自制IPS-Empress2铸瓷快速包埋材料的膨胀特性研究

IPS—Empress2铸瓷是国内外广泛应用的全瓷修复系统。为取代昂贵的进口专用包埋材料，国内已自制出与之相配套的快速包埋材料。本文研究的是其最关键的膨胀特性。采用千分尺位移计和热机械分析仪，分别测量了进口专用快速包埋材料和自制快速包埋材料的凝固膨胀及热膨胀性能，进行了统计分析和比较。结果显示，进口专用快速包埋材料的凝固膨胀率、热膨胀率和总膨胀率分别为0．858％、1．11％和1．17％；自制包埋材料的上述指标分别为0．798％、1．09％和1．16％，三项指标均无统计学差异，表明自制快速包埋材料的膨胀性能指标接近IPS—Empress2专用快速包埋材料，能满足IPS—Empress2铸瓷精密铸造的要求。     

Heart rate variability at different thermal comfort levels

The mechanism of human thermal comfort is important for building a comfortable and healthy indoor environment. This paper analyzes human heart rate variability (HRV) at different thermal comfort levels and discusses the mechanism of human thermal comfort. A total of 33 subjects were divided in 3 groups. Under air temperatures of 21, 24, 26, 28, 29, and 30°C, the subjects’ electrocardiogram was recorded for 5 min. HRV (the ratio of absolute powers in low- and high-frequency bands, LF/HF ratio) was analyzed. LF/HF at discomfort level were significantly higher than that at comfort level (P < 0.05), despite the same thermal sensation. The results indicate that sympathetic activity plays an important role in subjects’ thermal discomfort and the LF/HF ratio may be used as an indicator for human thermal comfort.     

Development of high refractive ZnS/PVP/PDMAA hydrogel nanocomposites for artificial cornea implants

A series of high refractive index (RI) ZnS/PVP/PDMAA hydrogel nanocomposites containing ZnS nanoparticles (NPs) were successfully synthesized via a simple ultraviolet-light-initiated free radical co-polymerization method. The average diameter of the ZnS NPs is ∼3 nm and the NPs are well dispersed and stabilized in the PVP/PDMAA hydrogel matrix up to a high content of 60 wt.% in the hydrogel nanocomposites. The equilibrium water content of ZnS/PVP/PDMAA hydrogel nanocomposites varied from 82.0 to 66.8 wt.%, while the content of mercaptoethanol-capped ZnS NPs correspondingly varied from 30 to 60 wt.%. The resulting nanocomposites are clear and transparent and their RIs were measured to be as high as 1.58–1.70 and 1.38–1.46 in the dry and hydrated states, respectively, which can be tuned by varying the ZnS NPs content. In vitro cytotoxicity assays suggested that the introduction of ZnS NPs added little cytotoxicity to the PVP/PDMAA hydrogel and all the hydrogel nanocomposites exhibited minimal cytotoxicity towards common cells. The hydrogel nanocomposites implanted in rabbit eyes can be well tolerated over 3 weeks. Hence, the high RI ZnS/PVP/PDMAA hydrogel nanocomposites with adjustable RIs developed in this work might potentially be a candidate material for artificial corneal implants.     

Effect of substrate thermal resistance on space-domain microchannel fluorescent melting curve analysis

In recent years, Fluorescent Melting Curve Analysis (FMCA) has become an almost ubiquitous feature of commercial quantitative PCR (qPCR) thermal cyclers. Here a micro-fluidic device is presented capable of performing FMCA within a microchannel. The device consists of modular thermally conductive blocks which can sandwich a microfluidic substrate. Opposing ends of the blocks are held at differing temperatures and a linear thermal gradient is generated along the microfluidic channel. Fluorescent measurements taken from a sample as it passes along the micro-fluidic channel permits fluorescent melting curves to be generated. In this study we measure DNA melting temperature from two plasmid fragments. The effects of flow velocity and ramp-rate are investigated, and measured melting curves are compared to those acquired from a commercially available PCR thermocycler.     

Nuchal cord: impact of umbilical artery Doppler indices on intrapartum and neonatal outcomes: a prospective cohort study

Background/objective: The purpose of this study is to investigate the use of a more biologic parameter for evaluation of the effect of nuchal cord tightness; the study of blood flow in the umbilical arteries of nuchal cord using Doppler ultrasonography.

Methods: This prospective cohort study was conducted at Ain Shams University Maternity Hospital, Cairo, Egypt in the period between August 2015 and August 2017. Hundred primigravidas were recruited with nuchal cord diagnosed by Doppler ultrasonography; whereas the rest of the study population was included in the “Control group”. Doppler velocimetry study was then performed on a free-floating loop of the umbilical cord and Doppler indices were calculated. Both groups were followed up during labor: intrapartum events, mode of delivery, and neonatal outcome were recorded.

Results: Intrapartum fetal heart rate abnormalities were significantly more common in the nuchal cord group compared to the control group. The overall cardiotocography category was significantly more commonly reflecting abnormal fetal heart rate patterns in the nuchal cord group compared to the control group with 46.74% of the nuchal group patients falling within the “suspicious – pathological – need urgent intervention” categories. Intervention rate was significantly higher in the nuchal cord group than the control group (33.69 versus 21.84%). Moreover, incidence of intrapartum fetal heart rate abnormalities and intervention rate were significantly higher in the nuchal cord with abnormal Doppler subgroup compared to both nuchal cord with normal Doppler subgroup and the control group; with a calculated number needed to harm of 2.11.

Conclusions: In view of these results, it might be concluded that umbilical cord tightness affecting fetal hemodynamics (expressed by changes in umbilical artery Doppler) might be a determinate factor affecting the intrapartum course.     

The relation between left ventricular diastolic indices and serum ferritin in thalassemia major

Iron-induced heart failure is the primary cause of death in thalassemia major patients who receive continuous transfusions. Recent studies have suggested that diastolic function is impaired prior to systolic function in process of hemochromatosis, but they did not come to agreement on the first impaired diastolic index. Additionally, serum ferritin concentration is not a reliable indicator of body iron storage since it increases in any simple inflammation. Accordingly, the authors undertook this study to assess any association between left ventricular diastolic indices and serum ferritin in thalassemic patients with normal systolic function to estimate the true amount of body iron storage and correct it in earlier stages. Serum ferritin concentration and diastolic indices were measured in 29 patients with normal left ventricular systolic function. Linear regression test was used to find any association between hematological and cardiac factors. No significant association was found between diastolic indices and serum ferritin concentration. But the results were quite different in patients above and below 15 years of age; standardized coefficients (r) for peak of E and A were increased in patients above 15, and the significance was close to .05, unlike those of younger group. Although no correlation was found between serum ferritin and diastolic indices, the results were noteworthy in patients above 15. To appropriately judge this relation, the study must be continued with a bigger sample size and having patients' mean serum ferritin concentration during the 2 past years.     

Individual factors and physical work load in relation to sensory thresholds in a middle-aged general population sample

The aim of this study was to explore individual and occupational factors possibly related to sensory thresholds in 484 middle-aged men and women from the general population. Multivariate analyses were performed using a linear model including eight covariates (age, body height, skin temperature, smoking habits, musculoskeletal symptoms during the last week before examination, isometric muscle strength, aerobic capacity, and average physical work load during the last 15 years). Men and women were considered separately in all analyses. Major findings were as follows: pressure pain thresholds increased with muscle strength; cold perception thresholds on the foot improved with increasing skin temperature; vibration and warm perception thresholds on the foot increased with age and body height; pressure pain threshold on the leg was decreased and vibration threshold on the hand was increased in women with musculoskeletal symptoms; pressure pain thresholds were slightly increased in men reporting long-lasting high physical work load. Significant sex differences were found for the majority of sensory thresholds, that is higher thresholds in men. However, body height was found to be more important than gender for differences in vibration and warm perception thresholds on the foot. Electronic Publication     

Mean Platelet Volume (MPV), Platelet Distribution Width (PDW), Platelet Count and Plateletcrit (PCT) as predictors of in-hospital paediatric mortality: a case-control Study

BackgroundThrombocytopenia has been shown to predict mortality. We hypothesize that platelet indices may be more useful prognostic indicators. Our study subjects were children one month to 14 years old admitted to our hospital.AimTo determine whether platelet count, plateletcrit (PCT), mean platelet volume (MPV) and platelet distribution width (PDW) and their ratios can predict mortality in hospitalised children.MethodsChildren who died during hospital stay were the cases. Controls were age matched children admitted contemporaneously. The first blood sample after admission was used for analysis. Receiver operating characteristic (ROC) curve was used to identify the best threshold for measured variables and the ratios studied. Multiple regression analysis was done to identify independent predictors of mortality.ResultsForty cases and forty controls were studied. Platelet count, PCT and the ratios of MPV/Platelet count, MPV/PCT, PDW/Platelet count, PDW/PCT and MPV × PDW/Platelet count × PCT were significantly different among children who survived compared to those who died. On multiple regression analysis the ratio of MPV/PCT, PDW/Platelet count and MPV/Platelet count were risk factors for mortality with an odds ratio of 4.31(95% CI, 1.69–10.99), 3.86 (95% CI, 1.53–9.75), 3.45 (95% CI, 1.38–8.64) respectively. In 67% of the patients who died MPV/PCT ratio was above 41.8 and PDW/Platelet count was above 3.86. In 65% of patients who died MPV/Platelet count was above 3.45.ConclusionThe MPV/PCT, PDW/Platelet count and MPV/Platelet count, in the first sample after admission in this case control study were predictors of mortality and could predict 65% to 67% of deaths accurately.     

Sweat pore reactivity as a surrogate measure of sympathetic nervous system activity in trauma‐exposed individuals with and without posttraumatic stress disorder

Stress analysis by FLIR (forward‐looking infrared) evaluation (SAFE) has been demonstrated to monitor sweat pore activation (SPA) as a novel surrogate measure of sympathetic nervous system (SNS) activity in a normal population. SNS responses to a series of 15 1‐s, 82 dB, white noise bursts were measured by skin conductance (SC) and SAFE monitoring of SPA on the fingers (FiP) and face (FaP) in 10 participants with posttraumatic stress disorder (PTSD) and 16 trauma‐exposed participants without PTSD (M_age = 48.92 ± 12.00 years; 26.9% female). Within participants, SC and FiP responses across trials were strongly correlated (r = .92, p < .001). Correlations between SC and FaP (r = .76, p = .001) and between FiP and FaP (r = .47, p = .005) were smaller. The habituation of SNS responses across the 15 trials was substantial (SC: d = ?2.97; FiP: d = ?2.34; FaP: d = ?1.02). There was a strong correlation between habituation effects for SC and FiP (r = .76, p < .001), but not for SC and FaP (r = .15, p = .45) or FiP and FaP (r = .29, p = .16). Participants with PTSD showed larger SNS responses to the first loud noise than those without PTSD. PTSD reexperiencing symptoms assessed by the PTSD Checklist on the day of testing were associated with the SNS responses to the first loud noise measured by SC (d = 1.19) and FiP (d = .99), but not FaP (d = .10). This study confirms convergence of SAFE and SC as valid measures of SNS activity. SAFE FiP and SC responses were highly predictive of self‐rated PTSD reexperiencing symptoms. SAFE may offer an attractive alternative for applications in PTSD and similar populations.