gravitational radiation fields as well as out-of-time-order amplitudes. We explain how to calculate them in two ways: by relating them to amplitudes and products of amplitudes, and by using a generalization of the LSZ reduction formula. As an application, we discuss one-loop master integrals contributing to gravitational radiation in the post-Minkowski expansion, emphasizing the role of classical cut contributions and highlighting the different infrared physics of in-in observables.Comment: 67 pages, typos correcte