Search

Purpose Patients with WPW syndrome have an increased mortality rate compared to the general population. Although asymptomatic preexcitation has previously been considered benign, recent studies have found that also asymptomatic patients have clinical and electrophysiological factors associated with increased risk of sudden cardiac death. This study compares the baseline electrophysiological characteristics of accessory pathways in symptomatic and asymptomatic patients with preexcitation. We hypothesized that a significant proportion of asymptomatic patients has inducible orthodromic tachycardia during programmed electrical stimulation. Methods This retrospective study includes 1853 patients with preexcitation who underwent invasive electrophysiological testing in two Swedish University Hospitals between 1991 and 2018. The mean age was 36 ± 17 years with a range of 3–89 years. Thirty-nine percent was women. A total of 269 patients (15%) were children younger than 18 years. Electrophysiological data included effective refractory period of the accessory pathway (APERP, in 1069 patients), tachycardia cycle length, inducibility and type of tachycardia, and AP localization. Results A total of 1703 (93%) patients reported symptoms suggesting tachyarrhythmias before the study and 128 (7%) were asymptomatic. The proportion of potentially dangerous pathways with short APERP (≤ 250 ms) were similar in symptomatic and asymptomatic patients (187/949, 20% vs. 25/108, 23%) (P = 0.40) as was the mean APERP (303 ± 68 ms vs. 307 ± 75) (P = 0.61). The proportion of patients who had inducible arrhythmia was larger in the symptomatic group (64% vs. 31%) (P Conclusion The results of this study strengthen the present guideline recommendation (IIA) to consider invasive risk assessment in patients with asymptomatic preexcitation.

Operations research can be used to apply analytical methods that help make precise and reasonable decisions. In road maintenance, basic principles of operations research are used to create model formulation that could help lower costs in case of an inaccurately made decision. First, the paper provides a literature review on different model formulations. Afterward, hypotheses are proposed regarding the model formulation, and then the model that minimises total generalised costs from wrong duty orders for road maintenance is offered. In conclusion, the paper evaluates the hypotheses and the process of improving the mathematical model.

The presence of excess water in centralized sewerage systems is known to have a multitude of unfavorable effects on the daily operation of the wastewater infrastructure. The additional volume of I/I-water decreases the hydraulic capacity of wastewater collection networks, reduces the efficiency of wastewater treatment processes, and increases the costs of transporting and treating the wastewater. Currently, most I/I studies in Latvia are conducted on the scale of the wastewater treatment plant service area and determine only the common performance indicators for a given year. However, data of such resolution are not sufficient to identify problem areas within the networks and to introduce cost-effective measures. The contribution of private sewer laterals to the overall I/I volume is an area of particular interest. Although it is possible to locate and quantify I/I from individual house connections, in practice, given the financial and time constraints, it is not feasible to apply a case-by-case approach. Thus, a simple method to predetermine the problematic parts of the system before conducting on-site inspections is needed. This study investigates the link between groundwater levels and observed night-time wastewater flows on a sub-catchment scale by performing a linear regression analysis (940 data points in total). The results show a direct correlation (R > 0.70 in all cases) between said parameters and highlight the impacts of poorly built and ill-maintained house connections. The presented approach can be widely adopted by system operators to help identify potential sources of diluted wastewater and to aid in the development of priority-based renovation plans.

Hydrolysis of the lignocellulosic biomass results in the release of high-value chemicals that during industrial processing can be recovered with membrane technologies. To maintain an effective performance of the membranes used in the technological processing of biomass, their regular cleaning is essential. Although several guidelines may be found for membrane cleaning in the cases of organic fouling, the data for cleaning membranes fouled by hydrolyzed lignocellulosic biomass is limited. Current research is aimed to evaluate physical (air backpulse) and common cheap chemical membrane cleaning methods. The results showed that air backpulse alone had a minor (9%) effect on the membrane cleaning. The alternation of NaOH (1 %) solution with the NaClO (200 mg/L of Free chlorine) was the most effective approach for membrane cleaning. The cleaning effectiveness was 95.1 % for 50 nm membrane and 89 % for 200 nm membrane, indicating that membranes used for hydrolyzed lignocellulosic biomass filtration can be effectively cleaned using affordable and accessible chemicals.

Highlights • Assessing the relationship between atrial fibrillation and quality of life. • Implantable loop recorders assessed rhythm continuously in symptomatic patients. • Atrial fibrillation burden, episode duration and frequency were included. • Higher atrial fibrillation burden was associated with impaired quality of life., Aims To assess the relation between atrial fibrillation (AF) characteristics and health-related quality of life (QoL), and which AF characteristic had the greatest impact. Method The AF characteristics burden (percentage of time in AF), duration and number of AF episodes/month were obtained from implantable cardiac monitors during the 2-month run-in period in 150 patients included in the randomized CAPTAF trial comparing early ablation and antiarrhythmic drug therapy. The QoL was measured by the General Health and Vitality dimensions of the 36-Item Short-Form Health Survey. AF characteristics were analysed continuously and in quartiles (Q1-Q4). Results Greater AF burden (p = 0.003) and longer AF episodes (p = 0.013) were associated with impaired QoL (Vitality score only) in simple linear regression analyses. Greater AF burden was, however, the only AF characteristic associated with lower QoL, when adjusted for sex, type of AF, hypertension, heart rate above 110 beats per minute during AF, and beta-blocker use in multiple linear regression analyses. For every 10% increase in AF burden there was a 1.34-point decrease of Vitality score (95% confidence interval (CI) −2.67 to −0.02, p = 0.047). The Vitality score was 12 points lower (95% CI −22.73 to −1.27, p = 0.03) in patients with an AF burden > 33% (Q4) versus those with

Biogas is a common source of renewable energy. But biogas plants also produce a by-product which is at least as valuable as renewable energy, because of its nutrients and organic matter content – digestate. Digestate is an excellent fertilizer containing many different nutrients and micronutrients necessary for agriculture, including nitrogen, phosphorus and potassium. Digestate can be characterized based on the feedstock used to produce biogas. Latvia’s biogas plants produce digestate from: manure and agricultural sludge (85 %), sewage sludge (5 %) and municipal waste (10 %). However, digestate misuse can cause a serious threat to the environment. This study gathered information and proposes recommendations on the use of digestate in Latvia from nutrient perspective.

Phosphorus (P) is among the most important nutrients required for bacterial growth. It has a great influence on microbial activity even at very small concentrations. Existing chemical methods are not able to determine P at low enough concentrations and to quantify biologically available phosphorus fractions. Therefore, a method of microbially available phosphorus (MAP) determination is used to quantify the amount of P at concentrations below 20 µg/l. Additionally, this method determines the amount of P that can be directly used by microorganisms. Originally it was determined by inoculating sample by Pseudomonas fluorescens (now Ps. brenneri) P17 strain and spread-plated on R2A agar for enumeration. Further, a more rapid method was developed by replacing heterotrophic plate count (HPC) by flow cytometry (FCM). In this paper the use of FCM for MAP determination is validated and compared with HPC method. The results of calibration are presented. The original pure P17 strain was used as inoculum and standards with different PO4-P concentrations were inoculated at 30°C. The gained yield factor by FCM was 1.59x108. FCM results showed strong correlation (R2=0.99) with HPC results, as pure culture was used. Therefore, flow cytometry is a rapid alternative to heterotrophic plate count method for microbially available phosphorus determination.

Importance Quality of life is not a standard primary outcome in ablation trials, even though symptoms drive the indication. Objective To assess quality of life with catheter ablation vs antiarrhythmic medication at 12 months in patients with atrial fibrillation. Design, Setting, and Participants Randomized clinical trial at 4 university hospitals in Sweden and 1 in Finland of 155 patients aged 30-70 years with more than 6 months of atrial fibrillation and treatment failure with 1 antiarrhythmic drug or β-blocker, with 4-year follow-up. Study dates were July 2008–September 2017. Major exclusions were ejection fraction 60 mm, ventricular pacing dependency, and previous ablation. Interventions Pulmonary vein isolation ablation (n = 79) or previously untested antiarrhythmic drugs (n = 76). Main Outcomes and Measures Primary outcome was the General Health subscale score (Medical Outcomes Study 36-Item Short-Form Health Survey) at baseline and 12 months, assessed unblinded (range, 0 [worst] to 100 [best]). There were 26 secondary outcomes, including atrial fibrillation burden (% of time) from baseline to 12 months, measured by implantable cardiac monitors. The first 3 months were excluded from rhythm analysis. Results Among 155 randomized patients (mean age, 56.1 years; 22.6% women), 97% completed the trial. Of 79 patients randomized to receive ablation, 75 underwent ablation, including 2 who crossed over to medication and 14 who underwent repeated ablation procedures. Of 76 patients randomized to receive antiarrhythmic medication, 74 received it, including 8 who crossed over to ablation and 43 for whom the first drug used failed. General Health score increased from 61.8 to 73.9 points in the ablation group vs 62.7 to 65.4 points in the medication group (between-group difference, 8.9 points; 95% CI, 3.1-14.7;P = .003). Of 26 secondary end points, 5 were analyzed; 2 were null and 2 were statistically significant, including decrease in atrial fibrillation burden (from 24.9% to 5.5% in the ablation group vs 23.3% to 11.5% in the medication group; difference –6.8% [95% CI, –12.9% to –0.7%];P = .03). Of the Health Survey subscales, 5 of 7 improved significantly. Most common adverse events were urosepsis (5.1%) in the ablation group and atrial tachycardia (3.9%) in the medication group. Conclusions and Relevance Among patients with symptomatic atrial fibrillation despite use of antiarrhythmic medication, the improvement in quality of life at 12 months was greater for those treated with catheter ablation compared with antiarrhythmic medication. Although the study was limited by absence of blinding, catheter ablation may offer an advantage for quality of life. Trial Registration clinicaltrialsregister.eu Identifier:2008-001384-11

The effect of pipe fittings (mainly T-pieces) on particle accumulation in drinking water distribution networks were shown in this work. The online measurements of flow and turbidity for cast iron, polyethylene and polyvinyl chloride pipe sections were linked with analysis of pipe geometry. Up to 0.29 kg of the total amount mobilized in T-pieces ranging from DN 100/100–DN 250/250. The accumulated amount of particles in fittings was defined as J and introduced into the existing turbidity model PODDS (prediction of discoloration in distribution systems) proposed by Boxall et al. (2001) which describes the erosion of particles leading to discoloration events in drinking water network viz sections of straight pipes. However, this work does not interpret mobilization of particles in pipe fittings which have been considered in this article. T-pieces were the object of this study and depending of the diameter or daily flow velocity, the coefficient J varied from 1.16 to 8.02. The study showed that pipe fittings act as catchment areas for particle accumulation in drinking water networks.

The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and Luria Bertrani (LB) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 26 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration.

Aims Cardiac resynchronization therapy (CRT) may cause changes in ventricular repolarization (VR), particularly in the initial phase of treatment. This study investigated the effect of CRT cessation and re-initiation on parameters of VR duration and heterogeneity at different paced heart rates. Methods Cardiac resynchronization therapy was inactivated for 2 weeks in 16 treatment responders to CRT. QT and JT intervals were measured on the surface electrocardiogram at 60, 70, and 80 bpm (randomized order) and vectorcardiography (VCG) was performed with CRT ‘on’ (day 0), ‘off’ (day 0, 1, 7, and 14) and after CRT re-initiation (day 14, 15, 16, and 21). On day 0 (‘on’) and 14 (‘off’) echocardiography, the 6 min walking distance and brain natriuretic peptide were assessed. Results The QT interval at baseline (CRT ‘on’), measured at 60, 70, and 80 bpm, was 482 ± 31, 468 ± 37, and 457 ± 39 ms, respectively, and decreased by 5, 5, and 6% during the first week following CRT cessation (all P < 0.05). Immediately after re-initiation on day 14, it increased again by 20 ± 18 (4%; P < 0.05), 34 ± 39 (8%; P < 0.01), and 16 ± 38 ms (4%, ns) followed by a gradual decrease towards previous ‘off’ levels. Similar changes were observed for the JT interval. Ventricular repolarization duration was significantly shortened by increasing the paced heart rate from 60 to 70 and 80 bpm. Vectorcardiography parameters reflecting VR gradients (ST-vector magnitude, Tarea, and Tavplan) increased significantly (by 31, 45, and 71%) after CRT cessation. A similar but non-significant pattern was observed after CRT re-initiation. Conclusion The increase in repolarization duration and gradients observed after CRT initiation suggests a transient state of VR instability that can be attenuated by programming of higher paced heart rates during the initial phase of treatment.

The effect of phosphorus addition on survival of Escherichia coli in an experimental drinking water distribution system was investigated. Higher phosphorus concentrations prolonged the survival of culturable E. coli in water and biofilms. Although phosphorus addition did not affect viable but not culturable (VBNC) E. coli in biofilms, these structures could act as a reservoir of VBNC forms of E. coli in drinking water distribution systems.

Effect of microbially available phosphorus (MAP) on biofilm development in drinking water systems was investigated at the pilot-scale experiments over 3 years. Completely mixed biofilm reactors Propella® (water detention time 24 h, flow rate 0.25 m s−1, PVC pipe coupons) were used as water distribution network models. Four experimental runs were carried out with water containing different levels of phosphorus which was limiting nutrient for bacterial growth. Positive correlation between MAP in the inlet water and heterotrophic plate count (correlation coefficient 0.95) in biofilm, as well as for the total bacteria number (correlation coefficient 0.71), was observed. However, our experiments showed that removal of phosphorus down to very low levels (below detection limits of chemical method and MAP

Chemical precipitation in combination with biological treatment is a commonly used method for removal of turbidity and dissolved organic carbon (DOC) from drinking water. DOC is largely removed during biological treatment, which includes ozonation and filtration through a biologically active carbon (BAC) filter. Ozone converts humic substances into a biologically labile form that is mineralised by bacteria living in the following BAC filter. This study shows that this approach is often not efficient for removal of DOC from waters with a high amount of humic substances. During chemical treatment, the microbiologically available phosphorus is very efficiently removed, which results in shortages of phosphorus needed for bacteria to mineralise carbon in BAC filters. To enhance removal of DOC by biological treatment, addition of phosphorus prior to the BAC filters should be considered.

Membranes are widely used for the treatment of various solutions. However, membrane fouling remains the limiting factor for their usage, setting biofouling as the most severe type of it. Therefore, the production of biologically stable water prior to membranes is important. Since lack of phosphorus may hinder the growth of microorganisms, the aim of this research is to evaluate the effect of microbially available phosphorus (MAP) removal via affordable water pre-treatment methods (adsorption, biofiltration, electrocoagulation) on bacterial growth. Four cylindrical reactors were installed at an artificially recharged groundwater station. Further temperature influence and carbon limitation were tested for biofiltration technology. The amount of MAP and total cell count was measured by flow cytometry. The results showed that at lower temperatures electrocoagulation performed the best, resulting in complete MAP removal (detection limit 6.27x10-3μg P l-1). Sorbent demonstrated MAP removal of 70-90%. Biomass did not have any noteworthy results at +8°C, however, at +19°C MAP removal of around 80% was achieved. Main conclusions obtained within this study are: (i) tested technologies effectively eliminate MAP levels; (ii) temperature has a significant effect on MAP removal in a bioreactor, (iii) multi-barrier approach might be necessary for better P limitation that might prolong operating time of a membrane.

The consumption of lactose in acid cheese whey anaerobic fermentation process under fed-batch conditions was studied. During fermentation for 100 hours the biogas production (CO2 and CH4) was analyzed online. Among the standard analyses FT-IR spectroscopy was used to follow the consumption of lactose by bacteria. The absorption bands at 990, 894 and 787 cm-1 in the 2nd derivative spectra were shown to be characteristic for lactose and were used to follow the lactose conversion. It was shown that acid cheese whey lactose was converted by bacteria in first 7 hours. In the spectra of 17, 18 and 95 hour fermentation samples lactose was not identified and these results correlated with the HPLC data.

The addition of labile organic carbon (LOC) to enhance the biodegradation rate of dissolved organic carbon (DOC) in biological columns was studied. Acetate standard solution (NaAc) and LB (Luria Bertrani) medium were used as LOC as biostimulants in glass column system used for measurements of biodegradable dissolved organic carbon (BDOC). The addition of LOC related with the increase of total DOC in sample. The concentration of BDOC increased up to 7 and 5 times and was utilized after 24 min. contact time. The biodegradation rate constant was increased at least 8 times during adaptation-biostimulation period. There was a strong positive correlation between the biodegradation rate constant and the concentration of BDOC. Biostimulation period ranged from 24 to 53 h for NaAc biostimulant and from 20 to 168 h for LB. The study has shown that LOC could be used as stimulator to enhance the biodegradation rate of DOC during biofiltration.

Baktēriju transports un izplatīšanas ūdens padeves sistēmās ir jākontrolē. Simulācijas rīki ir nepieciešami, lai varētu veikt efektīvu baktēriju koncentrācijas monitoringu. Daudzi autori pētīja baktēriju augšanu ūdensvados. Tika mēģināts izstrādāt modeli baktēriju augšanas simulācijai ūdensvados. Tika pievērsta uzmanība arī faktoriem, kas ietekmē baktēriju augšanu. Diemžēl, ir dažādas problēmas, kas apgrūtina modeļa izveidošanu. Piemēram, baktēriju augšanu ietekmē daudzi faktori, tātad jāizvēlas svarīgākie, jo pilnīgi visus faktorus ņemt vērā nav iespējams. Iepriekšējos pētījumos tika izskatīts modelis, ko piedāvāja Zhang et al (2004). Tika paradīts, ka modelis var būt iekļauts Epanet-MSX programmatūra un rezultāti, kas bija iegūti ar EPANET-MSX programmatūras palīdzību bija salīdzināti ar rezultātiem no validētas Fortran programmas. Salīdzinājums paradīja, ka rezultāti ir stipri līdzīgi. Šī pētījuma ietvaros tika pārbaudīta EPANET-MSX modeļa pielietojamība nelielam ūdensvadu tīklam. Rezultāti, kas tika iegūti ar EPANET-MSX programmas palīdzību tika salīdzināti ar rezultātiem, ko ieguva Zhang et al (2004). Tika paradīts, ka rezultāti ir salīdzināmi, tātad var cerēt, ka EPANET-MSX modeli varēs izmantot baktēriju izplatīšanas modelēšanai arī ūdensvadu tīklos.

Bioloģiski degradējamā organiskā oglekļa noteikšana ūdenī: suspendētas un adsorbētas biomasas metožu salīdzināšana. Rakstā salīdzinātas trīs metodes bioloģiski degradējama organiskā oglekļa (BDOC) noteikšanai. Mēs novērtējām metožu atkārtojamību un reproducējamību. Rezultātu salīdzināšanai un datu statistiskai apstrādei, pārbaudīti trīs veidu ūdeņi (dzeramais ūdens, upes ūdens un sintētiskais paraugs) ar trīs dažādām metodēm un divām šo metožu modifikācijām, izmatojot baktēriju suspensiju, fiksēto biomasu pudeļu testā un fiksēto biomasu divu kolonu sistēmā. Pētījuma rezultāti parāda, ka BDOC noteikšanas metožu precizitāte ir līdzīga (4-26%), atšķirībā no tā, ka BDOC variē (no 14% līdz 19% no izšķīduša organiskā oglekļa (DOC) upes ūdenim un no 45% līdz 59% no DOC dzeramajam ūdenim). Turpmākajiem pētījumiem rekomendējam divu kolonu metodi.

Risinājums baktēriju izplatīšanās problēmai ūdensvados tika meklēts vairākos pētījumos. Dažādi autori mēģināja izveidot modeļus, kas dotu iespēju simulēt baktēriju augšanu dzeramā ūdensvada tīklos un noteikt kādi faktori ietekmē baktēriju attīstību. Baktēriju augšanu ietekmē daudzi faktori, kas apgrūtina aprēķinu un ietvert tos visus modelī nav iespējams. Tomēr eksistē modeļi, kas no vienas puses ņem vērā vissvarīgākos faktorus, no kuriem ir atkarīga baktēriju izplatīšanās, un no otrās puses ir pietiekoši kompakti, lai viņus varētu pielietot vidēja līmeņa datoriem, kas ir pieejami laboratorijās. Tomēr jāveic pētījumi ar mērķi salīdzināt dažādus modeļus un pārbaudīt rezultātu atkārtojamību gadījumā, ja rezultāti tiek iegūti ar dažādām modelēšanas programmām. Šajā pētījumā tika salīdzināti rezultāti, kas iegūti ar Fortran IMSL bibliotēku un Epanet-MSX programmas paketi. Zhang et al (2004) piedāvāja matemātisko modeli, kas apraksta baktēriju augšanu ūdensvados. Šajā pētījumā modeļa vienādojumi tika atrisināti taisnas caurules gadījumam, izmantojot Fortran IMSL bibliotēku. Tie paši vienādojumi, izņemot dispersijas locekli tika ievadīti Epanet-MSX vidē. Rezultāti tika salīdzināti savā starpā. Tika atrasts, ka rezultāti, kas bija iegūti ar Fortran IMSL palīdzību, labi sakrīt ar rezultātiem no Epanet-MSX programmas. Var secināt, ka dispersijas loceklis vienādojumos var būt ne īpaši nozīmīgs atsevišķos gadījumos.

Epidemiological studies show that left ventricular hypertrophy (LVH) and hypertension (HT) in coronary artery disease increases the risk for cardiovascular events including sudden cardiac death (SCD). According to experimental studies, myocardial hypertrophy is associated both with altered electrophysiological properties (including prolonged repolarization) and increased vulnerability to ischemia. However, human data to support a repolarization-related mechanism for the increased SCD risk has not been provided. We therefore studied 187 patients undergoing three-dimensional vectorcardiographic monitoring during coronary angioplasty. Eight parameters reflecting different aspects of ventricular repolarization were used: 1) the ST segment (ST-VM and STC-VM), 2) the T vector (QRS-T angle, Televation, and Tazimuth), and 3) the T vector loop (Tavplan, Teigenv, and Tarea). Data collection was performed at rest and at the time of maximum ischemia during coronary occlusion. The patients were divided into three groups: 33 patients with ECG signs of LVH (18 with HT), 54 with HT but without LVH signs, and 100 patients with neither. Coronary artery disease patients with LVH not only had the most abnormal baseline repolarization (as expected) but also a significantly more pronounced repolarization response during coronary occlusion, whereas HT patients had mean parameter values between LVH patients and those without neither HT nor LVH signs. Because there is a relation between increased SCD risk and repolarization disturbances in various clinical settings, the results of the present study are in agreement with animal data and epidemiological observations, although other factors than disturbed repolarization might be of importance.

Pētījums par fosfora ietekmi baktēriju attīstību dzeramā ūdens apgādes sistēmā.

Darbā aprakstīta baktēriju attīstības modelēšana ūdensvada caurulē un Propella® reaktorā. Ņemta vērā temperatūras, barības vielu koncentrācijas un hlora koncentrācijas ietekme. Rezultātu salīdzinājums norādīja, ka matemātiskā modeļa aprakstītās hlora, barības vielu un baktēriju skaita izmaiņas ir līdzīgas gan Propella® reaktorā, gan ūdensvada caurulē.

Pētījums par dzeramā ūdens uzskaites problēmām Rīgā.