3D Printing Thermally Stable High-Performance Polymers Based on a Dual Curing Mechanism

High-performance polymers are an important class of materials that are used in challenging conditions, such as in aerospace applications. Until now, 3D printing based on stereolithography processes can not be performed due to a lack of suitable materials. There is report on new materials and printing compositions that enable 3D printing of objects having extremely high thermal resistance, with Tg of 283 °C and excellent mechanical properties. The printing is performed by a low-cost Digital Light Processing printer, and the formulation is based on a dual-cure mechanism, photo, and thermal process. The main components are a molecule that has both epoxy and acrylate groups, alkylated melamine that enables a high degree of crosslinking, and a soluble precursor of silica. The resulting objects are made of hybrid materials, in which the silicon is present in the polymeric backbone and partly as silica enforcement particles.     

Determinants of serum polybrominated diphenyl ether (PBDE) levels among pregnant women in the CHAMACOS cohort

We measured levels of 10 polybrominated diphenyl ether (PBDE) congeners in serum collected during pregnancy and at delivery from 416 pregnant, predominantly immigrant, women living in Monterey County, CA. The most frequently detected congeners were BDE-47, -99, -100, and -153, all components of the penta mixture, detected in >97% of samples. We used multivariable regression models to examine factors associated with exposure to individual PBDE congeners as well as their total summed concentration (ng/g lipid). Prenatal and delivery total PBDE levels were correlated between sampling times (n = 21; Pearson r = 0.99, p < 0.001). In multivariable models, total PBDE levels increased significantly with time residing in the U.S. (p < 0.001) and among women with ≥3 pieces of stuffed furniture in their homes (p < 0.05). Women's total PBDE levels increased 4.0% (95% CI = 2.8, 5.3) for each additional year residing in the U.S., after adjustment for prepregnancy BMI, weight gain during pregnancy, and SES. Having ≥3 pieces of stuffed furniture in the home was associated with a 26.8% (95% CI = 2.0, 57.5) increase in women's serum PBDE levels. Findings suggest PBDE indoor contamination in California homes is contributing to human exposures in a population of recent immigrants.     

Nanoporous artificial proboscis for probing minute amount of liquids

We describe a method of fabrication of nanoporous flexible probes which work as artificial proboscises. The challenge of making probes with fast absorption rates and good retention capacity was addressed theoretically and experimentally. This work shows that the probe should possess two levels of pore hierarchy: nanopores are needed to enhance the capillary action and micrometer pores are required to speed up fluid transport. The model of controlled fluid absorption was verified in experiments. We also demonstrated that the artificial proboscises can be remotely controlled by electric or magnetic fields. Using an artificial proboscis, one can approach a drop of hazardous liquid, absorb it and safely deliver it to an analytical device. With these materials, the paradigm of a stationary microfluidic platform can be shifted to the flexible structures that would allow one to pack multiple microfluidic sensors into a single fiber.     

Upward-looking ground-penetrating radar for monitoring snowpack stratigraphy

Operational remote monitoring of snowpack stratigraphy, melt water intrusions and their evolution with time for forecasting snowpack stability is not possible to date. Determination of the spatial variability of snowpack conditions on various scales requires a number of point measurements with various methods. These methods are either destructive or do not provide information about the internal structure of the snowpack. The application of a remotely controlled non-destructive sensor system would help to gain a higher spatio-temporal resolution about information of the snowpack. In this study we present results from upward-looking ground-penetrating radar (GPR) surveys from horizontal caves dug in the front wall of snow pits at the bottom of the snowpack. GPR data are compared with vertical profiles of snow hardness and density, obtained in the snow pit. Data were acquired in different areas with varying snow conditions with various GPR impulse systems, frequencies and polarizations. Radar experiments with high frequencies (> 1 GHz) detect internal layers in the snowpack in dry snow, but fail to provide clear reflections at the upper snow-air transition because of attenuation. In wet snow, the radar signals < 1 GHz are capable to penetrate a meter-thick snowpack and detect the snow surface, although the signal is strongly attenuated. Analysis of reflection phases and magnitudes allows interpretation of their physical origin in terms of changes in electrical permittivity. Varying antenna polarization causes a strongly different signal response, likely caused by the snow-pit wall present in our set-up. Forward calculation of density-based reflection coefficients between neighboring layers of varying hardness yields ambiguous results in terms of correspondence with observed radar reflections apart except for interferences of neighboring reflections. Moreover, we identify several pitfalls for future applications. The system set-up used here represents a basis for further developments towards a system, which is capable of improving information on the spatial and temporal snowpack characteristics.     

The clinical characteristics of intraoral herpes simplex virus infection in 52 immunocompetent patients

OBJECTIVES: To determine if nonsteroidal anti-inflammatory drugs provide adequate pain control for patients having laparoscopic hernia repair and to compare the effectiveness of ketorolac tromethamine with ibuprofen in reducing postoperative laparoscopic hernia pain. DESIGN AND SETTING: Prospective double-blind randomized study at a 100-bed community hospital. PATIENTS: Seventy patients ranging in age from 16 to 83 years scheduled for elective laparoscopic inguinal hernia repair. INTERVENTIONS: Patients undergoing laparoscopic hernia repair were enrolled in a double-blind randomized study to compare the 2 treatments. Group 1 received a placebo capsule 1 hour before surgery and ketorolac tromethamine, 60 mg intravenously, at the time of trocar insertion. Group 2 received ibuprofen, 800 mg an hour before surgery, and isotonic sodium chloride solution, 2 mL intravenously, at the time of trocar insertion. In addition, all patients received local infiltration of 30 mL of bupivacaine hydrochloride into their trocar sites. All patients were discharged within 5 hours of the operation and were instructed to take 400 mg of ibuprofen orally every 4 hours for 24 hours whether or not they were experiencing pain. A 24-hour supply of ibuprofen was provided to all study patients. Pain was assessed using the Visual Analog Pain Scale with a maximum pain rating of 100. Assessments were done at the time of and 18 hours after discharge. MAIN OUTCOME MEASURE: Postoperative pain 18 and 24 hours after discharge was assessed using a standardized questionnaire in a telephone interview by a registered nurse from the Outpatient Surgical Unit. RESULTS: There was no significant difference in the level of pain experienced by 35 patients who received ketorolac intravenously and 35 who received ibuprofen orally. There was no significant difference between the 2 treatment groups in the amount of pain experienced at discharge and 18 hours after discharge. CONCLUSIONS: Pain relief from ibuprofen, 800 mg, administered orally an hour before laparoscopic hernia repair was not statistically different from that obtained with intravenous ketorolac, 60 mg, administered intraoperatively when comparing the hospital discharge pain score and the mean and highest pain scores 18 hours after discharge. Ibuprofen offers equivalent pain control at a lower cost and reduced potential for adverse drug events compared with intravenous ketorolac in patients having laparoscopic hernia repair. No patient required narcotic supplementation, and pain control was judged satisfactory by all the patients.     

Amyotrophic lateral sclerosis

The final cascade of amyotrophic lateral sclerosis (ALS) coincides with the onset of clinical neurological deficits and involves multifactorial interactive mechanisms. These terminal events include excitotoxicity, free radical accumulation and possibly immunological disturbances. They are probably predated by months or years by thus far unidentified triggers. Selective vulnerability of the corticomotneuronal system in ALS is likely due to degradation of several gene products essential to transmitter, receptor and nerve growth factor maintenance specific to this functional system. Therapeutic strategies involve neuroprotection, symptomatic and combination neuronal therapy targeted to the final cascade of ALS.     

Computer simulation of consumable melted slabs

A mathematical model has been developed to simulate two-dimensional heat flow for a slab ingot produced as a remelted product. Various heat flow parameters have been studied to determine the influence of changes in them on local solidification time. The parameters which show the greatest influence are the heat transfer coefficient and the thickness of the slab. The rate of addition of material changes the depth of the molten pool, but does not affect local solidification time.     

Principles and applications of ion beam techniques for the analysis of solids and thin films

This paper reviews in principle and by examples how a collimated mono-energetic and mono-atomic beam incident on a target provides information on its structure and composition when the energy of the back-scattered beam atoms, or of the particles generated by nuclear reactions, is analyzed. Examples are selected with particular emphasis on thin films and Si technology. For convenience, we define three different energy ranges of the incident beam (low energies from 1 to 6 keV, medium energies from 100 to 500 keV and high energies from 1 to 2 MeV) and discuss each range separately, according to the following table of contents.     

Weighted‐selective aggregated majority‐OWA operator and its application in linguistic group decision making

This paper focuses on the aggregation operations in the group decision‐making model based on the concept of majority opinion. The weighted‐selective aggregated majority‐OWA (WSAM‐OWA) operator is proposed as an extension of the SAM‐OWA operator, where the reliability of information sources is considered in the formulation. The WSAM‐OWA operator is generalized to the quantified WSAM‐OWA operator by including the concept of linguistic quantifier, mainly for the group fusion strategy. The QWSAM‐IOWA operator, with an ordering step, is introduced to the individual fusion strategy. The proposed aggregation operators are then implemented for the case of alternative scheme of heterogeneous group decision analysis. The heterogeneous group includes the consensus of experts with respect to each specific criterion. The exhaustive multicriteria group decision‐making model under the linguistic domain, which consists of two‐stage aggregation processes, is developed in order to fuse the experts’ judgments and to aggregate the criteria. The model provides greater flexibility when analyzing the decision alternatives with a tolerance that considers the majority of experts and the attitudinal character of experts. A selection of investment problem is given to demonstrate the applicability of the developed model.     

Comparing measures of model selection for penalized splines in Cox models

This article presents an application and a simulation study of model fit criteria for selecting the optimal degree of smoothness for penalized splines in Cox models. The criteria considered were the Akaike information criterion, the corrected AIC, two formulations of the Bayesian information criterion, and a generalized cross-validation method. The estimated curves selected by the five methods were compared to each other in a study of rectal cancer mortality in autoworkers. In the stimulation study, we estimated the fit of the penalized spline models in six exposure-response scenarios, using the five model fit criteria. The methods were compared on the basis of a mean squared error score and the power and size of hypothesis tests for any effect and for detecting nonlinearity. All comparisons were made across a range in the total sample size and number of cases.