Operando neutron diffraction reveals mechanisms for controlled strain evolution in 3D printing

Residual stresses affect the performance and reliability of most manufactured goods and are prevalent in casting, welding, and additive manufacturing (AM, 3D printing). Residual stresses are associated with plastic strain gradients accrued due to transient thermal stress. Complex thermal conditions in AM produce similarly complex residual stress patterns. However, measuring real-time effects of processing on stress evolution is not possible with conventional techniques. Here we use operando neutron diffraction to characterize transient phase transformations and lattice strain evolution during AM of a low-temperature transformation steel. Combining diffraction, infrared and simulation data reveals that elastic and plastic strain distributions are controlled by motion of the face-centered cubic and body-centered cubic phase boundary. Our results provide a new pathway to design residual stress states and property distributions within additively manufactured components. These findings will enable control of residual stress distributions for advantages such as improved fatigue life or resistance to stress-corrosion cracking.

Health inequities around gender, disability and internal migration: are local governments doing enough

SETTING

The Kerala health system in India has more than 25 years of decentralised implementation experience. Decentralization could assist in addressing health disparities such as gender, disability, and migration.

OBJECTIVE

To explore how inequity issues comprising gender, disability and internal migrations were being addressed at present by the decentralised Kerala health system.

DESIGN

Our approach was qualitative, using document review, key informant interviews and in-depth interviews with policy makers, health staff and other stakeholders.

RESULTS

Gender aspects were incorporated into planning and budgeting, with 10% funds earmarked for women. Projects were gender-specific to women, and within conventional social roles of livelihood, welfare or reproductive health. Recently, transgender focused projects were also initiated. Schemes for people with disabilities remained welfare-centric and driven by top-down policies. The local governments performed beneficiary identification and benefit disbursal. Migrant health aspects were focused on infectious diseases surveillance and later living conditions of migrant workers.

CONCLUSION

The importance that health systems place on socioeconomic determinants of health and fundamental human rights is reflected in the health interventions for marginalised communities. In Kerala, there is now a passive application of central rules and a reluctance to utilise local platforms. Changing this is a necessary condition for achieving equal development.

Antioxidant activity of caffeic acid: thermodynamic and kinetic aspects on the oxidative degradation pathway

Caffeic acid is a phenolic secondary metabolite from plants, which is known for its antioxidant properties. The effective mitigation of methanol-induced oxidative stress by caffeic acid depends on the direct radical scavenging as well as the formation of new metabolites via oxidative degradation. Herein, thermodynamic and kinetic aspects of the oxidative degradation pathway of caffeic acid in the presence of radical CH₃O^• and its isomer, ^•CH₂OH are discussed for the first time, employing density functional theory (DFT). The direct radical scavenging activity of caffeic acid against these radicals is verified via hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. HAT is predicted to be more feasible than RAF mechanism as per the computed data. Additionally, energetic details of the proposed oxidative degradation pathway of radical adduct intermediates toward the formation of a cyclic metabolite is analyzed. Kinetic studies indicated a significant tunneling contribution to the H abstraction pathways having high activation barriers. Further, our results imply that the newly formed metabolites exhibit comparable antioxidant activity with that of caffeic acid.

Microstructure and properties of additively manufactured Al-Ce-Mg alloys

Additive manufacturing of aluminum alloys is largely dominated by a near-eutectic Al-Si compositions, which are highly weldable, but have mechanical properties that are not competitive with conventional wrought Al alloys. In addition, there is a need for new Al alloys with improved high temperature properties and thermal stability for applications in the automotive and aerospace fields. In this work, we considered laser powder bed fusion additive manufacturing of two alloys in the Al–Ce–Mg system, designed as near-eutectic (Al–11Ce–7Mg) and hyper-eutectic (Al–15Ce–9Mg) compositions with respect to the binary L → Al + Al₁₁Ce eutectic reaction. The addition of magnesium is used to promote solid solution strengthening. A custom laser scan pattern was used to reduce the formation of keyhole porosity, which was caused by excessive vaporization due to the high vapor pressure of magnesium. The microstructure and tensile mechanical properties of the alloys were characterized in the as-fabricated condition and following hot isostatic pressing. The two alloys exhibit significant variations in solidification structure morphology. These variations in non-equilibrium solidification structure were rationalized using a combination of thermodynamic and thermal modeling. Both alloys showed higher yield strength than AM Al-10Si-Mg for temperatures up to 350 °C and better strength retention at elevated temperatures than additively manufactured Scalmaloy.

Elastic constants of Ultrasonic Additive Manufactured Al 3003-H18

Ultrasonic Additive Manufacturing (UAM), also known as Ultrasonic Consolidation (UC), is a layered manufacturing process in which thin metal foils are ultrasonically bonded to a previously bonded foil substrate to create a net part. Optimization of process variables (amplitude, normal load and velocity) is done to minimize voids along the bonded interfaces. This work pertains to the evaluation of bonds in UAM builds through ultrasonic testing of a build's elastic constants. Results from ultrasonic testing on UAM parts indicate orthotropic material symmetry and a reduction of up to 48% in elastic constant values compared to a control sample. The reduction in elastic constant values is attributed to interfacial voids. In addition, the elastic constants in the plane of the Al foils have nearly the same value, while the constants normal to the foil direction have much different values. In contrast, measurements from builds made with Very High Power Ultrasonic Additive Manufacturing (VHP UAM) show a drastic improvement in elastic properties, approaching values similar to that of bulk aluminum.

Postoperative infection of an abdominal mesh due to methicillin resistant Staphylococcus aureus - a case report

Methicillin resistant Stephylococcus aureus (MRSA) infection has now become a major problem in hospitals. We present a case of postoperative infection MRSA where the primary source of the infection was found to be an abdominal mesh that was used to reinforce the abdominal wall. After one year of surgery, the patient developed wound dehiscence and discharge. MRSA was isolated from the wound, mesh, external nares, throat and axilla. Initially she was started on clindamycin and discharged from the hospital. After 5 months, patient came back to the hospital with infection at the same site. The patient was then treated with vancomycin and MRSA clearance. She responded to the treatment with complete healing of the wound and clearance of MRSA.

Atypical hyperplasia in the era of stereotactic core needle biopsy

BACKGROUND AND OBJECTIVES

To characterize both atypical hyperplasia (AH) and the malignancies typically present at open surgical biopsy in women diagnosed with AH by stereotactic core needle biopsy (SCNB).

METHODS

Patients with AH diagnosed by SCNB were advised to undergo surgical biopsy to rule out an associated malignancy. Mammography findings, pathology reports and follow-up data were analyzed.

RESULTS

AH was identified by SCNB in 38 of 893 (4.3%) patients. Carcinoma was identified in 12 of 33 (36.4%) patients who went on to surgical biopsy. Ductal carcinoma in situ (DCIS) was present in 11 of the 12 patients with malignancy. There were no characteristic mammographic findings which would identify patients with carcinoma.

CONCLUSIONS

When SCNB returns a diagnosis of AH there is a substantial risk of an associated malignancy in the breast. There appear to be no definitive criteria to distinguish which patients harbor a malignancy, and surgical biopsy should always serve as an adjunct diagnostic procedure.

Role of external electron donor in methylene blue sensitized dichromated gelatin holograms: an experimental study

An experimental study to ascertain the role of external electron donor in methylene blue sensitized dichromated gelatin (MBDCG) holograms has been carried out. The required volume holographic transmission gratings in MBDCG have been recorded using 633-nm light from a He-Ne laser. Three well-known electron donors, namely, N, N-dimethylformamide (DMF); ethylenediaminetetraacetic acid (EDTA); triethanolamine (TEA), were used in this study. The variation of diffraction efficiency (eta) as a function of light exposure (E) and concentration (C) of the electron donor under consideration was chosen as the figure of merit for judging the role of external electron donor in MBDCG holograms. A self-consistent analysis of the experimental results was carried out by recalling the various known facts about the photochemistry and the hologram formation in DSDCG and also DCG. The important findings and conclusions are as follows: (i) Each eta vs E graph is a bell-shaped curve and its peak height is influenced in a characteristic manner by the external electron donor used. (ii) High diffraction efficiency/recording speed can be achieved in pure MBDCG holograms. (iii) The diffraction efficiency/recording speed achieved in electron donor sensitized MBDCG holograms did not show any significant improvement at all over that observed in pure MBDCG holograms. (iv) In electron donor sensitized MBDCG holograms, the electron donor used, depending on its type and concentration, appears to promote the process of cross-linking of gelatin molecules in a manner to either retain or deteriorate the refractive-index modulation achieved using pure MBDCG.

The management of snake and spider bites in the southeastern United States

Of all snake bites reported in the United States of America each year, 75 per cent occur in the states that form the Southeastern Surgical Congress. Pit vipers, coral snakes, and exotic imported snakes are all found in that area. Deaths from those snake bites are rare, but morbidity is high and it is often due to overtreatment rather than undertreatment. Treatment in the field is rarely necessary for the victim who is less than 1 hour away from definitive care. The type and size of the snake and the age, size, and health of the patient are important guides to therapy. Envenomation may not occur. When envenomation occurs from pit viper bites, antivenom is not always necessary, and its inherent dangers (serum sickness and possible hypersensitivity) must be weighed against the severity of systemic and local manifestations. All coral snake bites resulting in envenomation must be treated vigorously with coral snake antivenom. The Oklahoma City Poison Control Center can guide the treatment of bites from exotic snakes. The most frequently encountered toxic spider bites in the Southeast are those of the black widow and brown recluse spiders. The symptoms of black widow envenomation are best controlled with calcium gluconate or a muscle relaxant. Antivenom should be reserved for severe reactions. Brown recluse necrotic lesions are best controlled with dapsone.