Heat transfer investigation of compressed-water absorbed snow spheres

Yaz aylarında dağlarda bulunabilecek karın soğutma amacıyla kullanılabilmesi için borular vasıtası ile taşınması mümkündür. Ancak karın, bulunduğu formda veya su ile salamura şeklinde taşınması sıkıntılıdır. Dirsek gibi akışın yön değiştirdiği yerlerde karın boruları tıkaması ve dağda sahip olduğu soğu enerjisini daha kolay kaybetmesi gibi problemler vardır. Bu nedenle karın sıkıştırılıp su emdirildikten sonra soğutularak buzlaştırılması düşünülmüştür. Bu sayede kar küre, boru içerisinde hareket ederken dışarıdan içeriye doğru eriyeceği için kolaylıkla parçalanmayacak ve salamura oluşmayacaktır. Bu çalışma kapsamında sıkıştırılarak küresel hale getirilen karın, önce sıfır dereceye getirilmesi, sıfır derecede su emdirilmesi ve son olarak da soğutularak buzlaştırılması prosesi ele alınmıştır. Soğutma hem doğal taşınım ile hem de zorlanmış taşınım ile yapılmıştır. Oluşturulan deney sistemi ile sıkıştırılarak yarım küre haline getirilmiş karın su emdirildikten sonra soğutularak buzlaştırılması süresince gerçekleşen ısı transferi deneysel olarak incelenmiştir. Kar, geliştirilen sıkıştırma aparatı ile 80 mm çapında yarım kürelere dönüştürülmüştür. Farklı yoğunluklarda yarım küreler elde edilerek farklı gözeneklilikler elde edilmiştir. Bu yarım küreler daha sonra sıfır dereceye getirilmiş ve sonrasında da sıfır derecedeki suya daldırılarak su emmeleri sağlanmıştır. Deneyler yorumlanırken kar kürelerin homojen gözeneklilikte olduğu ve homojen su emdikleri kabulü yapılmıştır. Yapılan deneysel çalışma sonucunda farklı gözenekliliklerdeki kar kürelerin soğuma süresince iç bölgelerindeki sıcaklık dağılımları, buzlaşmanın zamana göre değişimi oluşturulan eğrilerle verilmiştir. Deneysel çalışmalarda gözeneklilik azaldıkça su emmenin azaldığı, yoğunluğu 0.82 g/cm3’ten büyük olan numunelerin ise su emmediği gözlemlenmiştir. Anahtar Kelimeler: Kar, buz, faz değişimi, ısı transferi.It is possible to use the natural snow accumulated on mountains for the aim of refrigeration when needed, especially in summer times. Making ice spheres from snow is suggested for transferring this accumulated snow from mountains to the places where refrigeration is needed. In this study, ice-sphere making process and heat and mass transfer mechanisms during this icing process are investigated experimentally. Today, transferring of ice for long distances is realized in the mixture form of snow and water. The most important disadvantage of transferring of snow mixture in pipe lines is the blockage of the flow because of accumulation of the snow in the elbows which is the place of flow direction changes. Another important disadvantage is large pressure losses. To overcome all these problems ice-spheres are being suggested. In this study, firstly making snow balls by compression, and then, saturating them with water and lastly, getting ice ball by cooling is aimed. To prevent the blockage of the balls in the pipeline's elbows, the diameter of the balls should be chosen bigger than the radius of the pipe. Otherwise, we will meet a flow characteristic called slush flow in the literature. In this study, the aimed flow is known as plug flow. In the literature, the plug flow of the plastic balls examined by Ulusarslan (2003) experimentally. In the mentioned study, the plug flow of the plastic balls was investigated and pressure losses of the flow determined experimentally. In addition, plug and slug flow are compared with each other. According to the study in the plug flow;  Pressure losses are less. There is no blockage risk. It is possible to carry more mass. Less power is required to carry. During the transfer of the balls in the pipelines, icing of the snow balls has to be done to prevent breaking into pieces. The icing process is done by compression of the snow into the form of sphere and saturating it with water. Water can be used as a binder. The most important think here is how much water should be used in the penetration process. The excess water causes the balls breaking into pieces. On the other hand, the less water amount causes insufficient binding of the snow granules. By compression of the balls, the air gaps inside the snow balls are decreased. Thus the density of the snow increases depending on the compaction level. At the end, the bonds between snow granules will be stronger. Compaction level, compaction velocity and temperature are very important parameters affecting the process. It is very important to determine correctly which values of the parameters should be used to have enough strength of the snow ball during the transfer process. The experimental studies have been carried out to get correct values and to investigate the heat and mass transfer characteristics of the snow. The following experimental results have been obtained; It is possible to produce strengthened ice balls by cooling the snow ball after compression of snow into the form of sphere and saturating it with water. After compression step, since close cellular structure is gained, the snow ball can't absorb any amount of water if the density of the snow ball is greater than 0.82 g/cm3. Experimental results in various conditions have been compared. The same trend-lines have been obtained for the same conditions. The differences between forced convection and natural convection cooling processes have been determined for the samples absorbing same amount of water. In natural convection cooling process, the total icing time is about 4 hour. However, in forced convection, it is about 1 hour. Absorbed water amount increases with the cooling time. During the cooling process, the temperature vs time profile of all the samples have been determined experimentally and all these results are given in the form of graphs in this study for various spheres having different porosities. Keywords: Snow, ice, phase change, heat transfer

H2S biosynthesis and catabolism: new insights from molecular studies

Hydrogen sulfide (H2S) has profound biological effects within living organisms and is now increasingly being considered alongside other gaseous signalling molecules, such as nitric oxide (NO) and carbon monoxide (CO). Conventional use of pharmacological and molecular approaches has spawned a rapidly growing research field that has identified H2S as playing a functional role in cell-signalling and post-translational modifications. Recently, a number of laboratories have reported the use of siRNA methodologies and genetic mouse models to mimic the loss of function of genes involved in the biosynthesis and degradation of H2S within tissues. Studies utilising these systems are revealing new insights into the biology of H2S within the cardiovascular system, inflammatory disease, and in cell signalling. In light of this work, the current review will describe recent advances in H2S research made possible by the use of molecular approaches and genetic mouse models with perturbed capacities to generate or detoxify physiological levels of H2S gas within tissue

Resolution of inflammation: a new therapeutic frontier

Dysregulated inflammation is a central pathological process in diverse disease states. Traditionally, therapeutic approaches have sought to modulate the pro- or anti-inflammatory limbs of inflammation, with mixed success. However, insight into the pathways by which inflammation is resolved has highlighted novel opportunities to pharmacologically manipulate these processes — a strategy that might represent a complementary (and perhaps even superior) therapeutic approach. This Review discusses the state of the art in the biology of resolution of inflammation, highlighting the opportunities and challenges for translational research in this field

Ventricular tachyarrhythmia during pregnancy in women with heart disease: Data from the ROPAC, a registry from the European Society of Cardiology

Objectives: To describe the incidence, onset, predictors and outcome of ventricular tachyarrhythmia (VTA) in pregnant women with heart disease. Background: VTA during pregnancy will cause maternal morbidity and even mortality and will have impact on fetal outcome. Insufficient data exist on the incidence and outcome of VTA in pregnancy. Methods and results: From January 2007 up to October 2013, 99 hospitals in 39 countries enrolled 2966 pregnancies in women with structural heart disease. Forty-two women (1.4%) developed clinically relevant VTA during pregnancy, which occurred mainly in the third trimester (48%). NYHA class > 1 before pregnancy was an independent predictor for VTA. Heart failure during pregnancy was more common in women with VTA than in women without VTA (24% vs. 12%, p = 0.03) and maternal mortality was respectively 2.4% and 0.3% (p = 0.15). More women with VTA delivered by Cesarean section than women without VTA (68% vs. 47%, p = 0.01). Neonatal death, preterm birth (< 37 weeks), low birthweight (< 2500 g) and Apgar score < 7 occurred more often in women with VTA (4.8% vs. 0.3%, p = 0.01; 36% vs. 16%, p = 0.001; 33% vs. 15%, p = 0.001 and 25% vs. 7.3%, p = 0.001, respectively). Conclusions: VTA occurred in 1.4% of pregnant women with cardiovascular disease, mainly in the third trimester, and was associated with heart failure during pregnancy. NYHA class before pregnancy was predictive. VTA during pregnancy had clear impact on fetal outcome

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P &lt; 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Profound Chemopreventative Effects of a Hydrogen Sulfide-Releasing NSAID in the APC(Min/+) Mouse Model of Intestinal Tumorigenesis

Canadian Institutes of Health Research grant to JL

Risk of diabetes after para-aortic radiation for testicular cancer

Background: While the risk of diabetes is increased following radiation exposure to the pancreas among childhood cancer survivors, its association among testicular cancer (TC) survivors has not been investigated. Methods: Diabetes risk was studied in 2998 1-year TC survivors treated before 50 years of age with orchidectomy with/without radiotherapy between 1976 and 2007. Diabetes incidence was compared with general population rates. Treatment-specific risk of diabetes was assessed using a case–cohort design. Results: With a median follow-up of 13.4 years, 161 TC survivors were diagnosed with diabetes. Diabetes risk was not increased compared to general population rates (standardised incidence ratios (SIR): 0.9; 95% confidence interval (95% CI): 0.7–1.1). Adjusted for age, para-aortic radiotherapy was associated with a 1.66-fold (95% CI: 1.05–2.62) increased diabetes risk compared to no radiotherapy. The excess hazard increased with 0.31 with every 10 Gy increase in the prescribed radiation dose (95% CI: 0.11–0.51, P = 0.003, adjusted for age and BMI); restricted to irradiated patients the excess hazard increased with 0.33 (95% CI: −0.14 to 0.81, P = 0.169) with every 10 Gy increase in radiation dose. Conclusion: Compared to surgery only, para-aortic irradiation is associated with increased diabetes risk among TC survivors