Droplet Evaporation Dynamics of Low Surface Tension Fluids Using the Steady Method.

Droplet evaporation governs many heat- and mass-transfer processes germane in nature and industry. In the past 3 centuries, transient techniques have been developed to characterize the evaporation of sessile droplets. These methods have difficulty in reconciling transient effects induced by the droplet shape and size changes during evaporation. Furthermore, investigation of evaporation of microdroplets residing on wetting substrates, or fluids having low surface tensions (<30 mN/m), is difficult to perform using established approaches. Here, we use the steady method to study the microdroplet evaporation dynamics of low surface tension liquids. We start by employing the steady method to benchmark with water droplets having base radii (20 ≤ Rb ≤ 260 µm), apparent advancing contact angle (45° ≤ θa,app ≤ 162°), surface temperature (30 < Ts < 60 °C), and relative humidity (40% < ϕ < 60%). Following validation, evaporation of ethanol (≈22 mN/m), hexane (≈18 mN/m), and dodecane (≈25 mN/m) were studied for 90 ≤ Rb ≤ 400 µm and 10 < Ts < 25 °C. We elucidate the mechanisms governing the observed behavior using heat and mass transport scaling analysis during evaporation, demonstrating our steady technique to be particularly advantageous for microdroplets, where Marangoni and buoyant forces are negligible. Our work not only elucidates the droplet evaporation mechanisms of low surface tension liquids but also demonstrates the steady method as a means to study phase change processes.

Optically Transparent Thermally Insulating Silica Aerogels for Solar Thermal Insulation.

Rooftop solar thermal collectors have the potential to meet residential heating demands if deployed efficiently at low solar irradiance (i.e., 1 sun). The efficiency of solar thermal collectors depends on their ability to absorb incoming solar energy and minimize thermal losses. Most techniques utilize a vacuum gap between the solar absorber and the surroundings to eliminate conduction and convection losses, in combination with surface coatings to minimize reradiation losses. Here, we present an alternative approach that operates at atmospheric pressure with simple, black, absorbing surfaces. Silica based aerogels coated on black surfaces have the potential to act as simple and inexpensive solar thermal collectors because of their high transmission to solar radiation and low transmission to thermal radiation. To demonstrate their heat-trapping properties, we fabricated tetramethyl orthosilicate-based silica aerogels. A hydrophilic aerogel with a thickness of 1 cm exhibited a solar-averaged transmission of 76% and thermally averaged transmission of ≈1% (at 100 °C). To minimize unwanted solar absorption by O-H groups, we functionalized the aerogel to be hydrophobic, resulting in a solar-averaged transmission of 88%. To provide a deeper understanding of the link between aerogel properties and overall efficiency, we developed a coupled radiative-conductive heat transfer model and used it to predict solar thermal performance. Instantaneous solar thermal efficiencies approaching 55% at 1 sun and 80 °C were predicted. This study sheds light on the applicability of silica aerogels on black coatings for solar thermal collectors and offers design priorities for next-generation solar thermal aerogels.

Steady Method for the Analysis of Evaporation Dynamics.

Droplet evaporation is an important phenomenon governing many man-made and natural processes. Characterizing the rate of evaporation with high accuracy has attracted the attention of numerous scientists over the past century. Traditionally, researchers have studied evaporation by observing the change in the droplet size in a given time interval. However, the transient nature coupled with the significant mass-transfer-governed gas dynamics occurring at the droplet three-phase contact line makes the classical method crude. Furthermore, the intricate balance played by the internal and external flows, evaporation kinetics, thermocapillarity, binary-mixture dynamics, curvature, and moving contact lines makes the decoupling of these processes impossible with classical transient methods. Here, we present a method to measure the rate of evaporation of spatially and temporally steady droplets. By utilizing a piezoelectric dispenser to feed microscale droplets (R ≈ 9 µm) to a larger evaporating droplet at a prescribed frequency, we can both create variable-sized droplets on any surface and study their evaporation rate by modulating the piezoelectric droplet addition frequency. Using our steady technique, we studied water evaporation of droplets having base radii ranging from 20 to 250 µm on surfaces of different functionalities (45° ≤ θa,app ≤ 162°, where θa,app is the apparent advancing contact angle). We benchmarked our technique with the classical unsteady method, showing an improvement of 140% in evaporation rate measurement accuracy. Our work not only characterizes the evaporation dynamics on functional surfaces but also provides an experimental platform to finally enable the decoupling of the complex physics governing the ubiquitous droplet evaporation process.

Non-directed, carbonate-mediated C-H activation and aerobic C-H oxygenation with Cp*Ir catalysts.

The effect of oxidatively stable L- and X-type additives on the activity of Cp*Ir catalyst precursors in the C-H activation of arenes has been studied. Turnover numbers for C-H activation of up to 65 can thus be achieved, as determined by H/D exchange in MeOH-D4. In particular, carbonate additives are found to enhance the C-H activation reactivity of Cp*Ir(H2O)3(OTf)2 () more significantly than L-type ligands investigated in this study. Based on these studies, Cp*Ir/carbonate systems are developed that catalyze the aerobic Csp(3)-H oxygenation of alkyl arenes, employing air as oxidant.

A case of Beckwith-Wiedemann syndrome with peculiar dental findings.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS, OMIM 130650) is a rare genetic disorder characterised by overgrowth, tumor predisposition and congenital malformations. Few systemic manifestations and oral features have been reported so far. CASE REPORT: We report on a case of BWS, describing all features expanding the knowledge on oro-dento-facial phenotypes, along with a review of the literature.

Influence of caffeic acid phenethyl ester on bone healing in a rat model.

OBJECTIVE: To examine the effects of caffeic acid phenethyl ester (CAPE; a component of honey bee-hive propolis with antioxidant, anti-inflammatory, antiviral and anticancer properties) on bone regeneration and fibrotic healing in a rat model. METHODS: Male Sprague-Dawley rats (n = 63; mean age 7 weeks; weight 280-490 g) were randomly divided into three groups: A, cranial defect with no bone healing treatment (n = 21); B, cranial defect treated with CAPE (n = 21); C, cranial defect treated with CAPE and ß-tricalcium phosphate/hydroxyl apatite (n = 21). Rats were anaesthetized with ketamine (8 mg/100 g) by intraperitoneal injection and a cranial critical size bone defect was created. Following surgery, CAPE (10 µmol/kg) was administered by daily intraperitoneal injection. Seven rats in each group were killed at days 7, 15 and 30 following surgery. Bone regeneration, fibrotic healing and osteoblast activity were evaluated by histopathology. RESULTS: Statistically significant differences in healing were found between all groups. There were no statistically significant within-group differences between day 7 and 15. At day 30, bone healing scores were significantly higher in groups B and C compared with group A. CONCLUSION: CAPE significantly improved bone-defect healing in a rat model, suggesting that CAPE has beneficial effects on bone healing.

The reliability of microleakage studies using dog and bovine primary teeth instead of human primary teeth.

AIM: This was to investigate if dental restorations on human, dog and bovine primary teeth are equitable for microleakage analysis, and the respective marginal adaptation deficiency in in vitro conditions. MATERIALS AND METHODS: In order to determine the level of microleakage in Class V poly acid-modified composite restorations of human, dog and bovine primary teeth, samples were evaluated by dye-leakage method in sections of the inner area of the restorations. RESULTS: We found no leakage in 6 out of 10 (60%) human restorations, in 7 out of 10 (70%) of dog and in 7 out of 10 (70%) of bovine teeth. The levels of dye-microleakage were tested with Kruskal-Wallis one-way variant analysis method. The relative leakage differences were not statistically significant among all species (p>0.05). CONCLUSION: We concluded that dog and bovine primary teeth might be suitable for in vitro studies instead of human ones.

Can exposure to manganese and extremely low frequency magnetic fields affect some important elements in the rat teeth?

BACKGROUND: Length and level of exposure to electromagnetic fields (EMFs) is increasing in association with the widespread use of electrical and electronic devices and technological progress. The undesirable effects of extremely low frequency magnetic fields (ELF-MFs) on health have attracted considerable interest. MATERIALS AND METHODS: Sixty-four four-month-old male Wistar rats divided into eight groups of eight rats each were used. Seven groups were exposed to varying dosages of manganese (Mn) and a 50 Hz magnetic field (MF) of approximately 1 mT, while the last group was set aside as the cage control group and not subjected to any procedure. This study was intended to investigate the interactions between the application of MF and Mn and the elements Ca, Zn, Mg, and P thought to be involved in caries, in rat teeth. RESULTS: Levels of Ca, Mg, Zn, and P in the experimental group rats were different to those in the control group. CONCLUSIONS: The results demonstrate that ELF-MF and Mn can have significant effects on levels of elements in rat teeth. Further experimental and epidemiological studies of ELF-MF and Mn are needed in order to evaluate their dental effects.

Phosphodiesterase-5 inhibitors may facilitate bone defect recovery.

BACKGROUND AND OBJECTIVES: Bone healing is still one of the most important problems of the oral and maxillofacial surgery procedures. This study was designed to evaluate the effect of sildenafil citrate (which is used for erectile dysfunction) on bone defect healing in an experimental animal model. MATERIALS AND METHODS: A total of 42 male Wistar-albino rats were randomly assigned to the control group (n=21) or the study group (n=21). The control group was fed on a standard laboratory diet until 12 h before surgery, whereas the study group received Sildenafil citrate via orogastric tube 10 mg/kg once a day for 30 days. Under anaesthesia, a 3 x 3 x 2 mm depth defect was made on tibia of each rat. 7 animals from each group were euthanised on postoperative days 7,15 and 30. Bone samples were taken for examination, histologically on day 7, by 3D dental tomography on day 15, and for bone strength resistance on day 30. RESULTS: Statistically significant differences were determined between the groups from the inflammatory and repair phase, with the healing process being more advanced in the Sildenafil group. CONCLUSIONS: Sildenafil citrate can be used as a supporting factor to accelerate the healing process of bone. In future comprehensive studies will need to demonstrate the Sildenafil citrate affect on bone defect healing.

Bruxism: is it a new sign of the cardiovascular diseases?

AIM: To determine the relationship between bruxism and cardiovascular diseases. MATERIALS AND METHODS: 120 patients who referred to the Dentistry Faculty with the complaint of bruxism were selected. All patients gave informed consent for participation in the study. All of the patients were examined and bruxism was classified. And also these were examined by B-mode ultrasound to measure the Intima Media Thickness (IMT) at the far wall of the common carotid artery. A wide range of vascular risk factors including age, gender, body mass index, and previous history were surveyed. Spearman correlation analysis was performed to ascertain quantitative comparison, Mann-Whitney U and Kruskal-Wallis test were used for comparison of means RESULTS: There were 66 (55%) male and 54 (45%) female patients, with a female to male ratio of 1/1.2. The mean age was 35.6 +/- 1,25 years (range 18-65 years). In the analysis of bruxism classification and IMT there was a statistical significance between bruxism classification subgroup 1, 2, 3 and IMT. There was no statistical significance between bruxism classification Subgroup 4 and IMT due to the small number of the patients (n = 12). CONCLUSIONS: Stressful situations can cause both bruxism and cardiovascular disease such as coronary artery diseases, hypertension, arrhythmias, cardiomyopathy. The statistical analysis supported this hypothesis. However, we need to new studies with large number of samples to confirm this hypothesis. Clearly, future studies in this field will need to take into consideration the influence of the following variables: age, use of medication or drugs, smoking habits, and other sleep disorders.

Co-composting kinetics of rose processing waste with OFMSW.

The objective of this study was to evaluate the kinetics of co-composting of rose processing waste (RPW) and organic fraction of municipal solid waste (OFMSW). Experimental data was obtained from 65-L batch reactors. Mixtures settled up with different ratios of RPW, OFMSW, inoculation, and bulking agent. The data was consisting of CO(2) evolution and inner temperature changing with time in the reactors. Decomposition process was evaluated based on rapidly and slowly biodegradable fractions of organic matter. The experimental data has been analyzed by kinetic models including the first-zero-order, first-first-order, Chen and Hashimoto's and Levi-Minzi's kinetic models using non-linear regression techniques. Kinetic parameters and rate constants were evaluated based on the average relative errors and coefficient of determination. The results of study showed that the best fitting kinetic model is the first-first-order.

Does eradication of Helicobacter pylori reduce hypergastrinaemia during long term therapy with proton pump inhibitors?

OBJECTIVES: To evaluate the effect of Helicobacter pylori (Hp) eradication therapy on blood gastrin levels in long-term PPI users, since proton pump inhibitors (PPIs) and Helicobacter pylori (Hp) are major causes of hypergastrinaemia. DESIGN: A prospective study. SUBJECTS: Twenty seven Hp (+) patients enrolled in the study. Twenty were given eradication treatment (ET group), and the rest were given symptomatic treatment (ST group). Those who remained Hp (+) after eradication therapy were also added into the ST group. Lansoprazol 30 mg/day was given to both groups for three months thereafter. RESULTS: Fasting and non-fasting blood gastrin levels (FGL and NFGL) were measured initially and one month and four months after treatment. At the end of fourth month, FGL was significantly higher than both initial and first month level (p < 0.01) in the ST group. NFGL in this group did not change significantly (p > 0.05) after eradication therapy. In the ET group, FGL was significantly higher in the fourth month than the first month (p < 0.001) and than the initial level (p < 0.05). NFGL was higher, but not statistically in the fourth month than in the first month (p > 0.05) and significantly lower than the initial level (p < 0.05) in this group. CONCLUSION: We suggest that testing for Hp positivity and treating it if detected would be an appropriate approach to avoid hypergastrinaemia, especially in candidate patients for long term PPI treatment.

Seropositivity against Helicobacter pylori CagA in Turkish gastric cancer patients.

BACKGROUND: Increased prevalence of CagA in gastric cancer has been reported; yet, other reports suggest that the cagA gene is not associated with gastric cancer. GOALS: To evaluate the frequency of CagA seropositivity in Turkish patients with gastric cancer. STUDY: Thirty-two patients with gastric adenocarcinoma and 46 patients with nonulcer dyspepsia were examined for Helicobacter pylori status and for antibodies against CagA. RESULTS: H. pylori was positive in 56.3% of patients and in 71.7% of controls. CagA was positive in all patients in the study group, regardless of H. pylori positivity, and in 56.5% of the control group. CagA positivity in H. pylori -positive patients was significantly more frequent in patients with gastric cancer than in those with nonulcer dyspepsia ( p < 0.001). As for H. pylori -negative patients in both groups, CagA positivity was also more frequent in gastric cancer patients ( p < 0.001). CONCLUSION: Testing for H. pylori antibodies without testing for antibodies against CagA will miss patients with either recent or previous infection, which may be a cause of missing the relationship between H. pylori and gastric cancer. The authors think that testing for CagA in patients with dyspepsia can reveal which patients should be followed up for the risk of developing gastric cancer.

Activated Protein C Resistance in Polycythemia Vera.

Activated protein C resistance is a result of a point mutation in factor V gene (Leiden mutation) and can be identified in approximately 50% of patients with thrombosis, making it an important risk factor for thrombosis. The aim of this study is to evaluate the role activated protein C resistance in the hypercoagulable state seen in polycythemia vera. We compared patients with polycythemia vera (n: 24) for increased risk of thromboembolism and activated protein C resistance, with the results of patients with chronic myelogenous leukemia (n: 27) and healthy control group (n: 52). Activated protein C resistance test and factor VIII activity was determined by an aPTT based test. Anticardiolipin antibodies IgG and IgM were also determined by ELISA. Leiden mutation was studied with polymerase chain reaction. Venous thromboses were observed in 12.5% and arterial thromboses in 41.6% of patients with polycythemia vera. Arterial thromboses were recognized in 7.4% of patients with chronic myelogenous leukemia. Activated protein C resistance was identified in 20.8% of patients with polycythemia vera and 14.8% with chronic myelogenous leukemia (versus 1.8% of healthy control subjects). The risk of thrombosis in patients with polycythemia vera was independent from the presence of activated protein C resistance. Leiden mutation was observed in only 1 patient out of 4 patients with chronic myelogenous leukemia who had activated protein C resistance, but not thrombosis. Factor VIII levels of patients with chronic myelogenous leukemia (158% ± 14) were higher than healthy control subjects (99% ± 15) (p< 0.05). Patients with activated protein C resistance in both groups had no seropositivity for anticardiolipin antibodies IgG and IgM. Activated protein C resistance and in some cases its association with Leiden mutation in polycythemia vera may not have a major role in the pathogenesis of thromboembolic complications of polycythemia vera.

Familial Mediterranean fever. A review of the disease and clinical and laboratory findings in 105 patients.

BACKGROUND: The diagnosis of familial Mediterranean fever still remains clinical, since no specific laboratory test exists, other than a molecular genetic test which is not widely available. AIM: To evaluate the clinical findings in 105 Turkish patients; to compare these findings with those in the literature; and to make a brief review of the disease. METHODS: A total of 105 familial Mediterranean fever patients were evaluated either retrospectively (for those diagnosed before 1997), or prospectively (for those after 1997). A diagnostic criteria set was used in addition to the clinical and laboratory findings that can be seen in familial Mediterranean fever, including the newly described manifestations. Previously selected clinical and laboratory parameters were observed for three consecutive days. RESULTS: Of our patients, 88.5% were of Turkish, 3.8% of Armenian and 7. 6% of Jewish origin. Family history was positive in 87 (82.8%) patients. Involved site was peritoneum in 97 (92%), joints in 45 (42.8%) and pleura in 19 (18%). Frequency of myalgia/arthralgia was 24.7%, and skin findings were observed in 16. 1% of patients. Splenomegaly, not related to amyloidosis, was present in 21 (20%) patients. Meningeal, retinal or ovarian/testicular involvement was not observed. CONCLUSION: Identification of familial Mediterranean fever gene has led to the application of a molecular genetic test for the diagnosis of Familial Mediterranean Fever. Until genetic methods become widely available, diagnosis will remain clinical. Thus, awareness of various clinical forms and of the correct usage of diagnostic criteria in various patient populations is important.

Skin hyperreactivity of Behçet's patients (pathergy reaction) is also positive in interferon alpha-treated chronic myeloid leukaemia patients, indicating similarly altered neutrophil functions in both disorders.

Typical manifestations of Behcet's disease (BD) and a positive pathergy reaction were observed in a few patients with chronic myeloid leukaemia (CML) on interferon alpha (IFN-alpha) therapy and the significance of this observation was assessed in a prospective study. The skin pathergy test was applied to 15 patients with CML prior to IFN-alpha therapy, 29 patients with CML following IFN-alpha therapy and 30 patients with BD. Twenty-five patients with inflammatory arthropathies (IA), 20 patients with recurrent oral ulcers (ROU), 23 patients treated with IFN-alpha for various disorders and 20 normal individuals were also studied as control groups. The pathergy reaction was positive in nearly a quarter of IFN-alpha-treated CML cases (24%) as well as one-half of the patients with BD (50%). All CML patients prior to IFN-alpha treatment and all patients using IFN-alpha for other diseases were negative for the pathergy reaction. These results may indicate a similarly altered neutrophil function in both BD and IFN-alpha-treated CML patients.

Therapeutic efficacy of recombinant interferon-alpha in polycythaemia vera.

The therapeutic efficacy of recombinant interferon-alpha (rIFN-alpha) has been evaluated in 7 patients with polycythaemia vera (PV), diagnosed according to the criteria of the Polycythemia Vera Study Group. Six complete responses and one partial response were achieved. Pruritus significantly improved in 80% (4/5) of the cases. Recombinant interferon-alpha had to be discontinued in 1 patient because of grade 3-4 nephrotoxicity according to WHO criteria. rIFN-alpha therapy significantly decreased the phlebotomy requirements and improved the mean corpuscular volume, erythrocyte and platelet counts, pruritus complaints and the degree of splenomegaly (p < 0.05). rIFN-alpha seems to be an effective treatment modality for the myeloproliferation of PV and pruritus complaints.

Sample adequacy in detecting Chlamydia trachomatis.

OBJECTIVE: Chlamydia trachomatis is an important etiological agent in female genital infection and may result in infertility. In recent years rapid diagnostic methods have become widely used as alternatives to cell culture. Our objective was to evaluate the technique of direct fluorescence assay (DFA) in estimating the presence of C. trachomatis. METHODS: Specimens taken from 40 infertile and 20 fertile women were examined by DFA for the presence of C. trachomatis. RESULTS: Six of forty (15%) infertile women were found to be positive whereas no positive specimens were detected in the control group. When the specimens were grouped into those which were adequate or inadequate, 19 and five specimens, respectively, were adequate in the infertile and healthy groups. If only adequate specimens are included in estimating the presence of Chlamydia, the percentage is 31.6%. CONCLUSIONS: In order to use DFA as a more reliable and rapid diagnostic test of C. trachomatis in female genital infection, false-negativity must be eliminated. Specimens must be collected adequately and concentrated in order to achieve optimal diagnostic success.

Seroprevalence of rubella virus in Turkish pregnant women.

OBJECTIVES: To assess the immune status of a group of Turkish pregnant women who had never been immunized. METHODS: Between June 1990 and April 1993, the seroprevelance of rubella was determined in the study group of 1351 women. RESULTS: A total of 242 (17.9%) pregnant women were found to be susceptible to rubella infection and the seropositivity rate related to prior infection was 82.1%. CONCLUSIONS: The importance of Rubella IgG determination in Turkish pregnant women is discussed and recommendations for prevention and control of congenital rubella syndrome (CRS) are suggested.

Plant regeneration from cultured hypocotyl explants of diploid and tetraploid Solanum khasianum clarke.

Plant regeneration through shoot bud formation was induced in cultured hypocotyl explants of diploid and tetraploid varieties of Solanum khasianum. Optimum regeneration of multiple shoot buds accompanied by rooting occurred on Murashige and Skoog's medium supplemented with IAA (1 mg/1) and kinetin or benzyladenine (1 mg/1). Plantlets obtained in vitro were successfully established in soil.