bluuebunny/crossref_metadata_2025 huggingface dataset:
Inference of Chemical Reaction Networks Using Hybrid S-system Models
Authors: Searson Dominic P , Willis Mark J , Horne Simon J , Wright Allen R
Published: March 2007

This article demonstrates, using simulations, the potential of the S-system formalism for the inference of unknown chemical reaction networks from simple experimental data, such as that typically obtained from laboratory scale reaction vessels. Virtually no prior knowledge of the products and reactants is assumed. S-systems are a power law formalism for the canonical approximate representation of dynamic non-linear systems. This formalism has the useful property that the structure of a network is dictated only by the values of the power law parameters. This means that network inference problems (e.g. inference of the topology of a chemical reaction network) can be recast as parameter estimation problems. The use of S-systems for network inference from data has been reported in a number of biological fields, including metabolic pathway analysis and the inference of gene regulatory networks. Here, the methodology is adapted for use as a hybrid modelling tool to facilitate the reverse engineering of chemical reaction networks using time series concentration data from fed-batch reactor experiments. The principle of the approach is demonstrated with noisy simulated data from fed-batch reactor experiments using a hypothetical reaction network comprising 5 chemical species involved in 4 parallel reactions. A co-evolutionary algorithm is employed to evolve the structure and the parameter values of the S-system equations concurrently. The S-system equations are then interpreted in order to construct a network diagram that accurately reflects the underlying chemical reaction network.
Enhanced Explicit Scheme to Solve Transient Heat Conduction Problem
Authors: Hegde Ganesh , Gattumane Madhu
Published: March 2007

Improvement in accuracy without sacrificing stability and convergence of the solution to unsteady diffusion heat transfer problems by computational method of enhanced explicit scheme (EES), has been achieved and demonstrated, through transient one dimensional and two dimensional heat conduction. The truncation error induced in the explicit scheme using finite difference technique is eliminated by optimization of partial derivatives in the Taylor series expansion, by application of interface theory developed by the authors. This theory, in its simple terms gives the optimum values to the decision vectors in a redundant linear equation. The time derivatives and the spatial partial derivatives in the transient heat conduction, take the values depending on the time step chosen and grid size assumed. The time correction factor and the space correction factor defined by step sizes govern the accuracy, stability and convergence of EES. The comparison of the results of EES with analytical results, show decreased error as compared to the result of explicit scheme. The paper has an objective of reducing error in the explicit scheme by elimination of truncation error introduced by neglecting the higher order terms in the expansion of the governing function. As the pilot examples of the exercise, the implementation is aimed at solving one-dimensional and two-dimensional problems of transient heat conduction and compared with the results cited in the referred literature.
Advanced Modeling of Reactive Separation Units with Structured Packings
Authors: Kenig E. Y
Published: March 2007

Reactive separations combining mass transfer with simultaneous chemical reactions within a single column unit provide an important synergistic effect and bring about several advantages. The influence of column internals in reactive separations increases significantly, because these internals have to enhance both separation and reaction and maintain a sound balance between them. To solve this problem, a novel generation of column internals with enhanced mass transfer performance and low pressure drop has been created. Among them, corrugated packings of the regular type or structured packings have gained a wide acceptance.This paper gives a state-of-the-art review of the structured packings modeling methods, focusing on two innovative and particularly promising approaches. The first of them is based on the application of CFD, whereas the second one employs the idea of hydrodynamic analogy between complex and simple flow patterns. Both approaches are illustrated with several case studies.
The Pro-collusive Effect of Increasing the Repose Period for Price Fixing Agreements
Authors: Hinloopen Jeroen
Published: March 2007

Intuitively, extending the period of repose for price fixing agreements enhances the effectiveness of competition policy enforcement. This paper proves this intuition wrong. As extending the repose period reduces cartel members' defection payoff while it leaves unaltered expected compliance profits, it induces cartels to be more stable internally.
The Transactions Demand for Credit Cards
Authors: Johnson Kathleen W.
Published: March 2007

I argue that the measure of credit card debt used by researchers has grown rapidly in part because it captures debt arising from transactions in which a credit card is used because of its advantages over other payment instruments. Increases in debt stemming from such use may not signal greater household financial vulnerability if households are willing and able to repay this short-term debt. However, it may suggest that the cost of using credit cards to pay for purchases has declined relative to other payment instruments. I conclude that had transactions demand remained at its real 1992 levels, rather than growing almost 15 percent per year, measured credit card debt would have grown a bit less than 1 percentage point slower per year between 1992 and 2001. Moreover, I show that removing transactions demand from aggregate consumer credit can alter conclusions about the relationship between credit and consumption.
Market Power Effects on Market Equilibrium in Ambient Permit Markets
Authors: Schwartz Sonia
Published: March 2007

This paper discusses market power effects in ambient permit markets. We consider a dominant firm in a position to exert market power in several markets. A first conclusion is that the distortion observed on manipulated markets spreads to other markets. We find that the manipulated prices could be lower than their competitive level if the dominant firm acts as a monopolist, and higher if it acts as a monopsonist. We show that the efficient outcome is not reached, except if the number of firms is the same as the number of markets whatever the initial endowment of permits. If not, the efficient outcome can be reached by means of initial endowments.
The Marginal Propensity to Spend on Adult Children
Authors: Altonji Joseph G , Villanueva Ernesto
Published: March 2007

We use mortality rates and age specific estimates of the response of transfers and wealth to lifetime resources to estimate how much of an extra dollar of parental lifetime resources will ultimately be passed on to adult children in the form of inter vivos transfers and bequests. We find that parents pass on between 2 and 3 cents of an extra dollar of expected lifetime resources in bequests and about 3 cents in transfers, which together amount to about one fifth of our rough estimate of the marginal propensity to spend on children under 18 and on college. The value of .4 relating earnings of the child to earnings of the parent rises to about .46 when the effect of parental earnings on bequests and transfers is added on, although the estimate is lower for nonwhites and varies with assumptions about the intergenerational earnings correlation and the number of children.
State Graduation Requirements, High School Course Taking, and Choosing a Technical College Major
Authors: Federman Maya
Published: March 2007

I examine the changing patterns of enrollment of females and males in mathematics and science courses in high school between roughly the classes of 1982 and 1992. Course taking has increased in both subjects and, notably, the gender gap has closed. I also examine the impact of state graduation requirements on course taking patterns for males and females. Higher graduation requirements in mathematics and science are associated with increased course taking and the magnitude is similar for both females and males. Finally, I investigate the relationship between high school math and science course taking and college major choice for the latter cohort. Ability and taste are likely to affect both high school course selection and college major and students planning on choosing a technical major are more likely to choose to take additional math and science courses in high school. To address this issue of selection bias, I first include direct measures of ability and taste and then use variation in state graduation requirements to instrument for increased course taking. I find that the number of high school mathematics courses taken has a positive effect on the probability that a student chooses a technical major in college and that this result appears robust to correction for selection bias.
A Model of Dysfunctional Urges and Addiction with an Application to Cigarette Smoking
Authors: Glazer Jacob , Weiss Andrew M
Published: March 2007

We model economic decisions as stemming from urges. The magnitude of the urge is a function of previous consumption. Welfare gains from satisfying an urge vary with the nature of the urge. An urge is "dysfuntional" if people are willing to incur costs to stop themselves from gratifying that urge. The simple framework we develop captures the essential features of other, more complex models of addiction and problems of self control. We apply the model to analyze cigarette smoking. Our main results are that, under not implausible conditions, making cigarettes more addictive can reduce smoking and making cigarettes more harmful can improve the average health of the population.
Gasoline Price Differences: Taxes, Pollution Regulations, Mergers, Market Power, and Market Conditions
Authors: Chouinard Hayley H , Perloff Jeffrey M
Published: March 2007

Retail and wholesale gasoline prices vary over time and across geographic locations due to differences in government policies and other factors that affect demand, costs, and market power. We use a two-equation, reduced-form model to determine the relative importance of these various factors using panel data for 48 states over nine years. We find that the variation in the price of crude oil has been virtually the only major factor contributing to gasoline price variations during the 1990s. Tax variations and mergers contribute substantially more to geographic price differentials than do price discrimination, cost factors, or pollution controls.
Disability Testing and Retirement
Authors: Cremer Helmuth , Lozachmeur Jean-Marie , Pestieau Pierre
Published: March 2007

We study the design of retirement and disability policies and illustrate the often observed exit from the labor force of healthy workers through disability insurance schemes. In our model, two types of individuals, disabled and leisure-prone ones, have the same disutility for labor and cannot be distinguished. However, they are not counted in the same way in social welfare. We determine first- and second-best optimal benefit levels and retirement ages. Then we introduce the possibility of testing that can sort out disabled workers from healthy but retirement-prone workers. We show that such testing can increase both social welfare and the rate of participation of elderly workers; in addition disabled workers are better taken care of. It is not optimal to test all applicants. Surprisingly, the (second-best) solution may imply later retirement for the disabled than for the leisure-prone. In that case, the disabled are compensated by higher benefits.
The Short and Long Run Effects of Daylight Saving Time on Fatal Automobile Crashes
Authors: Sood Neeraj , Ghosh Arkadipta
Published: March 2007

Prior literature suggests that Daylight Saving Time (DST) can both increase the risk of automobile crashes in the short run and decrease the risk of automobile crashes in the long run. We use 28 years (1976-2003) of automobile crash data from the United States, and exploit a natural experiment arising from a 1986 federal law that changed the time when states switched to DST to identify the short run and long run effects of DST on automobile crashes. Our findings suggest that (1) DST has no significant detrimental effect on automobile crashes in the short run; (2) DST significantly reduces automobile crashes in the long run with a 8-11% fall in crashes involving pedestrians, and a 6-10% fall in crashes for vehicular occupants in the weeks after the spring shift to DST.
Academic Journal Prices in a Digital Age: A Two-Sided Market Model
Authors: McCabe Mark J , Snyder Christopher M.
Published: March 2007

Digital-age technologies promise to revolutionize the market for academic journals as they have other media. We model journals as intermediaries linking authors with readers in a two-sided market. We use the model to study the division of fees between authors and readers under various market structures, ranging from monopoly to free entry. The results help explain why print journals traditionally obtained most of their revenue from subscription fees. The results raise the possibility that digitization may lead to a proliferation of online journals targeting various author types. The paper contributes to the literature on two-sided markets in its analysis of free-entry equilibrium and modeling of product-quality certification.
The Effect of Smoking Bans on Bars and Restaurants: An Analysis of Changes in Employment
Authors: Adams Scott , Cotti Chad D.
Published: March 2007

Many communities and several states prohibit smoking in bars or restaurants. Using county-level data on employment from across the US, we find that communities where smoking is banned experience reductions in bar employment compared with counties that allow smoking. Smoking bans have a larger detrimental impact on bars in geographic areas with a high prevalence of smokers. The relative effect on restaurant employment is neutral or mildly positive. The positive effects are concentrated in areas with fewer smokers. We also find that bans have a positive effect on restaurant employment in warmer regions of the country, especially during the cooler winter months, and in the summer in colder regions. This suggests the prevalence of outdoor seating might influence the policy's effect.
Information Goods Upgrades: Theory and Evidence
Authors: Viard V. Brian
Published: March 2007

A substantial portion of information goods is sold through upgrades. I model a monopolist offering successive generations of an information good in a dynamic model. In each period, the monopolist offers up to two prices for each generation: a full price to those who have never purchased and a version upgrade price to consumers who own a previous generation. I employ an overlapping generations model with infinite-lived firms and consumers that reflects the effect of future profits on current decisions better than previous two-period models. The model's predictions accord well with data from the PC software industry. The model explains why: 1) firms issued version upgrades with every new generation, 2) firms provided a discount to those upgrading relative to first-time buyers and 3) late adopters commonly purchased the latest version at full price even though some earlier adopters with higher valuations did not upgrade to the latest version.
Staged Financing with a Variable Return
Authors: Smirnov Vladimir , Wait Andrew
Published: March 2007

This paper explores the hold-up problem between two parties (an entrepreneur and an investor) when one of the parties (the entrepreneur) is unable to commit not to repudiate the initial contract. To mitigate hold-up we allow the parties to stage investments over time and derive the optimal investment path in a model that places no restrictions on the growth of collateral. Our model predicts that neither positive wealth of the entrepreneur nor the lack of discounting ensures that all profitable projects proceed. We also derive necessary and sufficient conditions for the project to be financeable when there are no costs of delay.
A Note on Generating Globally Regular Indirect Utility Functions
Authors: Conniffe Denis
Published: March 2007

Despite their scarcity in the literature, an abundance of globally regular indirect utility functions, involving as many parameters as desired, exist and are easily constructed as a function of simple homothetic component utilities.
Firm Size, Productivity, and Manager Wages: A Job Assignment Approach
Authors: Grossmann Volker
Published: March 2007

Ability of managers and other nonproduction professionals is key for the productivity of firms. Hence, the assignment of heterogeneous nonproduction workers across firms determines the distribution of productivity. In turn, the transmission of productivity differences into profit differences -- resulting from product market competition -- determines firms' willingness to pay for higher managerial skills. This paper explores the equilibrium assignment of nonproduction workers across ex ante identical firms which results from this interaction between product market and the market for nonproduction skills. The analysis suggests that, typically, large and productive firms coexist with small, low-productivity firms. Consistent with empirical evidence, a skewed distribution of firm size tends to arise. Moreover, the model predicts a positive relationship of firm size to productivity, manager quality, and manager remuneration. Finally, according to comparative-static analysis, higher intensity of product market competition can account for increases in the compensation at the top of the wage distribution.
Equilibria in Multi-Unit Discriminatory Auctions
Authors: Anwar Ahmed W
Published: March 2007

We extend Milgrom and Weber's affiliated valuations model to the multi-unit case. We show that the discriminatory auction has a unique equilibrium, that corresponds to Milgrom and Weber's first-price equilibrium in the 2-bidder, constant marginal valuations case. This unique equilibrium therefore leads to lower expected prices than the equilibrium of the English auction where the units are bundled together. Hence we show that in an auction of a single object where the object can be divided into k parts and a bidder's valuation for each part is the same, it is not possible to increase revenue by using a multi-unit discriminatory auction. With more than two bidders and constant marginal valuations we show that the first-price equilibrium is an equilibrium of the multi-unit discriminatory auction. Back and Zender show this in the common values case which is a special case of affiliated valuations. We also show that the first-price equilibrium does not hold with decreasing marginal valuations.
Value Maximization as an Ex-Post Consistent Firm Objective When Markets are Incomplete
Authors: Sabarwal Tarun
Published: March 2007

In competitive economies with private firm ownership, incomplete markets, and firm shareholders changing over time, several firm objectives have been proposed. Some are useful to understand efficiency of equilibria, and others are explicitly consistent with majority shareholder control or collective choice rules, but it is not always clear if versions of each type are consistent with versions of the other type. This paper shows that ex-post, value maximizing rules, (including those proposed by Dreze, and Grossman and Hart,) are consistent with shareholder preferences in such economies; that is, along the equilibrium path, in every period and state of the world, every coalition of a firm's shareholders in that period and state approves a value maximizing production plan. This result applies to cases when shareholders within a firm and across firms can form coalitions, and when stock trading can be ex-dividend or cum-dividend, and with a combination of both. This result does not resolve the problem of inefficiency of stock market equilibria, or that of ex ante disagreement among shareholders. It can help understand when firm objectives with some desirable properties are consistent with a particular version of shareholder control, and it provides a stability criterion (in terms of robustness to shareholder coalitions) for organizing productive resources in such economies.
Application of mri for improved local control in complex radiotherapy of cervical cancer
Authors: Hadjiev Janaki , Cselik Zsolt , Bogner Péter , Kovács Árpád , Lakosi Ferenc , Kotek Gyula , Repa Imre
Published: March 2007

Background: The aim of this study was to analyze the use of magnetic resonance imaging (MRI) as a modern medical imaging technique in radiotherapy with special emphasis on the integration of MRI and a novel technique in brachytherapy to optimize treatment outcome in cervical cancer. Methods: In addition to the CT based shrinking volume conformal teletherapy in 31 patients with locally advanced cervical cancer, MRI examination with a special adjustable applicator at the treatment site was performed for the brachytherapy planning. To avoid excessive doses to the healthy structures during complex cervical radiotherapy isodose curves were calculated upon the information of the MR image and dose distribution was evaluated. Results: The consecutive application of CT and MRI limited the possibility for overdosage of the critical organs and undertreatment of the advanced tumor spread in all cases. The overall response rate for the complex treatment was 74.2% with complete regression in 25.8% of the cases. Based on the exact information of the three dimensional digital data radiation doses could be optimized without increasing the possibility of acute complications rate. Conclusion: The introduction of 3D treatment planning for teletherapy pelvic and boost irradiation of cervical carcinoma as well as for the brachytherapy part of the complex treatment is to be recommended. .
The role of estrogen receptors isoforms in breast cancer
Authors: Mandusic Vesna , Nikolic-Vukosavljevic Dragica , Neskovic-Konstantinovic Zora , Tanic Nikola , Celeketic Dusica , Dimitrijevic Bogomir
Published: March 2007

Background: Estrogen and progesterone receptor (ER/PR) status is an accepted predictive marker in breast cancer. It is well known that breast tumors, which are ER(+) are more likely to respond to endocrine therapy. However, certain percentage of ER(+)/PR(+) tumors do not respond to endocrine therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ER?), as well as the existence of numerous isoforms/splice variants of both ER? and ER?, suggests that complex regulation of estrogen action exists. In this study, we analyze does the expression of two ER? isoforms correlates with ER?/PR status. Methods: Sixty samples of primary operable breast carcinomas were analyzed for ER? and PR protein levels and for mRNA expression of two ER? isoforms (ER?1 and ER??5). ER? and PR proteins were measured by classical biochemical techniques, and ER? mRNAs were measured by real-time RT-PCR. Results: Tumors are divided in three groups according to relative level of mRNA for ER?1 and ER??5. We found that there is no correlation of ER?1 mRNA expression with ER? and PR protein levels. We confirmed the existence of inverse correlation of ER??5 with PR and of ER??5 with ER? in the group of postmenopausal patients. In the subsets of tumors defined by ER?/PR status, we found that percentage of tumors, which concomitantly expressed high levels of both transcripts, are parallel with those that do not response to tamoxifen treatment. Conclusion: Inverse correlation of ER? with ER??5 and PR with ER??5isoform suggests that ER??5 may have inhibitory effect on ER? activity in postmenopausal patients. In addition, we point out that determination of expression profiles of ER? and ER? isoforms in the defined groups of patient are necessary for elucidating its involvement in endocrine resistance. .
Diet as a risk factor of cancer among the population of Nis
Authors: Nikolic Maja , Mitrovic Vladimir , Lukic Natasa , Lazarevic Konstansa
Published: March 2007

Background: Objective of the study was to determine the differences in distribution of the most important nutritional risk factors for cancer among healthy population of Nis, men and women, in order to carry out adequate measures of prevention. Methods: 388 people were involved in the study, randomly selected and they completed the authorized questionnaire concerning their eating habits, marital status and smoking habits. Body mass index was determinated also. Participants? nutritive profile concerning risk factors was determined by giving points to each factor such as number of daily portions of fruits, vegetables, and cereal, daily intakes of red meat, table salt, and alcohol and obesity. ?2-test was applied to determine if there is statistically significant difference among risk factors concerning sex and marital status. Student t-test was applied to determine if there is statistically significant difference among medium values of points of risk concerning sex and marital status. Results: According to the results, the population of Nis is at medium risk for cancer. The number of points between 18 and 27 was considered medium risk. Women are at lower risk to develop cancer than men (t=6.66, p>0.01), regarding nutritional risk factors, the some for singles (t=2.38, p>0.01). Vegetables (?2=3.29, p<0.01) and salt (?2=2.15, p<0.01) intake was not statistically different among men and women, while cereal (?2=10.96, p<0.01), alcohol (?2=13.48, p<0.01), and table salt (?2=29.01, p<0.01), intake was higher among singles. Singles were of heavier weight than married ones (?2 = 19.66, p<0.01). Conclusion: Prevention of cancer should be based on higher intake of fruit and lower intake of red meat, as well as, giving up smoking and alcohol and regulating weight. .
Identifying and testing for hereditary susceptibility to breast/ovarian cancer in Serbia: Where are we now?
Authors: Brankovic-Magic Mirjana , Dobricic Jelena , Jankovic Radmila , Konstantopoulou Irene , Yannoukakos Drakoulis , Radulovic Sinisa
Published: March 2007

About 90% of all breast cancers can be considered as sporadic, without inherited gene alteration. The rest of breast cancers (about 5 to 10%) are considered hereditary, most commonly caused by alterations of BRCA1/2 tumor suppressor genes. Lifetime risks for breast and ovarian cancers are increased among BRCA1/2 mutation carriers - 4 to 8 and 10 to 20 fold higher respectively. Due to the small proportion of hereditary form of disease, as well as to the high cost, BRCA testing is not screening test for general population. It is addressed to selected part of population that fit to recommended criteria. Full coding region sequencing of both genes is "gold standard" for detection of BRCA mutation. Concerning BRCA testing in Serbia, complete or partial sequencing of BRCA1/2 coding region was performed in 60 samples. The presence of 4 BRCA1 known mutations, previously detected elsewhere, has been shown: 185delAG, C61G, 3447del4 and 5382insC (detected twice). In BRCA1 gene, exon 16, an unclassified variant M1652I was found. Polymorphic variants in BRCA1 (8 polymorphisms) and BRCA2 (5 polymorphisms) genes were also detected. The majority of found BRCA1 and BRCA2 polymorphic variants are the missense ones and their influence on breast/ovarian cancer risk in our population has to be proved. Identification of BRCA mutations carriers and establishment of spectra and frequency of BRCA mutations should enable introduction of BRCA1/2 testing into the clinical practice of Serbia. .
Matrix metalloproteinases in the process of invasion and metastasis of breast cancer
Authors: Konjevic Gordana , Stankovic Sandra
Published: March 2007

Metastatic cascade in malignant tumors, including breast cancer, starts with localized invasion of the host tissue. This process, requiring that tumor cells separate from each other, includes loss of homotypic and heterotypic cell adhesion and cell-cell contact inhibition, acquisition of motility, exacerbated by "epithelial-to-mesenchymal transition", and production of proteolytic enzymes which degrade basal membrane and extracellular matrix. In this sense, aside from urokinase type plasminogen activator, increased expression and activity of matrix metalloproteinases (MMPs) is one of the earliest and most sustained events in tumor progression, playing a role in angiogenesis, invasion and metastasis. MMPs are a family of 23 zinc metalloproteinases, secreted as latent pro-enzymes, activated by proteolytic cleavage, and inhibited by the tissue inhibitors of metalloproteinases. The most commonly connected MMPs with the processes of metastasis are MMP-2 (gelatinase A) and MMP-9 (gelatinase B), due to their ability to degrade collagen type IV, major component of vascular basement membrane. MMP-2 and MMP-9 are also required for the switch to the "angiogenic phenotype" during tumor progression and activation of dormant tumor cells. The association of the increase in serum MMP-2 and MMP-9 activity and clinical stage suggests the usefulness of these parameters as markers in the follow-up and prognosis of breast cancer patients. The concept of "stromal-directed therapy" of cancer, with MMP-inhibitors directed against MMPs as targets, is based on the observed MMP up-regulation in tumors.
Cross-talk between ER and HER2 in breast carcinoma
Authors: Todorovic-Rakovic Natasa , Neskovic-Konstantinovic Zora , Nikolic-Vukosavljevic Dragica
Published: March 2007

In tumors in which estrogen receptor (ER) and growth factor signaling pathways are simultaneously active, there is a bidirectional cross-talk that results in a positive feedback cycle of cell survival and proliferation stimuli. Beside the postulated inverse correlation between ER and HER2 (human epidermal growth factor receptor 2) as a consequence of repressive feedback signaling loop, there are also other mechanisms regarding ER-HER2 interactions. It seems that MAPK (mitogen-activated protein kinase) pathway has a central role in synergistic action between ER and HER2 in normal mammary gland development, as well in the breast cancer. MAPK pathway is hyperstimulated in cells that overexpress HER2 as a consequence of HER2 gene amplification. In ER+ tumors, MAPK phosphorylates and activates either ER itself or ER coregulators, enhancing the transcriptional activation potential of ER. ER and HER2 signaling could interact on multiple levels (genomic or non-genomic) and therefore might induce reduced ER expression or might increase ER function. Based on our own research, dominant effect of postulated cross-talk was not related to HER2-induced reduced expression of ER (no difference in quantitative levels of ER in ER+ tumors regarding their HER2 status and no difference in progression-free time between ER+HER2- and ER+HER2+ patients) as presented. The importance of understanding ER-HER2 cross-talk is not only because of its significance in breast cancer progression, but because it seems to be fundamental factor in endocrine resistance that can improve treatment strategies, especially targeting MAPK pathway. .
First total synthesis and biological evaluation of halolitoralin A
Authors: Dahiya Rajiv , Pathak Devender
Published: March 2007

Anew potent bioactive alanine-rich cyclic hexapeptide halolitoralin A(8), which was previously isolated from the marine sediment-derived bacterial strain Halobacillus litoralis YS3016, has been synthesized by the solution phase technique. All the coupling reactions were performed at room temperature utilizing dicyclohexylcarbodiimide (DCC) as the coupling reagent and N-methylmorpholine (NMM) as the base. The structure of the peptide was characterized by IR, 1H-NMR, 13C-NMR, FAB MS spectral data, as well as elemental analysis and DSC. The synthesized cyclopeptide was also screened for its antimicrobial and anthelmintic activities and found to exhibit potent antifungal activity against the pathogenic fungi Candida albicans and Trichophyton mentagrophytes along with potent antibacterial activity against the gram negative bacteria Pseudomonas aeruginosa and Escherichia coli. Gram negative bacteria were found to be more sensitive than gram positive bacteria towards the newly synthesized peptide. In addition, the peptide was also found to exhibit moderate anthelmintic activity against the earthworms Megascoplex konkanensis and Eudrilus sp. .
Synthesis and application of new mordent and disperse azo dyes based on 2,4-dihydroxybenzophenone
Authors: Dixit Bharat , Patel Hitendram , Desai Dhirubhai
Published: March 2007

Novel mordent and disperse azo dyes were prepared by the coupling of various diazo solutions of aromatic amines with 2,4-dihydroxybenzophenone. The resultant dyes were characterized by elemental analyses as well as IR and NMR spectral studies. The UV-visible spectral data have also been discussed in terms of structural property relationship. The dyeing assessment of all the dyes was evaluated on wool and polyester textile fibers. The dyeing of chrome treated (i.e., chrome mordented) wool and polyesters was also monitored. The results show that a better hue was obtained on mordented fibers. The results of the anti-bacterial properties of the chrome dyes revealed that the toxicity of these dyes against bacteria is fairly good. .
The use of pyridinium fluorochromate (PFC)supported on trisyl silica gel for oxidation reactions
Authors: Aydin Fatma , Turunc Ersan
Published: March 2007

Pyridinium fluorochromate supported on TriSyl silicas was prepared by co-adsorption. The supported reagent was used in equimolar quantity to oxidise some organic compounds with good yields and complete selectivity. These procedures are mild, efficient, safe and the work-ups are very convenient. .
Content of heavy metals in Gentiana lutea L. roots and galenic forms
Authors: Radanovic Dragoja , Antic-Mladenovic Svetlana , Jakovljevic Miodrag , Kresovic Mirjana
Published: March 2007

An experimental field for the cultivated production of Gentiana lutea L. was established five years ago at the Suvobor Mountain, Serbia. Soil analysis of this area revealed the occurrence of high pseudo-total (Ni - 1270 mg/kg, Cr - 423 mg/kg, Co - 385 mg/kg) and available (especially Ni - 133 mg/kg) heavy metals contents in the soil. Hence, the aim of this research was to evaluate the quality of Gentiana lutea L. - roots and galenic forms (liquid extract in 70 % ethanol, spissum and siccum) produced from the roots, because, for most plants, heavy metals accumulate in the root tissue. The amounts of Ni and Cr found in the analyzed roots were very high (54 mg/kg and 14 mg/kg, respectively). The efficiency of ethanol in extracting heavy metals from the roots varied depending on the particular element. The highest efficiency was obtained for Ni (41.3 %), then for Cd (39.5 %), Pb (37.0%) and Co (30.4 %). According to this, a potential hazard exists for humans, if gentian's galenic forms are produced from the raw material with high heavy metals contents. It is concluded that quality control of the raw material must be carried out before further utilization of gentian. .
Application of reactive siloxane prepolymers for the synthesis of thermoplastic poly(ester-siloxane)s and poly(ester-ether-siloxane)s
Authors: Antic Vesna , Vuckovic Marija , Djonlagic Jasna
Published: March 2007

Thermoplastic poly(ester-siloxane)s (TPES) and poly(ester-ether-siloxane) s, (TPEES), based on poly(butylene terephthalate) (PBT) as the hard segment and different siloxane-prepolymers as the soft segments, were prepared. The TPES and TPEES were synthesized by catalyzed two-step transesterification from dimethyl terephthalate, (DMT), 1,4-butanediol, (BD) and a siloxane-prepolymer. Incorporation of dicarboxypropyl- or disilanol-terminated poly(dimethylsiloxane)s (PDMS) into the polar poly(butylene terephthalate) chains resulted in rather inhomogeneous TPES copolymers, which was a consequence of a prononuced phase separation of the polar and non-polar reactants during synthesis. Two concepts were employed to avoid or reduce phase separation: 1) the use of siloxane-containing triblock prepolymers with hydrophilic terminal blocks, such as ethylene oxide (EO), poly(propylene oxide) (PPO) or poly(caprolactone) (PLC) when the terminal blocks serve as a compatibilizer between the extremely non-polar PDMS and the polar DMT and BD, and 2) the use of a high-boiling solvent (1,2,4-trichlorobenzene) during the first phase of the reaction. Homogeneity was significantly improved in the case of copolymers based on PCL-PDMS-PCL. .
Relationship and discrepancies between the Extended-Rydberg and the Generalized Buckingham potential energy functions
Authors: Lim Teik-Cheng
Published: March 2007

This paper relates the interatomic energy according to the Extended-Rydberg and the Generalized Buckingham potential functions by applying a Maclaurin series expansion on the latter and thereafter comparing it with the former. In so doing, the plotted curves of these two functions not only show equal curvature at the equilibrium state, but also reveal a discrepancy for the finite distortion. It is shown that, when equated at equilibrium, the Generalized Buckingham gives a lower energy in comparison to the Extended-Rydberg at finite bond compression and stretching. However, the energy difference diminishes when the interatomic distance exceeds twice that at equilibrium. Due to such discrepancies upon comparative normalization, it would be beneficial for computational chemists to select the appropriate potential function for the purpose of conservative molecular modeling. .
Effect of glassy carbon properties on the electrochemical deposition of platinum nano-catalyst and its activity for methanol oxidation
Authors: Terzic Sanja , Tripkovic Dusan , Jovanovic Vladislava , Tripkovic Amalija , Kowal Andrzej
Published: March 2007

The effects of the properties of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on glassy carbon (GC/Pt) for methanol oxidation in alkaline and acidic solutions were studied. Platinum was potentiostatically deposited on two glassy carbon samples, thermally treated at different temperatures, which were either polished or anodicaly polarised in acid (GCOX-AC/Pt) and in alkali (GCOX-AL/Pt). Anodic polarisation of glassy carbon, either in alkaline or acidic solution, enhances the activity of both types of GC/Pt electrodes for methanol oxidation. The activity of the catalysts follows the change in the properties of the glassy carbon support upon anodic treatment. The specific activity of the GCOX-AL/Pt electrode for this reaction in alkali is increased only a few times in comparison with the activity of the GC/Pt one. On the other hand, the specific activity of the GCOX-AC/Pt electrode for methanol oxidation in acid is about one order of magnitude higher than that of the GC/Pt electrode. The role of the substrate on the properties of catalyst is discussed in detail. .
Summertime PAH assembly in Mediterranean air: The Herceg Novi sampling station as an example
Authors: Jovanovic Vladimir , Pfendt Petar , Jovanovic Anka
Published: March 2007

The results of an analysis of the total suspended particles (TSP), total solvent organic extracts (TSOE), and polycyclic aromatic hydrocarbons (PAHs) in aerosol samples collected from the atmosphere of Herceg Novi from 17th June to 15th September in 1998 and 1999 are presented. The TSP and TSOE concentrations were determined by the standard gravimetric method, whereas the PAHs from the organic part of the aerosol were analyzed by the GC-MS method. The difference found in the TSP and TSOE contents between the two consecutive years (before and after the bombing of Yugoslavia) was attributed to changes in the intensity and origin of emissions from dominant sources, specific to the summer period of this region. The content and nature of the PAHs identified in the samples of 1998 and 1999 were also different, indicating the significance of traffic as the source of PAHs, which was of significantly lower intensity in 1999 (immediately after the war) due to the lower influx of tourists. Factor analysis showed that the PAH distribution at the measuring site in 1999 was largely determined by meteorological parameters, mainly by the average daily temperature and wind direction. In 1998, the dominant impact on the PAH distribution was attributed to traffic, both local and from a wider region, without an explicit impact of meteorological parameters. .
Restoring dignity and respect to health care workers
Authors: Nedic Olesja
Published: March 2007

Introduction. This year, the World Health Organization focuses on restoring dignity and respect to health care workers. The aim of this study was to investigate the workplace stressors in physicians. Material and Methods. The present study was performed in the period 2002-2004, among physicians treated in the Health Center Novi Sad. The examinees were asked to fill out a questionnaire - a workplace survey - to identify workplace stressors by using a self-evaluation method. The physicians were divided into three groups: those practicing surgery (S), internal medicine (IM) and preventive-diagnostics (PD). Statistical analysis was done using SPSS and STATISTICA software. The sample included 208 physicians with an average age of 40 years (SD=7,1); average work experience of 22 years (SD=8,1). Results. 65 physicians from group S and 108 physicians from group IM, identified the following workplace stressors: treating patients in life-threatening situations (47.7%, 30.6%, respectfully); on-call duty (13.8%, 12%); low salary (10.8%, 10.2%); limited diagnostic and therapeutic resources in the IM group. 35 physicians from the DP group identified the following stressors: low salary (25%), treating patients in life-threatening situations and a great number of patients (16%). The analysis of all examined physicians revealed the following workplace stressors: treating patients in life-threatening situations (34.6%), low salary (13%), on-call duty and overtime, and too many patients per physician (11.5%). Conclusion. Restoring the reputation of health workers can be done by providing new equipment to resolve life-threatening situations, by increasing salaries, reducing on-call time, as well as the number of patients. Generally speaking, this should help to improve the quality of work in the health care system, in accordance with the recommendations of the WHO. .
Echocardiographic evaluation of left ventricular morphology and function in active sportsmen
Authors: Vujin Bojan , Benc Dragan , Grujic Nikola , Srdic Svetozar , Radisic Biljana , Kovac Marko
Published: March 2007

Introduction. Echocardiography is a noninvasive, reliable method for evaluation of left ventricular morphology and function. Judo and wrestling are sports characterized by intensive and high physical and isometric effort, while football is characterized by long-term physical isotonic effort. The key compensatory mechanism with both groups of sportsmen is left ventricular hypertrophy. The aim of this study is evaluate left ventricular morphology and function in a group of judo players, wrestlers and football players during competition season and their interactive comparation. Material and Methods. 42 judo players and wrestlers and 43 football players were examined. Results. An increase in thickness of the septum and posterior wall was established in both groups of sportsmen, but the thickness was statistically more significant in judo players. On the other hand, in football players, a statistically significant left ventricular end-diastolic volume index enlargement was found, compared to reference values and compared to end-diastolic volume index in judo players and wrestlers. High left ventricular ejection fraction was established in both groups, but it was statistically significantly higher in football players. Left ventricular mass index was statistically increased in both groups, but it was higher in judo players and wrestlers.
Monitoring of neurological parameters in newborns with hypoxic-ischemic encephalopathy
Authors: Djindjic Jasmina , Obradovic Slobodan
Published: March 2007

Asphyxia i a condition caused by lack of oxygen in tissues and organs. The basic pathogenic mechanisms of asphyxia are: 1)hypoxemia, 2) ischemia. The effects of perinatal asphyxia on the brain of a neonatal baby are critical in development of hypoxic-ischemic encephalopathy. The diagnosis of hypoxic-ischemic encephalopathy is based on clinical data including course of pregnancy and delivery (Apgar score) and especially on the neurological status of the newborn (consciousness, tonus, convulsions, reflexes, vegetative functions, etc.) and it can be confirmed by biochemical analysis and neurological examinations. The aim of this paper is to determine the importance of prenatal and perinatal risk factors for hypoxic-ischemic encephalopathy, as well as their effects on the development of neurological complications and further neurological problems. The research included 148 newborn infants born in the period from January 1, 1996 to January 1, 1999, with gestational age of 27 to 42 weeks, with hypoxic ischemic lesions of the central nervosus system. The control group included 58 children of the same age and the same gestation, with generalized hypotonia ("floppy infant") but without any signs of hypoxic ischemic lesions of the central nervous system. In the group of examined newborn infants with hypoxic ischemic lesions, from 149 children 1 (0.67%) died, 87 (53.89%) had normal findings, whereas the handicap was established in 61 (40.94%). Perinatal asphyxia affects the fetus and newborn infants not by individual factors, but with at least three or four associated factors. The disorders caused by asphyxia are in inverse proportion to the duration and intensity of hypoxic insults and the gestational age of the newborn. .
The role of insulin analogues in the current treatment of diabetes mellitus
Authors: Mitrovic Milena , Pantelinac Pavle , Radosavljevic Jovanka , Bajkin Ivana , Todorovic-Djilas Ljiljana
Published: March 2007

Introduction. Ever since insulin was discovered by Banting and Best in 1921, all further researches in this field had been conducted with one goal: to find new insulin molecules which would provide better glycemic control with fewer side effects i.e. to mimic endogenous physiological insulin secretion. Normal insulin secretion. In healthy individuals, endogenous insulin secretion can be classified as basal (which provides basal glucose homeostasis) and stimulated (as a response to a meal). Conventional insulin preparations - human insulin, have time-action profiles that cannot fully imitate endogenous insulin secretion, thus leading to postprandial hyperglicemia and high glycemic oscilations during the day. Rapid-acting analogues. Rapid acting analogues should have a time-action profile with onset of less than one hour, duration less than four hours, hypoglycemic potency equal or greater than that of human insulin, and similar effects in all patients. Two rapid action analouges, lispro and aspart are available. Basal insulin analogues. The ideal basal insulin should provide slow and constant absorption, long half-life that would provide once daily dosing (or every other day), and peakless effect. Insulin glargine led to solubility at pH 4 and to slow absorption in neutral pH environment. Insulin detemir is a soluble insulin analogue with neutral pH and affinity to bind to serum albumin, thus gaining prolonged action. Mitogenic influence. The mitogenic influence of insulin is due to the affinity to bind to IGF-1 receptors. Following two-year administration of glargine in mice and rats, systemic carcinogenic potential was not found, though there were reports of hepatocellular carcinomas, which are frequently found in these animals. Conclusion. In the last two decades, many trials have shown that unsatisfactory glycemic control leads to chronic complications in both types of diabetes. Using basal glucose level, postprandial glycemy and HbA1c as matabolic parameters, it has been proven that only strict glycemic control can lower the risk of developing complications. Discovery of insulin analogues (both rapid acting and basal) enables physicians to provide better glycoregulation and less hypoglycemic incidents to their patients. .