High-temperature intermittent drying: quality characterization of crumb rubber

In rubber research, drying is one of the most prominent stage to preserve the material. Numerous drying studies had been conducted by industrial specialists and researchers for decades, but the difficulties in producing consistent quality rubber remained unresolved. Hot air drying is the preferred artificial drying method to produce dried crumb rubber, but the final products tends to have wet rubber trapped in the dried rubber, which was undesirable. Prolonged drying at high hot air heating temperature was typically used to prevent the wet rubber pieces in dried rubber. However, the prolonged drying period leads to severe deterioration of rubber’s properties. One way to overcome this quality problem is to apply two-stage drying techniques. The basis of this research work was to study the possibility of quality enhancement through two-stage intermittent vacuum convective drying of crumb rubber via time-varying stepwise temperature profile. The main objectives were to compare the quality and drying kinetics of crumb rubber subjected to the two-stage vacuum convective drying (VCD) techniques. The experimental strategy was started with drying the crumb rubber using vacuum drying (VD), hot air drying (HAD) and two-stage VCD. The application of two-stage VCD in rubber drying gave the shortest drying time compared to VD and HAD. It was found that the two-stage VCD gave the lowest colour change and high plasticity retention index. Thus, further experimental works were carried out based on two-stage VCD. To objectively access the quality changes of rubber, the effect of varying operating parameters, including vacuum pre-drying duration, hot air drying temperature and rubber sample diameter were investigated for two-stage continuous and intermittent VCD at high drying temperature (90 - 150°C). Their drying kinetics (drying time, drying rate, effective moisture diffusivity) and product quality (visual attributes, textural attributes) were considered. The results indicated that the drying kinetics and the overall quality results of dried rubber under two-stage intermittent VCD at high temperature performed better than the corresponding continuous tests. Using two-stage intermittent VCD, dried rubber had an acceptable colour, hardness and stickiness that required further test plan. Using a time-varying stepwise temperature profile, the rubber samples were dried sequentially with vacuum pre-drying at 90°C (30 min), followed by hot air drying at 150°C (60 min), 130°C (40 min) and 110°C (80 min). For every 15 min in the hot air convective dryer, the heat input was switched off for 5 min tempering intervals, which is intermittent ratio of 0.75. The time-varying stepwise intermittent process resulted in an acceptable colour of rubber products with moderate hardness and high stickiness. The total colour change (ΔE) values of the dried crumb rubber was 7.82, which was lowered than hot air drying and vacuum drying (12.75 and 9.93). The dried crumb rubber hardness and stickiness values were 69.42 and -27.55 g, respectively whereas continuous hot air dried crumb rubber had hardness and stickiness values of 620.69 and -140.29 g, respectively. The results indicate that the time-varying stepwise temperature profile helps in maintaining the sample temperature to prevent severe oxidative degradation to the samples. The samples tend to form impermeable rubber layer when undergone prolonged drying. The main contribution of this study is to provide comprehensive information on the high temperature drying characteristics of rubber, concerning both drying kinetics and the product quality. The effect of controllable factors such as vacuum pre-drying duration, hot air heating temperature and sample diameter were investigated for both two-stage continuous and intermittent VCD. The industry should adopt two-stage VCD approach with time varying stepwise profile for better rubber quality and shorter drying time

High-temperature intermittent drying: quality characterization of crumb rubber

In rubber research, drying is one of the most prominent stage to preserve the material. Numerous drying studies had been conducted by industrial specialists and researchers for decades, but the difficulties in producing consistent quality rubber remained unresolved. Hot air drying is the preferred artificial drying method to produce dried crumb rubber, but the final products tends to have wet rubber trapped in the dried rubber, which was undesirable. Prolonged drying at high hot air heating temperature was typically used to prevent the wet rubber pieces in dried rubber. However, the prolonged drying period leads to severe deterioration of rubber’s properties. One way to overcome this quality problem is to apply two-stage drying techniques. The basis of this research work was to study the possibility of quality enhancement through two-stage intermittent vacuum convective drying of crumb rubber via time-varying stepwise temperature profile. The main objectives were to compare the quality and drying kinetics of crumb rubber subjected to the two-stage vacuum convective drying (VCD) techniques. The experimental strategy was started with drying the crumb rubber using vacuum drying (VD), hot air drying (HAD) and two-stage VCD. The application of two-stage VCD in rubber drying gave the shortest drying time compared to VD and HAD. It was found that the two-stage VCD gave the lowest colour change and high plasticity retention index. Thus, further experimental works were carried out based on two-stage VCD. To objectively access the quality changes of rubber, the effect of varying operating parameters, including vacuum pre-drying duration, hot air drying temperature and rubber sample diameter were investigated for two-stage continuous and intermittent VCD at high drying temperature (90 - 150°C). Their drying kinetics (drying time, drying rate, effective moisture diffusivity) and product quality (visual attributes, textural attributes) were considered. The results indicated that the drying kinetics and the overall quality results of dried rubber under two-stage intermittent VCD at high temperature performed better than the corresponding continuous tests. Using two-stage intermittent VCD, dried rubber had an acceptable colour, hardness and stickiness that required further test plan. Using a time-varying stepwise temperature profile, the rubber samples were dried sequentially with vacuum pre-drying at 90°C (30 min), followed by hot air drying at 150°C (60 min), 130°C (40 min) and 110°C (80 min). For every 15 min in the hot air convective dryer, the heat input was switched off for 5 min tempering intervals, which is intermittent ratio of 0.75. The time-varying stepwise intermittent process resulted in an acceptable colour of rubber products with moderate hardness and high stickiness. The total colour change (ΔE) values of the dried crumb rubber was 7.82, which was lowered than hot air drying and vacuum drying (12.75 and 9.93). The dried crumb rubber hardness and stickiness values were 69.42 and -27.55 g, respectively whereas continuous hot air dried crumb rubber had hardness and stickiness values of 620.69 and -140.29 g, respectively. The results indicate that the time-varying stepwise temperature profile helps in maintaining the sample temperature to prevent severe oxidative degradation to the samples. The samples tend to form impermeable rubber layer when undergone prolonged drying. The main contribution of this study is to provide comprehensive information on the high temperature drying characteristics of rubber, concerning both drying kinetics and the product quality. The effect of controllable factors such as vacuum pre-drying duration, hot air heating temperature and sample diameter were investigated for both two-stage continuous and intermittent VCD. The industry should adopt two-stage VCD approach with time varying stepwise profile for better rubber quality and shorter drying time

Mobile phone dependence, social support and impulsivity in Chinese university students

This study examined the frequency of mobile phone dependence in Chinese university students and explored its association with social support and impulsivity. Altogether, 909 university students were consecutively recruited from a large university in China. Mobile phone use, mobile phone dependence, impulsivity, and social support were measured with standardized instruments. The frequency of possible mobile phone use and mobile phone dependence was 78.3% and 7.4%, respectively. Multinomial logistic regression analyses revealed that compared with no mobile phone dependence, possible mobile phone dependence was significantly associated with being male (p = 0.04, OR = 0.7, 95% CI: 0.4–0.98), excessive mobile phone use (p \u3c 0.001, OR = 1.2, 95% CI: 1.09–1.2), and impulsivity (p \u3c 0.001, OR = 1.05, 95% CI: 1.03–1.06), while mobile phone dependence was associated with length of weekly phone use (p = 0.01, OR = 2.5, 95% CI: 1.2–5.0), excessive mobile phone use (p \u3c 0.001, OR = 1.3, 95% CI: 1.2–1.4), and impulsivity (p \u3c 0.001, OR = 1.08, 95% CI: 1.05–1.1). The frequency of possible mobile phone dependence and mobile phone dependence was high in this sample of Chinese university students. A significant positive association with impulsivity was found, but not with social support

Review of food toxicological issues associated in rubber products

Over the centuries, rubber latex gained its popularity in machinery application due to its unique thermal properties, high elasticity and excellent impact resistance. It is widely accepted in food industry as rubber has good resistance to chemicals, including acids, alkalis and salts. For instance, rubber components comprise of couplings, shields, dust covers, gaskets and seals exist as group or standalone component in food manufacturing equipments or machinery. Even though most of the rubber based products in food industry fulfil the requirements of Food and Drug Administration (FDA), however, the presence of trace amount of chemicals upon the preceding processing of rubber might accidentally contaminate to the food products. The contamination that happened might caused changes in food quality in term of taste, smell or even visual appearance. Therefore, this paper aims to review some of the manufacturing process of natural rubber products and to understand the possibility of extractable and leachable contaminated food products. An overview of potential toxicological problems will be discussed and the finding will be summarized in this paper

The psychometric properties of the quick inventory of depressive symptomatology-self-report (QIDS-SR) in patients with HBV-related liver disease

Background: Comorbid depression in Hepatitis B virus (HBV) is common. Developing accurate and time efficient tools to measure depressive symptoms in HBV is important for research and clinical practice in China. Aims: This study tested the psychometric properties of the Chinese version of the 16-item Quick Inventory of Depressive Symptomatology (QIDS-SR) in HBV patients. Methods: The study recruited 245 depressed patients with HBV and related liver disease. The severity of depressive symptoms was assessed with the Montgomery-Asberg Depression Rating Scale (MADRS) and the QIDS-SR. Results: Internal consistency (Cronbach’s alpha) was 0.796 for QIDS-SR. The QIDS-SR total score was significantly correlated with the MADRS total score (r=0.698, p. Conclusions: The QIDS-SR (Chinese version) has good psychometric properties in HBV patients and appears to be useful in assessing depression in clinical settings

Prevalence of internet addiction disorder in Chinese university students: A comprehensive meta-analysis of observational studies

Background and aims: Internet addiction disorder (IAD) is common in university students. A number of studies have examined the prevalence of IAD in Chinese university students, but the results have been inconsistent. This is a meta-analysis of the prevalence of IAD and its associated factors in Chinese university students. Methods: Both English (PubMed, PsycINFO, and Embase) and Chinese (Wan Fang Database and Chinese National Knowledge Infrastructure) databases were systematically and independently searched from their inception until January 16, 2017. Results: Altogether 70 studies covering 122,454 university students were included in the meta-analysis. Using the random-effects model, the pooled overall prevalence of IAD was 11.3% (95% CI: 10.1%–12.5%). When using the 8-item Young Diagnostic Questionnaire, the 10-item modified Young Diagnostic Questionnaire, the 20-item Internet Addiction Test, and the 26-item Chen Internet Addiction Scale, the pooled prevalence of IAD was 8.4% (95% CI: 6.7%–10.4%), 9.3% (95% CI: 7.6%–11.4%), 11.2% (95% CI: 8.8%–14.3%), and 14.0% (95% CI: 10.6%–18.4%), respectively. Subgroup analyses revealed that the pooled prevalence of IAD was significantly associated with the measurement instrument (Q = 9.41, p = .024). Male gender, higher grade, and urban abode were also significantly associated with IAD. The prevalence of IAD was also higher in eastern and central of China than in its northern and western regions (10.7% vs. 8.1%, Q = 4.90, p = .027). Conclusions: IAD is common among Chinese university students. Appropriate strategies for the prevention and treatment of IAD in this population need greater attention

Depressive symptoms in patients with irritable bowel syndrome: A meta-analysis of comparative studies

Depression is common in patients with irritable bowel syndrome (IBS), but the reported prevalence across different studies is inconsistent. This meta-analysis systematically examined the presence and severity of depressive symptoms in patients with IBS. Two investigators independently performed a literature search. The pooled depressive symptom severity was calculated using a random effects model. Subgroup, sensitivity and meta-regression analyses were conducted to examine the moderating factors of the development of depressive symptoms. Twenty four studies (n=2,837) comparing depressive symptoms between IBS patients (n=1,775) and healthy controls (n=1,062) were identified; 14 (58.3%) studies were rated as high quality. Compared to healthy controls, IBS patients had more frequent (OR=9.21, 95%CI: 4.56-18.57, P\u3c0.001; I2=76%) and more severe depressive symptoms (n=1,480, SMD=2.02, 95%CI: 1.56-2.48, P\u3c0.001; I2=94%). Subgroup analyses revealed that patients with all IBS subtypes had more severe depressive symptoms than controls. In addition, versions of the Hamilton Depression Rating Scale (HAM-D) and IBS diagnostic criteria were significantly associated with depressive symptom severity. Meta-regression analyses revealed that female gender, younger age and small sample size were significantly associated with more severe depressive symptoms. In conclusion, meta-analytic data showed that IBS patients had more frequent and severe depressive symptoms than healthy controls. Adequate screening and treatment for depression should be developed and implemented in this patient population

Clinical significance of vasculogenic mimicry in human gliomas

Vasculogenic mimicry (VM) is known as non-endothelial tumor cell-lined microvascular channels in aggressive tumors. We have previously found the presence of VM in high-grade gliomas. In this study, we aimed to identify VM patterns in gliomas and to explore their clinical significance. Tumor samples as well as their detailed clinical/prognostic data were collected from 101 patients. Vasculogenic mimicry in the glioma samples was determined by dual staining for endothelial marker CD34 and periodic acid–Schiff (PAS). Tumor samples were also immunohistochemically stained for Ki-67, VEGF, COX-2 and MMP-9. The association between VM and the clinical characteristics of the patients were analyzed. A Kaplan–Meier survival analysis and log-rank tests were performed to compare survival times of the patients. Vasculogenic mimicry was present in 13 out of 101 samples. The higher grade gliomas had a higher incidence of VM than that of lower grade gliomas (P = 0.006). Vasculogenic mimicry channels were associated with the expression of COX-2 and MMP-9 (P < 0.05). While there was no association between the existence of VM and the sex, age and preoperative epilepsy of the patients, or expression of Ki-67 and VEGF. However, patients with VM-positive gliomas survived a shorter period of time than those with VM negative gliomas (P = 0.027). Interestingly, in high-grade gliomas, the level of microvascular density was lower in VM positive tumors than those VM negative tumors (P = 0.039). Our results suggest that VM channels in gliomas correlate with increasing malignancy and higher aggressiveness, and may provide a complementation to the tumor’s blood supply, especially in less vascularized regions, which may aid in the identification of glioma patients with a poorer prognosis

The association between post-stroke depression, aphasia, and physical independence in stroke patients at 3-month follow-up

Objective: Few studies have examined the association between post-stroke depression (PSD), aphasia, and physical independence in Chinese patients. This study investigated the above association in stroke patients in China at 3-month follow-up. Methods: Altogether 270 patients within 14 days after ischemic stroke were recruited and followed up at 3 months. PSD, aphasia, and physical functional status were measured using the Stroke Aphasia Depression Questionnaire (SADQ), Western Aphasia Battery (WAB), and modified Rankin Scale (mRS), respectively. Patients with mRS total score \u3e2 were considered as having “physical dependence.” Results: Out of 248 patients at 3-month follow up, 119 (48%) were rated as having physical dependence. Multiple logistic regression analyses revealed that female (p = 0.04; OR = 2.2; 95% CI: 1.0–5.1), more severe stroke at admission (p \u3c 0.01; OR = 1.4; 95% CI: 1.3–1.5), and more severe PSD at 3 months (p = 0.01; OR = 1.05; 95% CI: 1.01–1.1) were independently associated with physical dependence at 3 months. Conclusions: Greater PSD and stroke severity were independently associated with physical dependence at 3months after stroke. Aphasia was also associated with physical dependence but the relationship was not significant. Early and effective depression screening, treatment and stroke rehabilitation appear to be important to improve the physical outcome and reduce the burden of stroke survivors