Wyniki wyszukiwania - Biblioteka Nauki

1

Selective catalytic reduction of NO over Ag/Al2O3 catalyst.

100%

Darkowski A.

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tom Vol. 10, nr 57

445-450

EN

The reduction of NO by propene, in the presence of oxygen, over Ag/Al2O3 was studied. The catalyst was prepared by anodic oxidation of aluminum foil in sulfuric acid solution. The alumina films contain parallel cylindrical pores of uniform diameter. Silver was electrodeposited on the bottom of the pores. Oxidized foil was used for preparation of a catalytic reactor. The catalytic activity was tested in a flow reactor. The dependence of nitrogen oxide and propane concentration on the temperature of the catalytic reactor shows that between 300 and 450 conversion of nitrogen oxide is over 0.8.

2

(alfa, beta) reduction of decision table : a rough approach

80%

Shrabonti G. , Ranjit B. , Alam S. S.

|

2001

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tom Vol. 26, No. 4

273-281

EN

In this paper, we generalise Pawlak's rough approach for simplifying a decision table in an information system. We consider an information system where attribute values are not always quantitative, rather subjective having vague or imprecise meanings. Some objects may have attribute values which are almost identical, i.e., they can't be distinguished clearly by the attributes. Considering this observation, we present a generalised method for reduction of decision table for different choice values of alfa and beta, a being for condition attributes and beta for decision attributes where Alfa, Beta € [0, 1]. For a = 1 and Beta = 1, the method reduces to Pawlak's method.

3

Method for efficient distribution of means to reduce CO2 emissions in a set of power plants

80%

KAŁUSZKO A.

Operations Research and Decisions

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2013

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tom 23

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nr 2

55-65

EN

A method for the allocation of technologies of reduction of CO2 emission to sources of emissions based on dynamic programming has been described. The purpose of the application of the method was to develop an efficient strategy of allocating financial means for reducing CO2 emissions from a set of coal and lignite fired power plants (carbon dioxide sources) which enables reduction of the total emissions to the required level within a given time horizon, at the minimum cost. The application of the method is illustrated based on the set of the 20 largest Polish coal and lignite fired power plants.

4

Reduction of NO by C3H6 over MgF2-supported copper-manganese oxide catalysts in the presence of H2O.

80%

Wojciechowska M. , Zieliński M. , Malczewska A.

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tom Vol. 10, nr 57

421-426

EN

The study has been undertaken to establish the effect of steam on the activity of copper oxides or manganese oxides supported on MgF2 in the reaction of NO + C3H6 + O2. The results were compared with those obtained for similar catalysts supported on commonly used g-Al2O3. For the systems with copper and manganese oxides, a decrease in the activity was noted after introduction of steam to the reaction mixt. The catalyst CuOxMnOx/MgF2 was found more resistant to steam (a ~ 15% decrease in activity) than CuOxMnOx/g-Al2O3 (~30% decrease in activity).

5

Unambiguous Functions in Logarithmic Space

80%

Herman G. , Soltys M.

|

2012

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tom Vol. 114, nr 2

129-147

EN

We investigate different variants of unambiguity in the context of computingmulti-valued functions. We propose a modification to the standard computation models of Turing machines and configuration graphs, which allows for unambiguity-preserving composition. We define a notion of reductions (based on function composition), which allows nondeterminism but controls its level of ambiguity. In light of this framework we establish reductions between different variants of path counting problems. We obtain improvements of results related to inductive counting.

6

Reduction of Singular 2D Models to Equivalent Standard Models

80%

Kaczorek T.

|

1999

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tom Vol. 47, nr 2

141-151

EN

A new extended Roesser type model is introduced. It is shown that: 1. Any singular 2D general model (1) with [formula] can be reduced to the model (6) or (6'), 2. Regular singular 2D model (9) can be reduced to standard extended Roesser type model (11) if its pencil is regular. Sufficient conditions are established under which a singular 2D general model (1) can be reduced to standard models of the form (28) or (35).

7

Multisequential Grammars with Homogeneous Selectors

80%

Meduna A. , Vurm P.

|

2001

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tom Vol. 48, nr 1

55-60

EN

This paper deals with selective substitution grammars. It concentrates on multisequential grammars with homogeneous selectors that have all their activated parts identical. The present paper reduces the number and size of selectors in these grammars. Indeed, it demonstrates that for every phrase-structure grammar, there exists an equivalent multisequential grammar having two homogeneous selectors, either of which has only two activated parts.

8

A Rough Set Approach to Multiple Classifier Systems

80%

Suraj Z. , El Gayar N. , Delimata P.

|

2006

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tom Vol. 72, nr 1-3

393-406

EN

During the past decade methods of multiple classifier systems have been developed as a practical and effective solution for a variety of challenging applications. A wide number of techniques and methodologies for combining classifiers have been proposed in the past years in literature. In our work we present a new approach to multiple classifier systems using rough sets to construct classifier ensembles. Rough set methods provide us with various useful techniques of data classification. In the paper, we also present a method of reduction of the data set with the use of multiple classifiers. Reduction of the data set is performed on attributes and allows to decrease the number of conditional attributes in the decision table. Our method helps to decrease the number of conditional attributes of the data with a small loss on classification accuracy.

9

Probing palladium-silica interactions in Pd/SiO2 catalysts subjected to high temperature reduction

70%

Łomot D.

|

1998

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tom Vol. 72, nr 12

2598-2605

EN

Metal-support interactions in silica-supported palladium catalyst have been re-investigated. In addition to the already recognized model reaction of 2,2-dimethylpropane with hydrogen, where the isomerization selectivity appears as a useful indication in diagnosing changes in the catalyst, another effective probe has been used: a variable capability of differently modified palladium to form the hydride phase. High temperature reduction at 600 degree C of 1.6 wt% Pd/SiO2 results in the formation of palladium silicide. However, the prove of this fact by X-ray diffraction is ambiguous or impossible, because of a low content of highly dispersed Pd-containing phase. On the other hand, the formation (stability) of Pd hydride provides an interesting diagnostic tool: Pd/SiO2 transformed into Pd silicide does not form the metal hydride phase. The stability of the Pd hydride phase and the catalytic conversion of 2,2-dimethylpropane are complementary methods is probing silica-supported palladium catalysts.

10

Reduction of NO using Mn(4+) and Fe(3+) - impregnated active carbon

70%

Grzybek T. , Buczek B.

|

1998

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tom Vol. 72, nr 3

607-612

EN

Carbonaceous materials were promoted by consecutive impregnation with manganese salt (potassium permanganate with or without the addition of sulphuric acid) and iron salt. Texture of the materials obtained was studied by low temperature argon sorption and manganese and iron distribution by X-ray photoelectron spectroscopy. The influence of impregnating solution on the structure of the catalysts studied was discussed. Catalytic properties (activity and selectivity) in selective catalytic reduction of nitric oxide with ammonia of doubly promoted carbonaceous material were compared with iron or manganese-containing active carbon.

11

The use of the new magnesium-derived hydride reagen for carbohydrate derivatives

70%

Szabovik G. , Medgyes A. , Antal Z. , Varga Z. , Knott W. , Liptak A.

|

1999

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tom vol. 73 nr 6

1003-1009

EN

The magnesium hydride based reagent in THF solution is an excellent tool for the stereoselective reduction of different uloside derivatives. Sugar azides, sulfonyl esters give aminosugars and methylose derivatives without affecting other functionalities. Halogenated sugars or methylene derivatives are stable under these conditions. The reagent can be applied in the presence of a wide variety of blocking groups (acetals, benzyl and allyl ethers, imides, C=C bonds) generally used in the carbohydrate chemistry.

12

New porous iron electrode for hydrogen evolution - production and properties

60%

Jaron A. , Żurek Z.

|

2008

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tom Vol. 53, iss. 3

847-853

EN

A new method of fabrication of porous iron electrodc is presented. In due of growing interest for hydrogen production by use of electrochemical technology, the extensively research of new cheaper electrode materiał currently are lead. At present production of industrial porous metal electrodes is mainly based on fabrication nickel HSE (high surface area) electrodes by sintering of nickel powder in oxygen less atmosphere or etching of Raney alloy to Ni-Raney electrodes. We proposed to use cheaper porous iron electrodes produced from iron powder instead of the expansive nickel ones. An inexpensive method of production is based on successive oxidation and reduction of the iron powder bed. This work deals with kinetics of oxidation at 400 and 600°C of iron powder bed in air and water vapor. Thermal effect during oxidation process was determined by DTA/TG analysis. Reduction process of porous oxidized precursor in hydrogen at 600° C was also studied. The surface morphology of the porous oxidized precursor as well as the received porous metallic iron structure were examined by SEM. The chemical composition was determined by SEM/EDX and XRD analysis. The optimal condition (i.e. time, temperaturę) for fabrication process of iron porous electrode with highest specific surface area and open porosity was appointed. The electrochemical properties of porous iron electrodes (obtained in different conditions of oxidation process) were examined by potentiodynamic measurement. The current-potential dependence was obtained in IM KOH at 70°C vs. Hg—HgO reference electrode i.e. in conditions corresponding with industrial process of hydrogen production. Hydrogen evolution reaction on iron in conditions mentioned above is considering with the Volmer-Heyrovsky-Tafel kinetic mechanisms. For porous electrode and bulk sample iron and nickel electrodes the E100 potential corresponding for evolution of hydrogen with current density 1000 A/m2 was determined. E100 potential is assuming values from -1.24 to -1.32 V (depends of sample history) for porous iron electrodes. This potential for bulk iron electrode (-2.96V) and nickel (-1.50V) is significantly higher.

PL

W dobie poszukiwania nowych materiałów o rozwiniętej powierzchni stosowanych w elektrochemicznej produkcji gazów oraz jako nośniki katalizatorów jednym z podstawowych czynników decydujących o ich przydatności jest koszt wytworzenia. Obecnie porowate elektrody przeznaczone do zastosowania w elektrochemii i katalizie przemysłowej otrzymuje się na drodze spiekania proszków metalicznych z podłożem metalicznym lub rozwija się powierzchnię metalu na drodze trawienia np. nikiel Raney'a. W prezentowanym artykule przedstawiano korzystniejszy ekonomicznie sposób wytwarzania porowatych elektrod żelaznych w procesie sekwencyjnego utleniania i redukcji. W pracy przedstawiono badania kinetyki utleniania proszku żelaza w temperaturze 400 i 600°C w atmosferze powietrza i pary wodnej. Efekty termiczne w czasie procesu utleniania zostały określone na drodze analizy DTA/TG. Badania procesu redukcji porowatego prekursora tlenkowego prowadzono w temperaturze 600°C w atmosferze wodoru. Wykonano badania morfologii (SEM) dla otrzymanych spieków tlenkowych jak i porowatych struktur metalicznych otrzymanych w wyniku procesu redukcji. Skład próbek określono przy pomocy analizy SEM/EDX i XRD. Na podstawie przeprowadzonych badań wyznaczono optymalne warunki (czas, temperatura) procesu wytwarzania porowatej elektrody żelaznej o wysoce rozwiniętej powierzchni właściwej oraz zaproponowano mechanizm utleniani złoża proszku żelaza. Właściwości elektrochemiczne wytworzonych elektrod oceniono na drodze badań potencjodynamicznych. Zależność prąd-napięcie mierzono w IM KOH względem elektrody odniesienia Hg—HgO w temperaturze 70°C - w warunkach odpowiadających przemysłowym warunkom otrzymywania wodoru. Mechanizm kinetyki wydzielania wodoru w/w warunkach odpowiada mechanizmowi wg Volmera-Heyrovskyego-Tafela. Dla porowatych elektrod żelaznych oraz próbek żelaznych i niklowych o gładkiej powierzchni wyznaczono potencjał E100 odpowiadający wydzielaniu wodoru prądem o gęstości 1000A/m2. Potencjał dla porowatych elektrod żelaznych E100 przyjmował wartości od -1.24 do -1.32 V w zależności od warunków otrzymywania elektrody. Potencjał ten dla elektrody żelaznej (-2.96 V) i elektrody niklowej (-1.50 V) o gładkiej powierzchni jest znacząco wyższy.

13

Ograniczanie trwałych zanieczyszczeń organicznych (TZO) z procesów przemysłowych

60%

Burchart-Korol D.

|

2009

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tom R. 13, nr 4

181-184

PL

Przedstawiono problem emisji trwałych zanieczyszczeń organicznych (TZO) w przedsiębiorstwach przemysłowych. Najgroźniejszymi TZO tworzonymi i uwalnianymi w sposób niezamierzony z procesów termicznych z udziałem substancji organicznych i chloru w wyniku niepełnego spalania lub reakcji chemicznych są: polichlorowane dibenzo-p-dioksyny i polichlorowane dibenzofurany (PCDD/PCDF), polichlorowane bifenyle (PCB) oraz heksachlorobenzen (HCB). Dostosowanie do surowych norm emisji obowiązujących w Unii Europejskiej jest jednym z głównych wyzwań dla przemysłu krajowego. W najbliższej przyszłości koniecznością staną się badania emisji TZO w polskich przedsiębiorstwach. Przedstawiono w artykule scenariusze BAU+Climate oraz MFTR opracowane dla emisji PCDD/PCDF i PCB. Jako studium przypadku posłużono się sektorem hutnictwa żelaza i stali, w którym przedstawiono możliwości ograniczenia TZO oraz scenariusze tych emisji. Procesy termiczne w przemyśle stalowym powodują wysoki poziom TZO, a szczególnie PCDD/PCDF do środowiska.

EN

The work is presents persistent organic pollutants (POPs) emit from industrial enterprises. Adaptation to the European Union emission standards is the main challenge for national industry. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) belong to POPs unintentionally formed and released from thermal processes involving organic matter and chlorine as a result of incomplete combustion or chemical reactions. In the nearest future investigations of POPs emission in Polish enterprises will be necessity. In this work it was presented two emission scenarios for pollutants to year 2020: BAU+Climate scenario (Business as Usual with Climate Policies) and MFTR scenario (Maximum Feasible Technical Reduction) for PCDDs/PCDFs and PCBs. It was shown POPs reduction and emission scenarios from iron and steel production as a case study. Steel industry causes high level of POPs, particularly PCDDs/PCDFs.

14

Eesti keele luhikeste klusiilide haalduse variatsioon ja seda mojutavad tegurid

60%

Ermus L.

Mäetagused

|

2017

|

tom 68

27-52

EN

Plosives in Estonian have been considered voiceless. However, analysis has shown that short plosives tend to get at least partially voiced and otherwise reduced in connected speech. This seems to be quite a universal tendency in different languages. The present paper investigates short plosives in intervocalic position in most frequent content words. Phonetic materials were extracted from the Phonetic Corpus of Estonian Spontaneous Speech. Patterns in the reduction of plosives and possible influences of stress and vowel context were investigated. Two kinds of allophones emerged – those that were fully realised and had a distinguishable release burst, and the reduced ones that had lost the burst phase. The amount of reduced tokens differentiated the velar plosive [k] from others. As [p] and [t] both had over 65% of fully realised tokens, but over 60% of [k] tokens were reduced. [k] also had most different allophones. Among fully realised tokens there were voiceless, partially voiced, and fully voiced allophones. The voiceless allophone was the rarest, 19% tokens of [p] and only 10% of [t] and [k] were voiceless. Most frequent allophones among phonemes were partially voiced for [p] (29%), fully voiced for [t] (37%), and reduced voiced for [k] (47%). Closure durations were related to place of articulation. [p] had the longest average durations and [t] the shortest. Across all tokens [k] and [t] had similar average durations but within allophones durations were closer between [k] and [p]. Burst durations were the longest, around 30 ms for [k] and almost the same duration, between 21–23 ms, for [p] and [t], with the exception of the voiceless allophone [t], which was 27 ms. Closure durations differed significantly between [p] and [t] and burst durations were significantly different between [k] and other phonemes. Stressed positions included both lexical and contrastive stresses. Stress had some effect on the allophonic distribution but almost none on durations. As expected, there were more voiceless and partially voiced tokens in stressed position and more reduced tokens and total loss in unstressed position. Differences were the biggest for [t] and the smallest for [k]. Durations differed very little, whereas none were statistically significant. Vowel context had some influence on allophonic distribution. The influence was the biggest on [t]. Overall, there were more fricative and approximant tokens around [i].[t] had more partially voiced tokens and less voiced tokens around labial vowels [o, u]. There were more reduced [k] tokens around [a] and [i]. On durations the vowel context again influenced [t] the most. Durations between all vowel contexts were statistically different for [t] (p<.01); the longest durations appeared after [i]. In general, the present study confirms the results of the previous ones. Allophonic distribution is very similar to the previous study of Estonian spontaneous speech. Closures were at least partially voiced in most cases which refer to carry-over voicing of the previous vowel. Vocal cord vibration stops for a very brief time or does not stop at all during short closure times. Burst durations appear to be longer in spontaneous speech than in read speech. Little influence of stress is in accordance with findings in the studies on Estonian and some other languages. Vowel influences were dependent on the place of articulation. Bilabial [p] was the least affected both in allophonic variation and in durations. Velar [k] was influenced by the vowel context but it mostly occurred in whole as extensive reduction; different vowels had more effect on the allophonic variation than in the case of [p] but durations were almost unaffected. Influences on [t] mostly occurred as significant duration differences; yet, also some differences in allophonic variation occurred.

15

Kinetyka redukcji Fe(III) edta roztworami ditioninu sodowego

60%

Mathews B. , Suchecki T. T.

|

2002

|

tom Vol. 28, no. 3

21-31

PL

Badano szybkość redukcji Fe(III)edta przez ditionin sodowy, Na(2)S(2)O(4) w zależności od: stosunku początkowych stężeń reagentów [Na(2)S(2)0(4)]o/[Fe(III)edta]o = 0,1:1; 0,3:1; 0,5:1 oraz 0,7:1, temperatury - 20, 40, 60, 80°C, pH roztworu - 3, 5, 7, 9 i początkowego stężenia chelatu żelazowego [Fe(III)edta]o = 0,005; 0,010; 0,050 i 0,100 mol/dm3. Pomiary prowadzono w okresowym reaktorze szklanym o pojemności 300 cm3. Stężenie jonów żelaza(III) oznaczano spektrofotometryczną metodą ortofenantrolinową. Wszystkie pomiary miały analogiczny przebieg - następowała bardzo szybka redukcja jonów żelaza(lll) w początkowych sekundach procesu, do poziomu zależnego jedynie od stosunku początkowych stężeń reagentów. Dla [Na(2)S(2)0(4)]o/[Fe(III)edta]o = 0,7:1 uzyskano całkowitą redukcję Fe(III)edta do Fe(II)edta. Pozostałe przebadane parametry nie miały wpływu na szybkość procesu redukcji

EN

The rate of Fe(III)edta reduction by sodium dithionite was investigated according to: ratio of initial reagents concentrations, [Na(2)S(2)0(4)]o/[Fe(III)edta]0 = 0.1:1; 0.3:1; 0.5:1 and 0.7:1, temperature - 20, 40, 60 and 80°C, solution pH -3,5,1 and 9, initial concentration of ferric chelate, [Fe(III)edta]0 = 0.005; 0.010; 0.050 and 0.100 mol/dm3. A periodic glass reactor of 300 cm3 volume was used. Concentrations of ferrous ions were determinated by o-fenanthroline method. Ali runs had the similar character. Ferric ions were reduced during first few seconds to a level depended from the initial ratio of reagents concentrations. Only for, [Na(2)S(2)0(4)]o/[Fe(III)edta]o = 0.7:1 run, Fe(III)edta was completely reduced to Fe(III)edta. Other investigated parameters had no influence on the Fe(II)edta process

16

Europa 2050 – mapa drogowa do energetyki niskowęglowej

60%

Malko J.

|

2010

|

tom R. 86, nr 8

176-181

PL

W roku 2009 Rada Europejska ogłosiła cel redukcji emisji gazów cieplarnianych na poziomie nie niższym niż 80% w odniesieniu do roku 1990. „Roadmap 2050” jest studium ustalającym podstawowe fakty i implikacje dla przemysłu europejskiego, a zwłaszcza dla sektora elektroenergetycznego. Celem studium jest sprecyzowanie praktycznych, niezależnych i obiektywnych ścieżek dojścia do założonego poziomu emisyjnego w zakresie emisji gazów cieplarnianych. W artykule przedstawiono podstawowe tezy i wnioski studium „Roadmap 2050”.

EN

Last year the European Council announced an objective to reduce green-house gas emission by at least 80% below 1990 levels by 2050. “Roadmap 2050” is a study to establish a fact base behind this goal and derive the implication for European industry particularly in the power sector. A mission of this study is to provide a practical independent and objective pathways to achieve prescribed target of GHG emissions. In the paper basic thesis and conclusions of “Roadmap 2050” are presented.

17

Requirements on cognition-oriented risk analysis instruments cognitive effects during the risk analysis process and their reduction

60%

Jonen A.

|

2009

|

tom Spec. ed.

136-154

EN

When analysing risks, it is time and again necessary to assess subjectively the parameters of the risk situation (e.g. project, process), especially when statistical data are lacking. For the person in charge, quantifying the different risk weights and dimensions using relative numbers (percentage) is difficult. Problems with statistical methods and heuristics partially derive from the individual character of the person or the special risk situation. Besides these cognitive aspects, the transparency of the risk analysis process is often criticized. The objective of this article is on one hand to describe different cognitive effects that occur during the process of risk analysis and on the other hand to show approaches how negative cognitive effects can be overcome. Therefore first the different cognitive effects are described on a general level (chapter 2). In a second step it is shown how these effects influence the analysis of risks (chapter 3). Finally, ways are shown how the influence of the different effects concerning the risk analysis could be reduced (chapter 3). Concluding with a summary the results and fields for further research are shown (chapter 4).

18

One-pot synthesis of(R)-convolutamydineA involvingin situchiral organocatalyst formation

60%

Wei S. , Schmid B. , Macaev F. Z. , Curlat S. N. , 1 , Malkov A. V. , Tsogoeva S. B.

Asymmetric Catalysis

|

2015

|

tom 2

|

nr 1

EN

The application of a convenient one-pot synthetic strategy, utilizing an in situ formed organocatalyst, to the enantioselective synthesis of anti-leukaemia agent (R)-convolutamydine A has been demonstrated.

19

Fast spectrophotometric method for determination of nitrate and nitrite using diphenylamine-4-sulfonic acid

60%

Mroczkowski W. , Stuczyński T.

|

2009

|

tom Vol. 54, No. 4

753-759

EN

A new method for determination of nitrates was developed. It was based on reduction of to nitrates to nitrites using 0.1%diphenylamine-4-sulfonic acid solution in 95%(m/m) H,SO4. Nitrites obtained in this reaction were diazotized using sulfanilic acid and then coupled to N-( 1 -naphtyl)-ethylenediamine to form a coloured azo complex, which was determined spectrophotometrically at the wavelength of 550 nm. Calibration plot was linear in nitrate concentration range 1-20 μg mL-1 N with R2 = 0.99.

PL

Opracowano nową metodę oznaczania azotanów. W metodzie tej kwas difenyloamino-4--sulfonowy redukuje azotany(V) do azotanów(III) w środowisku stężonego H2SO2. Otrzymane azotyny poddaje się reakcji diazowania z kwasem sulfanilowym i sprzęgania z N-l-naftylo-etylenodiaminą(zmodyfikowana metoda Griessa-Ilosvaya) w celu otrzymania barwnika azowego. Absorbancję roztworu otrzymanego barwnika mierzy się spektrofoto-metrycznie przy długości fali 550 nm. Liniową zależność kalibracyjną (R2 = 0,99) uzyskano w zakresie stężeń azotanow(V): 1-20 μg mL-1.

20

Katalizowane enzymami reakcje estryfikacji i redukcji - otrzymywanie optycznie czynnych alkoholi

60%

Plenkiewicz J.

|

2000

|

tom Vol. 26, z. 2

19-29

PL

Przedstawiono kierunki badań prowadzonych w Zakładzie Technologii i Biotechnologii Środków Leczniczych, których celem było otrzymanie optycznie czynnych alkoholi, posiadających drugą reaktywną chemicznie grupę funkcyjną. Jako chiralne katalizatory wykorzystano izolowane enzymy oraz cale komórki drożdżowe (Saccharomyces cerevisiae). Otrzymane optycznie czynne związki mogą być wykorzystane jako chiralne syntony w dalszych syntezach, prowadzących do otrzymania leków lub pestycydów, lub jako pomocniki chiralne w asymetrycznej syntezie.

EN

The main directions of the investigations carried out in the Department of Drugs Technology and Biotechnology, aimed at the preparation of optically active alcohols with second reactive substituent, are presented. Isolated enzymes as well as whole yeast cells (Saccharomyces cerevisiae) were used as the chiral catalysts. The obtained optically active compounds can be used as chiral synthons in further syntheses leading to biologically active substances or as chiral auxiliaries in an asymmetric synthesis.