Mogućnost proizvodnje električne energije u konvencionalnom sustavu transporta prirodnog plina

The paper presents the possibility of electricity generation at the pressure reduction stations (PRS) in the conventional system of natural gas transmission and distribution. The main deficiency of the conventional system is its thermodynamic irreversibility, i.e. the loss of potential work that could be generated while reducing the gas pressure. Within the first part of work, a thermodynamic model was created to analyze changes in energy and exergy within the gas transport system. The second part of work deals with the application of turboexpanders (expansion turbines) which may be used to generate electricity while reducing the gas pressure. A thermodynamic model of the turboexpander system was created and the relevant thermodynamic indicators were defined. Case studies for two different PRS were performed to analyze the thermodynamic quality and the economic feasibility of turboexpander application for varying design parameters, i.e. the gas preheating rate and the expander isentropic efficiency.Ovaj članak opisuje mogućnost proizvodnje električne energije u mjerno- redukcijskim stanicama (MRS), koje čine dio prijenosnog i distribucijskog plinskog sustava. Glavni nedostatak konvencionalnog sustava je njegova termodinamička nepovrativost, to jest gubitak rada koji bi mogao biti generiran pri redukciji tlaka plina. U prvom je dijelu ovog rada bio izrađen model za analizu promjena energije i eksergije u sustavu transporta plina. U drugom se dijelu rada razmatra upotreba turboekspandera (turbina) za proizvodnju električne energije pri redukciji tlaka plina. Izrađen je termodinamički model sustava s turboekspanderom i definirani su odgovarajući termodinamički pokazatelji.Razrađeni su primjeri za dvije različite MRS, u kojima je analizirana termodinamička kvaliteta i ekonomska opravdanost projekata turbine pri različitim projektnim parametrima, to jest stupanj predgrijavanja plina i iskoristivost turbine

Drug addiction: theories and hypotheses

Uzależnienie jest złożonym zaburzeniem funkcjonowania centralnego układu nerwowego, charakteryzującym się utratą kontroli nad poszukiwaniem i przyjmowaniem narkotyku oraz ryzykiem nawrotu, nawet po długim okresie abstynencji. Choroba ta może mieć swoje źródło w zaburzeniach działania układu nagrody w mózgu, zaburzonym uczeniu asocjacyjnym i zaburzonej równowadze zachowań popędowych, które kontrolują reakcje apetytywne ukierunkowane na szukanie kontaktu z substancją uzależniającą. W niniejszej pracy omawia się pojęcia i teorie uzależnienia i postuluje się, że upośledzenie zaspokajania popędu prowadzi do trwałej aktywacji związanej z aktualnym popędem związanym z narkotykiem, co prowadzi do głodu narkotykowego i nawrotów zachowań nałogowych.Drug addiction is a complex disorder of the central nervous system, characterized by the loss of control over drug seeking and drug taking, and by the risk of relapse, even after a long period of abstinence. This disease may have its source in a disturbed function of brain reward system, disturbed associative learning and a disturbed balance of drive-related behaviors, which control appetitive reactions aimed at seeking contact with an addictive substance. Here we review concepts and theories of drug addiction and postulate that dysfunction of drive satisfaction leads to the sustained activation related to the current drug-related drive thus leading to the drug craving and relapses of addictive behavior

Współczesne kierunki badań nad patomechanizmem stresu i depresji i ich znaczenie w kształtowaniu poglądów na działanie leków przeciwdepresyjnych

Recent laboratory and clinical studies are producing real improvements in our understanding the stress, depression as well as mechanism of action of antidepressant drugs. In particular, the broadening of our understanding of the role of HPA axis in depression is opening new strategies for pharmacotherapy of depression. It has been reported that acute depression is characterized by hypersecretion of CRH, ACTH and cortisol. On the other hand, in chronic depression cortisol remained elevated while ACTH levels are reduced. Antagonists of CRH and cortisol could therefore, represent a new gneration of antidepressants. Further, recent clinical studies have shown antidepressant efficacy of melatonin agonists, in particular agonists of MT-1 receptors, thus suggesting that these compounds hold promise for use as novel antidepressants. Finally, laboratory studies have been found that the molecular basis of antidepressant action involves postreceptor components such as second messenger systems, protein kinases and transcription factors. Antidepressant drugs have also been reported to stimulate the production of neurotropic factors and neurotrophins thus counteracting the neurodegenerative processes associated with stress and depression. Therefore, it has become apparent that antidepressants share mechanisms beyond the monoamine synapse. These mechanisms seem to be at least as important as the monoaminergic ones.Nowsze badania laboratoryjne i kliniczne prowadzone w ciągu ostatnich kilkunastu lat poszerzyły znacznie wiedzę na temat patomechanizmu stresu i depresji, zwłaszcza w zakresie roli osi podwzgórze-przysadka-nadnercza (HPA). Wykazano na przykład, że o ile w ostrej fazie depresji występuje nadmierne wydzielanie CRH, ACTH i kortyzolu, to w depresji chronicznej wydzielanie ACTH się zmniejsza. Wynika to prawdopodobnie z silnego zwrotnego hamującego wpływu kortyzolu. Nowe strategie terapeutyczne mogą się zatem wiązać z wprowadzeniem antagonistów CRH i kortyzolu. Pewne nadzieje budzą też agoniści melatoniny, w szczególności agoniści receptorów MT-1. Rozszerzyła się też znacznie wiedza o mechanizmach molekularnych związanych z działaniem leków przeciwdepresyjnych, szczególnie w zakresie wtórnych przekaźników komórkowych, kinaz białkowych i czynników transkrypcyjnych. Istotne znaczenie ma też nasilanie przez leki przeciwdepresyjne wydzielania czynników wzrostu neuronów (neurotropowych). Mechanizmy hormonalne i zmiany na poziomie molekularnym mogą stanowić ważny mechanizm działania leków przeciwdepresyjnych, wykraczający poza synapsy monoaminergiczne

Thermoecological cost of electricity, heat and cold generated in a trigeneration module fuelled with selected fossil and renewable fuels

The paper presents a thermoecological evaluation of a trigeneration module based on an Internal Combustion Engine fuelled with selected fuels of various origin: domestic/mixed-origin natural gas, CMM (coal mine methane) and biogas. The generated products comprise: electric energy, heat available in hot water and cold generated in an absorption chiller. Transformations of energy and exergy in the trigeneration module have been analysed, and the TEC (thermoecological cost) of the products has been determined. The decomposition of TEC into the cost of resources, the contribution of process irreversibility and the equivalent cost of noxious substances has been shown. The chosen gaseous fuels reflect four different cases: a fossil, non-renewable resource (1 – domestic, 2 – mixed origin) 3 – a by-product from the extraction of a fossil resource and 4 – a renewable resource. It has been demonstrated how the TEC of final products depends on the chosen resource, on the process irreversibility, and on the waste contribution. TEC of electricity produced in the trigeneration module varies from 0.30 (biomass syngas) to 3.11 (mixed origin natural gas), and the TEC of the generated heat and cold varies from 0.61 to 6.46 (heat) and 3.37 and 35.5 (cold) accordingly

Tryptophan Oxidative Metabolism Catalyzed by Geobacillus Stearothermophilus: A Thermophile Isolated from Kuwait Soil Contaminated with Petroleum Hydrocarbons

Tryptophan metabolism has been extensively studied in humans as well as in soil. Its metabolism takes place mainly through kynurenine pathway yielding hydroxylated, deaminated and many other products of physiological significance. However, tryptophan metabolism has not been studied in an isolated thermophilic bacterium. Geobacillus stearothermophilus is a local thermophile isolated from Kuwait desert soil contaminated with petroleum hydrocarbons. The bacterium grows well at 65 °C in 0.05 M phosphate buffer (pH 7), when supplied with organic compounds as a carbon source and has a good potential for transformation of steroids and related molecules. In the present study, we used tryptophan ethyl ester as a carbon source for the bacterium to study the catabolism of the amino acid at pH 5 and pH 7. In this endeavor, we have resolved twenty one transformation products of tryptophan by GC/LC and have identified them through their mass spectral fragmentation

1973: Abilene Christian College Bible Lectures - Full Text

JESUS Being the Abilene Christian College Annual Bible Lectures 1973 Published by ABILENE CHRISTIAN COLLEGE BOOK STORE ACC Station Abilene, Texas 7960

Phenotypic plasticity of nest-mate recognition cues in formica exsecta ants

It is well established that many ant species have evolved qualitatively distinct species-specific chemical profile that are stable overlarge geographical distances. Within these species profiles quantitative variations in the chemical profile allows distinct colony-specific odours to arise (chemotypes) that are shared by all colony members. This help maintains social cohesion, includingdefence of their colonies against all intruders, including con-specifics. How these colony -level chemotypes are maintainedamong nest-mates has long been debated. The two main theories are; each ant is able to biochemically adjust its chemical profileto‘match’that of its nest-mates and or the queen, or all nest-mates share their individually generated chemical profile viatrophollaxis resulting in an average nest-mate profile. This‘mixing’idea is better known as theGestaltmodel. Unfortunately,it has been very difficult to experimentally test these two ideas in a single experimental design. However, it is now possible usingthe antFormica exsectabecause the compounds used in nest-mate recognition compounds are known. We demonstrate thatworkers adjust their profile to‘match’the dominant chemical profile within that colony, hence maintaining the colony-specificchemotype and indicates that a‘gestalt’mechanism, i.e. profile mixing, plays no or only a minor role

Compressible Fanno Flow in Micro-Channels: an enhanced quasi-2D numerical model for laminar flows

© 2019 The Authors. Micro-scale fluid systems are becoming common in many applications ranging from electronic cooling to refrigeration systems and more. One-dimensional numerical models represent a simple and fast tool for the design of such devices, yet they struggle to accurately predict the flow characteristics in compressible micro-flows. Under the adiabatic assumption, the elegant theory developed by Fanno allows models for the viscous compressible flow in constant cross-section channels to be easily built. Although reasonably accurate, these models suffer from drawbacks inherent to their being one-dimensional, as such they cannot take into account the local profiles of quantities like the velocity and the temperature. In cascade, this results into incorrect evaluations of other dependent quantities, such as the dynamic pressure and the fluid thermophysical properties. The mismatch turns large when the fluid compressibility becomes important. As the Mach number grows, the velocity profile changes, and so the friction factor, even though a reliable model for predicting this change is still missing. In fact, a constant friction factor throughout the channel is generally assumed, following the incompressible flow theory. Here, a set of correlations is proposed improving the 1D theory accuracy by taking into account the effects of the non-uniform velocity and temperature profiles in a quasi-2D fashion. A detailed analysis of the velocity profiles at different Mach numbers coming from a large set of CFD simulations results in a model for assessing the impact of compressibility on friction and other quantities. The numerical model proposed, being able to properly account for the compressibility effects, offers an improved tool for the design of micro-scale fluid systems. Extending the analysis to include heat transfer is not difficult as the effect of heat flux will be analogous to the effect of pressure drop due to friction