Low Backside Research Articles

Co‐optimizing compressive and heat‐insulation properties of rigid fibrous ceramics by compositing with phenolic aerogel

AbstractLow compressive strength of rigid fibrous ceramics (RFC) greatly restricts their application as thermal protection materials. Traditional reinforcing method using ceramic aerogels shows low efficiency and impairs high‐temperature thermal‐insulation properties. Herein, a novel strategy is proposed to optimize compressive and high‐temperature thermal‐insulation performances of RFC enormously and synergistically using nanoporous phenolic aerogel as reinforcement and high‐temperature evaporative refrigerant. In‐situ X‐ray micro‐CT results reveal that phenolic aerogel can protect bonding areas and handle compressive deformation, thereby increasing compressive strength of RFC. What's more, the strengthening effect along practical application (through‐thickness) direction is more obvious than that along in‐plane direction. Ablation test results indicate that pyrolysis gas of phenolic will carry away surface heat, thus improving high‐temperature thermal‐insulation and antiablation performances. The resulting mullite RFC with 45 wt.% of phenolic aerogel exhibits a high compressive strength of 44.8 ± 1.1 MPa along through‐thickness direction, low backside temperature of 38.4°C under ablation temperature of 1500°C for 30 s. The idea and results will further advance the application of RFC in more extreme environments.

Low back pain among professional bus drivers: a cross-sectional study from Bangladesh

BackgroundLow back pain (LBP) is a common condition contributing to impaired quality of life among professional vehicle drivers. Our study aimed to assess LBP prevalence and associated factors among professional bus drivers in Bangladesh.MethodsA cross-sectional study was conducted among 368 professional bus drivers using a semi-structured questionnaire. A Nordic Musculoskeletal Questionnaire (NMQ) subscale was used to measure LBP. Multivariable logistic regression analysis was used to identify the factors associated with LBP.ResultsIn the last month, 127 (34.51%) participants reported experiencing pain or discomfort in the lower backside. Multivariable logistic regression analysis showed that age of more than 40 years (adjusted odds ratio (aOR): 2.07, 95% confidence interval (CI): 1.14 to 3.75), the income of more than 15,000 BDT per month (aOR: 1.91, 95% CI: 1.11 to 3.26), work duration more than ten years (aOR: 2.53, 95% CI: 1.12 to 5.70), working more than 15 days per month (aOR: 1.93, 95% CI: 1.02 to 3.65), working more than 10 h per day (aOR: 2.46, 95% CI: 1.05 to 5.75), poor condition of the driving seat (aOR: 1.80, 95% CI: 1.08 to 3.02), current smoking habit (aOR: 9.71, 95% CI: 1.25 to 75.15), illicit substances use (aOR: 1.97, 95% CI: 1.11 to 3.48), and four hours or less sleeping time per day (aOR: 1.83, 95% CI: 1.09 to 3.06) were positively associated with LBP.ConclusionThe high burden of LBP among the participants calls for a focus on this vulnerable group's occupational health and safety, with particular emphasis on implementing standard measures.

Thermo‐Responsive Self‐Ceramifiable Robust Aerogel with Exceptional Strengthening and Thermal Insulating Performance at Ultrahigh Temperatures

AbstractHigh‐performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo‐responsive self‐ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high‐strength semi‐crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several‐fold (from 0.739 to 2.726 MPa). The self‐ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self‐ceramifiable capacity enables aerogels to provide fire resistance, high‐strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack‐free overall structure, and invariant porous morphology. This self‐ceramifiable aerogel opens up a new avenue for developing thermal‐protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments.

A Complex Fistula-in-Ano Presenting As A Sinus Right Side of Lower Back

A Complex Fistula-in-Ano Presenting As A Sinus Right Side of Lower Back

Unusual Giant Syringomyelia with Neurocutaneous Melanosis

A two year old male presented with feeding intolerance and lethargy. Mother had normal delivery with term baby. The patient denied previous trauma or recent weight loss. Physical examination revealed neurocutaneous melanosis (NCM) over lower back side of body and no signs of peripheral motor deficit or abnormal reflexes. Hematological investigations showed no abnormality. Magnetic resonance (MR) imaging found a large, cystic cavity that was eccentric in the cervicothoracic spine extending from C3 to L1. Suboccipital decompressive craniectomy, bilateral C1 laminectomy, and occipital duraplasty were done. J Nepal Paediatr Soc 2014;34(3):250-251 DOI: http://dx.doi.org/10.3126/jnps.v34i3.11165

Giant melanoacanthoma mimicking malignant melanoma

Melanoacanthoma denotes a rare variant of pigmented seborrheic keratosis. A 65-year-old male farmer had pigmented, verrucous, itchy, highly painful, progressively growing irregularly oval plaque on left side of lower back for the past five years. The indurated lesion, measuring maximum diameter 10 cm × 5 cm, had no discharge, bleeding, ulceration, or associated lymphadenopathy. Dermoscopy showed regular pigmentary network and cribiform pattern of ridges without any feature of malignant melanoma. Histopathology showed well-defined islands of basaloid cells interspersed with large and richly dendritic melanocytes. The lesion was totally excised followed by skin grafting. Our patient was unique in its massive size and clinical resemblance with malignant melanoma. The diagnosis was confirmed by dermoscopy and skin biopsy.

A New High-Gain Microstrip Yagi Array Antenna With a High Front-to-Back (F/B) Ratio for WLAN and Millimeter-Wave Applications

A new printed microstrip Yagi array antenna is proposed that can achieve a high gain and low backside radiation for various applications up to the millimeter-wave frequency range. The high front-to-back (F/B) ratio (up to 15 dB) is attributed to the constructive interference that takes place between the individual printed Yagi arrays in the design. Through the spacing of the elements, the directivity (between 9-11.5 dBi) and the F/B ratio can be altered to suit the application of interest. The operational principles of this design are discussed to give insight on the radiation mechanism of the antenna. An initial design at around 32.5 GHz is presented to show the performance capabilities of this configuration. An impedance bandwidth of 8.3% can be achieved around this frequency. Then, a parametric analysis is conducted to estimate the significance of the design parameters that affect the antenna's performance. Finally, measured return loss and radiation pattern performance at 5.2 GHz is displayed to validate the principles and simulated results of the design. The measured impedance bandwidth of 10% is achieved. The F/B ratio is 15 dB which is larger than values previously published by 5-10 dB. Additionally, a gain of 10.7 dBi is observed. To the author's knowledge, this is the first microstrip Yagi array antenna presented that has a high gain and a high F/B ratio designed using simple fabrication techniques

Determination of the Orientation of Adsorbed Cytochromecon Carboxyalkanethiol Self-Assembled Monolayers by In Situ Differential Modification

The contact domain utilized by horse cytochrome c when adsorptively bound to a C(10)COOH self-assembled monolayer (SAM) was delineated using a chemical method based on differential modification of surface amino acids. Horse cytochrome c was adsorbed at low ionic strength (pH 7.0, 4.4 mM potassium phosphate) onto 10 microm diameter gold particles coated with HS(CH(2))(10)COOH SAMs. After in situ modification of lysyl groups by reductive Schiff-base methylation, the protein was desorbed, digested using trypsin, and the peptide mapped using LC/MS. Relative lysyl reactivities were ascertained by comparing the resulting peptide frequencies to control samples of solution cytochrome c modified to the same average extent. The least reactive lysines in adsorbed cytochrome c were found to be 13, 72, 73, 79, and 86-88, consistent with a contact region located up and to the left (Met-80 side) of the solvent-exposed heme edge (conventional front face view). The most reactive lysines were 39, 53, 55, and 60, located on the lower backside. The proposed orientation features a heme tilt angle of approximately 35-40 degrees with respect to the substrate surface normal. Factors that can complicate or distort data interpretation are discussed, and the generality of differential modification relative to existing in situ methods for protein orientation determination is also addressed.

Backside Wear Is Low in Retrieved Modern, Modular, and Nonmodular Acetabular Liners

Modern modular components with maximized conformity between liner and shell, improved locking mechanisms, and smooth inner surfaces should have less backside wear than first-generation modular designs. Also, nonmodular components should show no backside wear in vivo. We compared the backside wear of retrieved liners from nonmodular and modular components from first-generation and second-generation designs. We matched for time in situ, patient age and weight for nine retrieved Harris-Galante Type 1 liners, nine Harris-Galante Type 2 liners, nine Trilogy liners, and nine Implex nonmodular liners. The backside of the liners was divided in quadrants, examined under a x10 binocular loupe, and rated by a score of 0 (absence of wear) to 3 (severe backside wear) for a total ranging from 0 to 12. The average total backside wear score was 8.4 for the Harris-Galante Type 1 liner, 7.3 for the Harris-Galante Type 2 liner, 3.7 for the Trilogy liner, and 2.3 for the Implex liner. We observed a significant reduction in the backside wear of modern modular and nonmodular acetabular components (Trilogy(R) and Implex) when compared with first-generation modular designs (Harris-Galante Types 1 and 2). Nonmodular acetabular cups had a low backside wear in vivo. Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

Evaluation of rapid thermal processing systems for use in CMOS fabrication

The role of rapid thermal processes (RTP) is evolving to meet the demands of next generation complementary metal oxide semiconductors technology. The purpose of this paper is to describe three modern RTP systems and evaluate them in terms of their process capability on control wafers, throughput, and cost of ownership. Tool A is a RTP system equipped with wafer rotation and multiple pyrometer based temperature control system to optimize within wafer uniformity during soak and spike anneals. Tool A has 1–2 °C of run to run temperature variation. Tool A also has 2–3 °C of within wafer variation for soak anneals as shown by arsenic and boron implanted control wafers. During emissivity independence testing, Tool A showed higher sheet resistivity values for low backside emissivity test wafers than high emissivity wafers. Emissivity independence testing for Tool A and Tool B (ripple pyrometry based tool) shows similar results as shown by difference of about 2 Ω/□ between high and low emissivity wafers on soak and spike anneal processes. Tool B shows about 1–2 and 7–9 °C of within wafer temperature variation for soak and spike anneal respectively. Tool C (hot liner based tool) is feasible to be used for older technologies at about 0.25 μm as it has a wider process window for temperature control and higher within wafer uniformity. This stems from the fact that the pyrometer views the hot liner and deduces wafer temperature. Run to run variation for this system ranges about 5–7 °C and within wafer temperature variation is about 8–10 °C. Tool A has the highest cost of ownership (almost four times as much as of Tool B). Tool A has two and half times the throughput as of Tool B. Tool B and Tool A are similar in process capability study as shown by sheet resistivity based control wafers. Tool A has an additive advantage of detecting “bare” silicon temperature even at low temperature region of 400–700 °C due to small operating wavelength of its pyrometer. Tool B's ripple pyrometer does not sense the “bare” silicon wafer radiation until it reaches 700 °C. Tool B has throughput of about 30–40 wafers/h for standard soak anneals. Tool C is most cost effective tool but does not meet requirements for manufacturing technologies beyond 0.25 μm. Its capacity is about 25 wafers/h for soak anneals.