Resolutions of C^n/Z_n Orbifolds, their U(1) Bundles, and Applications to String Model Building

We describe blowups of C^n/Z_n orbifolds as complex line bundles over CP^{n-1}. We construct some gauge bundles on these resolutions. Apart from the standard embedding, we describe U(1) bundles and an SU(n-1) bundle. Both blowups and their gauge bundles are given explicitly. We investigate ten dimensional SO(32) super Yang-Mills theory coupled to supergravity on these backgrounds. The integrated Bianchi identity implies that there are only a finite number of U(1) bundle models. We describe how the orbifold gauge shift vector can be read off from the gauge background. In this way we can assert that in the blow down limit these models correspond to heterotic C^2/Z_2 and C^3/Z_3 orbifold models. (Only the Z_3 model with unbroken gauge group SO(32) cannot be reconstructed in blowup without torsion.) This is confirmed by computing the charged chiral spectra on the resolutions. The construction of these blowup models implies that the mismatch between type-I and heterotic models on T^6/Z_3 does not signal a complication of S-duality, but rather a problem of type-I model building itself: The standard type-I orbifold model building only allows for a single model on this orbifold, while the blowup models give five different models in blow down.Comment: 1+27 pages LaTeX, 2 figures, some typos correcte

An observational study to inform potential drowning intervention strategies among fishing communities in the lake zone of Tanzania (DRIFT)

Lake Victoria, Africa's largest lake, is surrounded by an abundance of lakeside communities and supports a huge fishing industry. A recent study in Uganda suggested that drowning is a common threat within these communities. Perceived risk of drowning among fisher-folk on Lake Victoria is high, and possibly of greater concern than Human Immunodeficiency Virus (HIV) infection. Yet anecdotal evidence from Tanzanian communities suggests that risky behaviours associated with drowning are common practice. DRIFT was a mixed-methods study. We first obtained estimates of the drowning incidence among the lake-side communities by collecting data on all deaths occurring in each community over the past two years. Second, data on risk factors associated with drowning, risky behaviours in the fishing communities, perceived health risks and threats, and perceptions of potential interventions were collected from fishermen and the wider communities at eight lakeside fishing villages through structured surveys/questionnaires, in-depth interviews, focus group discussions, in-depth death reviews and observational analyses of behaviour. Preliminary data on social and economic impacts of drowning deaths were collected by interviewing family members and colleagues of victims

Drowning among fishing communities on the Tanzanian shore of lake Victoria: a mixed-methods study to examine incidence, risk factors and socioeconomic impact.

OBJECTIVES: To estimate the incidence of unintentional fatal drowning and describe associated risk factors among Lake Victoria fishing communities, and to assess perceived social, financial and other impacts among families and colleagues of persons who drowned. DESIGN: A retrospective, observational mixed-methods study, conducted between September 2017 and February 2018. SETTING: Eight Tanzanian fishing communities on Lake Victoria. PARTICIPANTS: Persons who drowned in the preceding 24 months were identified using an extensive community networking approach. Adult family members, colleagues or community members familiar with the habits and behaviours of people who drowned and/or circumstances of drowning incidents participated in surveys (n=44) and in-depth interviews (n=22). MAIN OUTCOME MEASURES: Pooled drowning incidence, with sensitivity analyses allowing for uncertainties in population estimates. Risk factors were identified through the evaluation of behavioural characteristics of persons who drowned and circumstances of drowning incidents. Perceived socioeconomic impacts were assessed through semi-structured interviews with their family members and colleagues. RESULTS: The estimated drowning incidence was 217/100 000 person-years (95% CI 118 to 425/100 000). Of 86 victims identified, 70 (81%) were fishermen (79% aged 18-40 years; all men) and 9 were children (all ≤10 years). All deaths occurred in the lake. Most adults (65/77; 84%) were fishing from a boat when they drowned; 57/77 (74%) died in the evening (from ~5 pm) or at night. Six children (67%) drowned while swimming/playing at the lakeshore unsupervised. Few victims (2/86; 2%) were wearing a life jacket at the time of death. Reported socioeconomic impacts of these deaths ranged from income loss to family break-up. CONCLUSIONS: Drowning is a significant risk in Tanzanian lakeside fishing communities, with estimated mortality exceeding national incidence rates of fatal malaria, tuberculosis or HIV, but preventative strategies appear uncommon. Socioeconomic impact at the family level may be substantial. Intervention strategies are required to reduce the drowning burden among this neglected at-risk population

RG flows from Spin(7), CY 4-fold and HK manifolds to AdS, Penrose limits and pp waves

We obtain explicit realizations of holographic renormalization group (RG) flows from M-theory, from E^{2,1} \times Spin(7) at UV to AdS_4 \times \tilde{S^7} (squashed S^7) at IR, from E^{2,1} \times CY4 at UV to AdS_4 \times Q^{1,1,1} at IR, and from E^{2,1} \times HK (hyperKahler) at UV to AdS_4 \times N^{0,1,0} at IR. The dual type IIA string theory configurations correspond to D2-D6 brane systems where D6 branes wrap supersymmetric four-cycles. We also study the Penrose limits and obtain the pp-wave backgrounds for the above configurations. Besides, we study some examples of non-supersymmetric and supersymmetric flows in five-dimensional gauge theories.Comment: 42 pages, 6 eps figures, typos and misprints correcte

Supercoset CFT's for String Theories on Non-compact Special Holonomy Manifolds

We study aspects of superstring vacua of non-compact special holonomy manifolds with conical singularities constructed systematically using soluble N = 1 superconformal field theories (SCFT's). It is known that Einstein homogeneous spaces G/H generate Ricci flat manifolds with special holonomies on their cones R_+ x G/H, when they are endowed with appropriate geometrical structures, namely, the Sasaki-Einstein, tri-Sasakian, nearly Kahler, and weak G_2 structures for SU(n), Sp(n), G_2, and Spin(7) holonomies, respectively. Motivated by this fact, we consider the string vacua of the type: R^{d-1,1} x (N = 1 Liouville) x (N=1 supercoset CFT on G/H) where we use the affine Lie algebras of G and H in order to capture the geometry associated to an Einstein homogeneous space G/H. Remarkably, we find the same number of spacetime and worldsheet SUSY's in our ``CFT cone'' construction as expected from the analysis of geometrical cones over G/H in many examples. We also present an analysis on the possible Liouville potential terms (cosmological constant type operators) which provide the marginal deformations resolving the conical singularities.Comment: 60 pages, no figure, 2 tables; v2 typos correcte

Geometric Transitions on non-Kaehler Manifolds

This article is based on the author's PhD--thesis. We study geometric transitions on the supergravity level using the basic idea of arXiv:hep-th/0403288, where a pair of non-Kaehler backgrounds was constructed, which are related by a geometric transition. Here we embed this idea into an orientifold setup as suggested in arXiv:hep-th/0511099. The non-Kaehler backgrounds we obtain in type IIA are non-trivially fibered due to their construction from IIB via T-duality with Neveu-Schwarz flux. We demonstrate that these non-Kaehler manifolds are not half-flat and show that a symplectic structure exists on them at least locally. We also review the construction of new non-Kaehler backgrounds in type I and heterotic theory as proposed in arXiv:hep-th/0408192. They are found by a series of T- and S-duality and can be argued to be related by geometric transitions as well. A local toy model is provided that fulfills the flux equations of motion in IIB and the torsional relation in heterotic theory, and that is consistent with the U-duality relating both theories. For the heterotic theory we also propose a global solution that fulfills the torsional relation because it is similar to the Maldacena-Nunez background.Comment: 127 pages, based on PhD-thesis, v2 some references added, this version to appear in Fort. Phy

Mechanisms of Fasting-Mediated Protection against Renal Injury and Fibrosis Development after Ischemic Acute Kidney Injury

Ischemia-reperfusion injury of the kidney may lead to renal fibrosis through a combination of several mechanisms. We recently demonstrated that fasting protects the rat kidney against oxidative stress and mitochondrial dysfunction in early acute kidney injury, and also against fibrosis development. Here we show that preoperative fasting preserves redox status and mitochondrial homeostasis at the chronic phase of damage after severe ischemia. Also, the protective effect of fasting coincides with the suppression of inflammation and endoplasmic reticulum stress, as well as the down-regulation of the mechanistic target of rapamycin (mTOR) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways in the fibrotic kidney. Our results demonstrate that fasting targets multiple pathophysiological mechanisms to prevent renal fibrosis and damage that results after renal ischemia-reperfusion injury

Down-Regulation of Interleukin-8 Secretion from Mycobacterium tuberculosis-Infected Monocytes by Interleukin-4 and -10 but Not by Interleukin-13

Interleukin-8 (IL-8), a CXC chemokine, has a central role in leukocyte recruitment to areas of granuloma formation in tuberculosis. In the present studies, we investigated the effect of the T(H)2-derived cytokines IL-4, IL-10, and IL-13 on Mycobacterium tuberculosis-induced IL-8 secretion from purified human monocytes. Our results demonstrate that IL-4 and IL-10 have a down-regulatory effect on IL-8 secretion and that this effect is dose dependent. IL-10 has a greater effect than IL-4 on secretion, and autologous IL-10 secreted from M. tuberculosis-infected monocytes also down-regulates IL-8 secretion. The down-regulatory effect is partly a result of reduced IL-8 mRNA accumulation analyzed by reverse transcription-PCR. When combined, 1 μM IL-4 and IL-10 had an additive effect in decreasing IL-8 secretion and transcription; there was no synergy of action. IL-13 did not have any significant effect on IL-8 gene expression or secretion. The inhibitory effect of IL-10 but not of IL-4 is associated with decreased nuclear binding of the key activating transcription factor NF-κB. We show for the first time that M. tuberculosis causes up-regulation of nuclear binding of Oct-1 detected by electromobility gel shift assay. However, neither AP-1 nor Oct-1 nuclear binding was altered by IL-4 or IL-10. In summary, this study demonstrates that type 2 responses have an important role in the regulation of M. tuberculosis-induced IL-8 expression but that the mechanisms by which the different cytokines act are distinct