CLEANING AND PREVENTION OF INORGANIC DEPOSITS IN PLATE HEAT EXCHANGERS USING PULSATING CURRENT

Fouling of heat exchangers is a major problem in many industrial processes. The higher temperature of the heat exchange surface compared with the liquid containing precipitable compounds causes the formation of inorganic deposits. Removing the deposits on plate heat exchangers is most often carried out by high-pressure cleaning. This is a laborious task and often increases the corrosion rate of the plates by increasing the roughness of the cleaned surface. This study presents an electrochemical method to clean heat exchange surfaces fouled by deposits and to prevent formation of deposits. This method utilizes pulsating current to polarize heat exchange surfaces with periodic anodic and cathodic DC current. The shape of the pulse and the current density are adjusted to maximize the deposit removal rate, thus minimizing plate corrosion. The optimal pulsating current depends on the material of the heat exchange surface, as well as the composition of the deposits and the solution. For cleaning, the current densities and the frequency of the current pulse are typically higher than those used for preventing deposition. Pulsating current can effectively remove deposits with low solubility, such as TiO2 on titanium heat exchange plates or dense gypsum deposits on stainless steel plates. For cleaning titanium, the cathodic pulse and formation of hydrogen is more essential than in the cleaning of stainless steels. However, the risk of corrosion limits the use of high current densities. Experiments have until now been carried out mainly in the laboratory, though industrial pilot cleaning equipment has also been constructed. An application has already been submitted to patent the method

Prevalencija gena za rezistenciju na meticilin i Panton-Valentine leukocidin u izolatima bakterije Staphylococcus aureus podrijetlom od goveda i ljudi.

Using the California Mastitis Test (CMT), on 46 highly productive dairy farms in Serbia, cows with milk secretion disorder were identified. Milk samples were taken from cows with positive CMT and from cows with clinical mastitis. Standard microbiological analysis of milk samples and API Staph confirmed the presence of 75 isolates of Staphylococcus aureus. Those 75 isolates, as well as 11 isolates of Staphylococcus aureus originating from humans were analyzed for the presence of genes encoding Panton-Valentine leukocidin (PVL) and PBP2A protein, responsible for methicillin resistance. The presence of gene encoding PVL was determined by PCR in 5 out of 75 (6.67%) and in 7 out of 11 (63.63%) bovine and human isolates of Staphylococcus aureus, respectively. The presence of the mecA gene was determined by PCR in 1 of 75 (1.33%) and in 2 of 11 (18.18%) bovine and human isolates of Staphylococcus aureus, respectively. The presence of the mecC gene was not determined in analyzed isolates. Further research is needed to investigate the genetic relationship between bovine and human Staphylococcus aureus isolates, to determine the exact impact of bovine Staphylococcus aureus strains from the cow udders on animal and public health.Uporabom kalifornijskog testa za upalu vimena na 46 visoko produktivnih mliječnih farmi u Srbiji identificirane su krave s poremećajem sekrecije mlijeka. Uzeti su uzorci mlijeka krava pozitivnih kalifornijskim testom i krava s kliničkim mastitisom. Standardnom mikrobiološkom pretragom uzoraka mlijeka i identifikacijom kompletom API Staph potvrđena je prisutnost 75 izolata bakterije Staphylococcus aureus. Tih 75 izolata, kao i 11 izolata te bakterije podrijetlom iz ljudi bili su analizirani lančanom reakcijom polimerazom na prisutnost gena koji kodiraju za Panton-Valentine leukocidin (PVL) i PBP2A protein odgovoran za meticilinsku rezistenciju. Prisutnost gena koji kodira za PVL dokazana je u pet od 75 (6,67%) izolata podrijetlom iz goveda i u sedam od 11 (63,63%) izolata podrijetlom iz ljudi. Prisutnost mecA gena dokazana je u jednog od 75 (1,33%) izolata podrijetlom iz goveda i u dva od 11 (18,18%) podrijetlom iz ljudi. Prisutnost mecC gena nije utvrđena u analiziranim izolatima. Potrebna su daljnja istraživanja kako bi se istražio odnos između izolata Staphylococcus aureus-a podrijetlom iz ljudi i iz goveda i odredio točan utjecaj sojeva vrste Staphylococcus aureus iz vimena krava na zdravlje životinja i zdravlje ljudi

Sea polarisation and the Drell-Hearn-Gerasimov sum-rule(s)

The Drell-Hearn-Gerasimov sum-rule is really two sum-rules: one for each of the valence and the sea/glue contributions to the nucleon wavefunction. The convergence of these sum-rules follows from the Froissart bound for spin dependent processes in QCD and is necessary for the consistency of the constituent quark model of low energy QCD. Some challenges for future polarised photoproduction experiments, for example at ELFE, are discussed.Comment: 10 pages, LaTe

x-Dependent Polarized Parton Distributions

Using QCD motivated and phenomenological considerations, we construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and the overall set can be used to predict polarization asymmetries for various processes. We perform our NLO analysis strictly in x space, avoiding difficulties in moment inversion. Small-x results and other physical considerations are discussed.Comment: 30 pages, 11 Postscript figure

Introduction to the special issue on the statistical mechanics of climate

We introduce the special issue on the Statistical Mechanics of Climate by presenting an informal discussion of some theoretical aspects of climate dynamics that make it a topic of great interest for mathematicians and theoretical physicists. In particular, we briefly discuss its nonequilibrium and multiscale properties, the relationship between natural climate variability and climate change, the different regimes of climate response to perturbations, and critical transitions

High infection rate of zoonotic Eucoleus aerophilus infection in foxes from Serbia.

The respiratory capillariid nematode Eucoleus aerophilus (Creplin, 1839) infects wild and domestic carnivores and, occasionally, humans. Thus far, a dozen of human infections have been published in the literature but it cannot be ruled out that lung capillariosis is underdiagnosed in human medicine. Also, the apparent spreading of E. aerophilus in different geographic areas spurs new studies on the epidemiology of this nematode. After the recognition of the first human case of E. aerophilus infection in Serbia, there is a significant merit in enhancing knowledge on the distribution of the nematode. In the present work the infection rate of pulmonary capillariosis was investigated in 70 red foxes (Vulpes vulpes) from the northern part of Serbia by autopsy. The estimated infection rate with Eucoleus aerophilus was 84%. In contrast, by copromicroscopic examination only 38% of foxes were positive. In addition, 10 foxes were investigated for the closely related species in nasal cavity, Eucoleus boehmi, and nine were positive. Our study demonstrates one of the highest infection rates of pulmonary capillariosis in foxes over the world

Electrical conductivity of milk and bacteriological findings in cows with subclinical mastitis

Intramammary infections change the composition of milk and increase electrical conductivity of milk and decrease milk electrical resistance. Electrical conductivity has been used to detect mastitis during last four decades. The aim of this research was to examine the reliability of the milk electrical conductivity measuring in detection of subclinical mastitis. The experiment was conducted on a dairy farm of Holstein-Friesian breed. A total of 113 quarter milk samples were examined, 55 samples from cows in first stage of lactation and 58 from cows in third stage of lactation. Electrical conductivity (EC) of milk samples was detected by Hand-held EC meter (Draminski mastitis detector). Quarter milk samples for bacteriological analysis were taken aseptically during the morning milking in sterile test tubes. Bacteria growth was not detected in 60 quarter milk samples (53.1%), while in the other 53 samples bacteria was found (46.9%). The most common isolated bacteria in first and third stage of lactation was Corynebacterium spp. (38.9%) and coagulase - negative staphylococci (3.54%). High quality and healthy milk with Draminski mastitis detector was observed in 59.29% of the samples (67/113). Cows with mastitis may not always show an increased EC of milk from the infected quarter. Electrical conductivity of milk can give useful informations about udder health status, but hand-held EC meters, such as Draminski mastitis detector, cannot be used alone in diagnosis of subclinical mastitis