Symmetry Constraints in Inflation, α\alpha-vacua, and the Three Point Function

The Ward identities for conformal symmetries in single field models of inflation are studied in more detail in momentum space. For a class of generalized single field models, where the inflaton action contains arbitrary powers of the scalar and its first derivative, we find that the Ward identities are valid. We also study a one-parameter family of vacua, called $\alpha$-vacua, which preserve conformal invariance in de Sitter space. We find that the Ward identities, upto contact terms, are met for the three point function of a scalar field in the probe approximation in these vacua. Interestingly, the corresponding non-Gaussian term in the wave function does not satisfy the operator product expansion. For scalar perturbations in inflation, in the $\alpha$-vacua, we find that the Ward identities are not satisfied. We argue that this is because the back-reaction on the metric of the full quantum stress tensor has not been self-consistently incorporated. We also present a calculation, drawing on techniques from the AdS/CFT correspondence, for the three point function of scalar perturbations in inflation in the Bunch-Davies vacuum.Comment: 51 pages, 3 figures, 6 appendices. v3: JHEP version. Minor typos correcte

Simplified Production of Large Prototypes using Visible Slicing

Rapid Prototyping (RP) is a totally automatic generative manufacturing technique based on a “divide-and-conquer” strategy called ‘slicing’. Simple slicing used on 2.5-axis kinematics of the existing RP machines is responsible for the staircase error. Although thinner slices will have less error, the slice thickness has practical limits. Visible Slicing overcomes these limitations. A few visible slices exactly represent the object. Each visible slice can be realized using a 3- axis kinematics machine from two opposite directions. Visible slicing is implemented on Segmented Object Manufacturing (SOM) machine under development. SOM can produce soft large prototypes faster and cheaper with accuracy comparable to that of CNC machining.Mechanical Engineerin

Techno-Economic Analysis of Hybrid Layered Manufacturing

Subtractive manufacturing (CNC machining) has high quality of geometric and material properties but is slow, costly and infeasible in some cases; additive manufacturing (RP) is just the opposite. Total automation and hence speed is achieved in RP by compromising on quality. Hybrid Layered Manufacturing (HLM) developed at IIT Bombay combines the best features of both these approaches. It uses arc welding for building near-net shapes which are finish machined to final dimensions. High speed of HLM surpasses all other processes for tool making by eliminating NC programming and rough machining. The techno-economic viability of HLM process has been proved through a real life case study. Time and cost of tool making using HLM promises to be substantially lower than that of CNC machining and other RP methods. Interestingly, the material cost in HLM was also found to be lower. HLM is a cheaper retrofitment to any 3 or 5 axis CNC milling machine or machining center.Mechanical Engineerin

Study of surgical site infection in patients undergoing caesarean section at tertiary care center, Gujarat

Background: Surgical site infection following cesarean delivery leads to increasing the duration of patient hospitalization, hospital costs and raise the burden on our healthcare system. The incidence of SSI after cesarean range from 3% to 5%. Objective of current investigation was to study the risk factor & microbial agents responsible for SSI in LSCS and impact of SSI on perinatal outcome.Methods: This prospective study was done among 324 pregnant women undergoing LSCS at department of obstetrics and Gynecology in GMERS medical college & hospital, Sola, Ahmedabad during April 2015 to April 2016. All patients were following up to 7thpostoperative day.SSI was defined by CDC criteria.Results: The incidence of SSI noted in present study was 8.02%. Almost 46.2% cases had BMI ≥25 kg/m2, 65.4% multipara, 34.6% resided in rural area of SSI group. PIH, PROM, LSCS in emergency, multiple vaginal examination (>3), perioperative blood glucose (≥110 mg/dl), duration of surgery (≥60 min), past H/O of LSCS noted in participants of SSI was 30.8%, 30.8%, 96.1, 19.3%, 84.6%, 23.1%), 73.1% respectively. Staphylococcus aureus was the most common microorganism identified and incidence of NICU admission was 11.5% in SSI group.Conclusions: Incidence of SSI in present is 8.02%. BMI, PIH, PROM, LSCS in emergency, multiple vaginal examination (>3), perioperative blood glucose (≥110 mg/dl), duration of surgery (≥60 min), Past H/O of LSCS were noted statistically significantly higher among the participants of SSI group. Staphylococcus aureus was the most common organism identified