Performance during post-harvest storage of banana cv. 'prata', 'maçã' and 'nanica' exposed to physical and chemical treatments

Banana is the most consumed fruit in the world and Brazil is the second largest producer. Despite its global position, Brazil has an average of 40% losses during the post-harvest period. So, this experiment aimed at evaluating the efficiency of post-harvest treatments to improve the storage of banana cultivars cv. 'Prata', 'Maçã' and 'Nanica'. The fruits were acquired at CEASA with green peel, and were submitted to six different treatments: T- immersion in drinking water for 3 minutes (control), H3 - hot water (50 °C for 3 minutes), H8 - hot water (50 °C for 8 minutes), HP - immersion in hypochlorite 0.2% for 3 minutes, OS - immersion in soybean oil 10% for 3 minutes, and OM - immersion in mineral oil 10% for 3 minutes. The fruits were stored at room temperature at about 21 °C for 14 days and evaluated in three periods (1, 7 and 14 days) comparing peel color, flesh/peel ratio, titratable acidity (TA), soluble solids (SS), SS/TA ratio, and pH. The fruits of cv. 'Prata' and 'Maçã' submitted to the treatments H3, H8 and HP ripened at the same time as the control for peel color, which showed increased soluble solids, flesh/peel ratio, acidity and a decrease in pH. On the other hand, the cv. 'Nanica' did not respond significantly different when compared to the applied treatments and the control. The fruits treated with OM and OS were kept green for a longer time for the cultivars 'Prata' and 'Nanica', but there were some changes on peel color due dark spots in 'Prata' banana and a softening aspect in 'Nanica', indicating some level of toxicity of these treatments. Fruits of the 'Maçã' cultivar continued green with the application of mineral oil, without toxicity symptoms. In conclusion, the treatments applied did not show any advantage for storage of these fruits.

Poultry carcass decomposition and physicochemical analysis of compounds in different Composter types

This study aimed to assess five composter types in poultry carcasses decomposition and to perform a physicochemical analysis of the compounds obtained. Composter types used were six-hole brick, wood, screen, windrow with three PVC pipes with six holes and windrow with three PVC pipes with 10 holes. Composting was followed by four periods using wood shaving like substrate with one bird carcass placed in each composter. Pile turning was performed every 10 days and temperature in each layer was measured on 1st, 7th, 14th, 19th and 29th day, at 3 p.m., as well as room temperature. Temperature during pile turning was also measured at five points per layer and carcass weighing performed to calculate decomposition percentage. Physicochemical parameters evaluated in substrates were moisture, ash, phosphorus, potassium, nitrogen, pH, organic carbon and C/N ratio, up to 30 days. Data were analyzed by repeated measures model, using MIXED method of SAS software. All values of final physicochemical composition of substrates were found according to values of IN-25, except nitrogen. The composter types were efficient in decomposition of poultry carcasses.

Color change and quality response of ‘lane late’ orange submitted to degreening process

This study aimed at evaluating the effects of ethylene on peel color and compositional changes in ‘Lane late’ orange stored under refrigerated and ambient conditions. Physiologically mature, but green-peeled, oranges were exposed to ethylene gas under room temperature and high relative humidity for 24 hours. Storage chamber was ventilated with fresh air after 12 hours to mitigate consequences derived from fruit respiration. Both nondestructive analysis, such as peel color (hue angle, chromaticity, and brightness) and weight loss, and destructive ones (soluble solids, titratable acidity, pH, soluble solids to acidity ratio, and puncture force) were performed upon harvest, after degreening, and every three days during eighteen days in storage. Experiment was carried out using an entirely randomized design with thirty replications for nondestructive and four replications for destructive analyses, in a split plot scheme. Exposure to ethylene ensured a golden yellow peel for both fruit stored under ambient and refrigerated conditions. High relative humidity, associated with low temperature prevented fruit from losing moisture. Fruit exposure to ethylene did not affect weight loss, soluble solids, titratable acidity, pH, soluble solids, acidity ratio, or puncture force.

Nikkelin, koboltin, lyijyn ja sinkin selektiivinen erottaminen ioninleimaustekniikalla syntetisoiduilla kelatoivilla erotusmateriaaleilla

Kelatoivat erotusmateriaalit ovat osoittautuneet lupaaviksi haitallisten metallien erottamiseksi vedestä. Puhdistettava vesiliuos sisältää vain harvoin pelkästään erotettavaksi tarkoitettuja metallikationeja, sillä useimmiten mukana on erotusmateriaalien tehokkuutta heikentäviä kationeja. Parantamalla erotusmateriaalin selektiivisyyttä voitaisiin häiritsevien ionien vaikutusta vähentää selvästi. Kandidaatintyön tavoitteena oli tutkia ioninleimaustekniikan avulla syntetisoitujen kelatoivien erotusmateriaalien selektiivisyyttä nikkelille, koboltille, lyijylle ja sinkille. Käyttämällä esimerkiksi nikkelitemplaattia materiaalin synteesivaiheessa materiaalin nikkeliselektiivisyys kasvaa verrattuna perinteiseen synteesitekniikkaan. Tässä työssä tutkittiin erotusmateriaaleja, joissa oli käytetty nikkeli- tai lyijytemplaattia, vertaamalla niitä ilman templaattia syntetisoituihin materiaaleihin. Lisäksi erotustehokkuutta verrattiin kaupalliseen erotusmateriaaliin häiritsevien magnesium- ja kalsiumionien tapauksessa. Lyijyn havaittiin sitoutuvan tehokkaimmin kaikkiin syntetisoituihin materiaaleihin riippumatta nikkelitemplaatin käyttämisestä. Kinetiikkakokeet osoittivat lyijyn sitoutumisnopeudenkin olevan vertailtavista metalleista suurin. Kaikki kokeet suoritettiin huoneenlämpötilassa liuoksen pH-arvon ollessa 7,5. Nikkelitemplaatin käyttö lisäsi materiaalin selektiivisyyttä nikkelille verrattuna templaatittomaan muuten identtiseen materiaaliin. Kuitenkin materiaalien lyijyselektiivisyys oli huomattavasti nikkeliselektiivisyyttä suurempi. Lyijytemplaatin käyttö ei lisännyt lyijyselektiivisyyttä, mutta materiaalin nikkeliselektiivisyys parantui. Materiaaliin sitoutuneet nikkeli-, koboltti- ja sinkkipitoisuudet jäivät huomattavasti vähäisemmiksi verrattuna kaupalliseen materiaaliin. Magnesiumin ja kalsiumin tarttumista syntetisoituihin materiaaleihin tutkittiin myös ja tulosten mukaan IIPD2:een ja IIPD2-Methoxiin sitoutui erittäin vähän magnesiumia ja kalsiumia verrattuna kaupalliseen materiaaliin, jonka kalsiumkapasiteetti oli erityisen suuri. Kyseiset materiaalit soveltuvat tulosten perusteella myös häiritseviä ioneja sisältävien liuosten puhdistamiseen. Näin ollen valittujen kahden materiaalin jatkotutkimuksella olisi mahdollista parantaa nikkelikapasiteettia ja -selektiivisyyttä.

Pressure Drop in Vertical Core-Annular Flow

An experimental apparatus for the study of core annular flows of heavy oil and water at room temperature has been set up and tested at laboratory scale. The test section consists of a 2.75 cm ID galvanized steel pipe. Tap water and a heavy oil (17.6 Pa.s; 963 kg/m³) were used. Pressure drop in a vertical upward test section was accurately measured for oil flow rates in the range 0.297 - 1.045 l/s and water flow rates ranging from 0.063 to 0.315 l/s. The oil-water input ratio was in the range 1-14. The measured pressure drop comprises gravitational and frictional parts. The gravitational pressure drop was expressed in terms of the volumetric fraction of the core, which was determined from a correlation developed by Bannwart (1998b). The existence of an optimum water-oil input ratio for each oil flow rate was observed in the range 0.07 - 0.5. The frictional pressure drop was modeled to account for both hydrodynamic and net buoyancy effects on the core. The model was adjusted to fit our data and shows excellent agreement with data from another source (Bai, 1995).

Synthesis, characterization and chemical sensor application of conducting polymers

Polymeric materials that conduct electricity are highly interesting for fundamental studies and beneficial for modern applications in e.g. solar cells, organic field effect transistors (OFETs) as well as in chemical and bio‐sensing. Therefore, it is important to characterize this class of materials with a wide variety of methods. This work summarizes the use of electrochemistry also in combination with spectroscopic methods in synthesis and characterization of electrically conducting polymers and other π‐conjugated systems. The materials studied in this work are intended for organic electronic devices and chemical sensors. Additionally, an important part of the presented work, concerns rational approaches to the development of water‐based inks containing conducting particles. Electrochemical synthesis and electroactivity of conducting polymers can be greatly enhanced in room temperature ionic liquids (RTILs) in comparison to conventional electrolytes. Therefore, poly(para‐phyenylene) (PPP) was electrochemically synthesized in the two representative RTILs: bmimPF6 and bmiTf2N (imidazolium and pyrrolidinium‐based salts, respectively). It was found that the electrochemical synthesis of PPP was significantly enhanced in bmimPF6. Additionally, the results from doping studies of PPP films indicate improved electroactivity in bmimPF6 during oxidation (p‐doping) and in bmiTf2N in the case of reduction (n‐doping). These findings were supported by in situ infrared spectroscopy studies. Conducting poly(benzimidazobenzophenanthroline) (BBL) is a material which can provide relatively high field‐effect mobility of charge carriers in OFET devices. The main disadvantage of this n‐type semiconductor is its limited processability. Therefore in this work BBL was functionalized with poly(ethylene oxide) PEO, varying the length of side chains enabling water dispersions of the studied polymer. It was found that functionalization did not distract the electrochemical activity of the BBL backbone while the processability was improved significantly in comparison to conventional BBL. Another objective was to study highly processable poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) water‐based inks for controlled patterning scaled‐down to nearly a nanodomain with the intention to fabricate various chemical sensors. Developed PEDOT:PSS inks greatly improved printing of nanoarrays and with further modification with quaternary ammonium cations enabled fabrication of PEDOT:PSS‐based chemical sensors for lead (II) ions with enhanced adhesion and stability in aqueous environments. This opens new possibilities for development of PEDOT:PSS films that can be used in bio‐related applications. Polycyclic aromatic hydrocarbons (PAHs) are a broad group of π‐conjugated materials consisting of aromatic rings in the range from naphthalene to even hundred rings in one molecule. The research on this type of materials is intriguing, due to their interesting optical properties and resemblance of graphene. The objective was to use electrochemical synthesis to yield relatively large PAHs and fabricate electroactive films that could be used as template material in chemical sensors. Spectroscopic, electrochemical and electrical investigations evidence formation of highly stable films with fast redox response, consisting of molecules with 40 to 60 carbon atoms. Additionally, this approach in synthesis, starting from relatively small PAH molecules was successfully used in chemical sensor for lead (II).

S500 Suurlujuusteräksestä valmistettujen rakenneputkiliitosten lujuusominaisuudet

Nykyinen Eurocode 3 suunnitteluohjeen rakenneputkiliitoksia käsittelevä osio vaatii S500 suurlujuusteräksestä valmistettujen liitosten mitoituksen yhteydessä käytettäväksi reduk-tiokerrointa 0.8. Tämä on varsin konservatiivinen mitoituspa, joka vähentää merkittävästi lujemman teräslaadun käyttämisestä saavutettavaa hyötyä. Tämän työn pääasiallinen ta-voite on laboratoriotestein selvittää S500 lujuusluokan rakenneputkiliitosten todellinen äärikapasiteetti ja verrata sitä nykyisen mitoitusohjeen mukaiseen kapasiteettiin. Tässä työssä tutkitut liitokset ovat valmistettu poikkileikkaukseltaan nelikulmaisista kyl-mämuovatuista rakenneputkista. Koesarja koostui kahdeksasta X-liitoksesta, sekä kymme-nestä K-liitoksesta. Kaikki testit suoritettiin huoneenlämmössä, LUT Koneen teräsrakenne-laboratoriossa. Laboratoriotestien lisäksi rakenteen käyttäytymistä tutkittiin epälineaarisen elementtimenetelmän avulla ja näitä tuloksia verrattiin kokeellisiin tuloksiin. Sekä testien että FE–analyysin perusteella voidaan todeta, että S500 lujuusluokan terästä käytettäessä ei Eurocode 3:n mukaisen reduktiokertoimen käytölle ole perusteita.

Permuurahaishapon valmistaminen mikroreaktorissa

Kandidaatintyön teoriaosassa perehdytään mikroreaktoreihin sekä niiden etuihin ja haasteisiin. Lisäksi esitellään lyhyesti, kuinka sekoitus näissä reaktoreissa voidaan järjestää erilaisten sekoituselementtien avulla sekä uusien ainetta lisäävien valmistusmenetelmien tarjoamat mahdollisuudet reaktorien valmistukselle. Mikroreaktorien edut liittyvät pääasiassa prosessin helpompaan hallittavuuteen, mikä johtaa mm. turvallisuuden lisääntymiseen ja energiasäästöihin. Lisäksi esitellään kokeellisessa osassa lähtöaineina käytettävät vetyperoksidi ja muurahaishappo, sekä tuotteena syntyvä permuurahaishappo ja sen käyttökohteita. Permuurahaishappoa käytetään mm. desinfiointiaineiden yhtenä komponenttina. Sitä voidaan käyttää myös paperikoneen vesikierron bakteerien tappamiseen. Epästabiiliutensa vuoksi permuurahaishappo voi räjähtää jopa huoneenlämmössä, mikä aiheuttaa merkittävän riskin sen varastoinnille ja kuljetukselle. Tästä syystä työssä tutkittu menetelmä permuurahaishapon valmistamiseksi mikroreaktorissa tarjoaa hyvän vaihtoehdon permuurahaishapon tuottamiseksi suoraan tarpeeseen. Kokeellisessa osassa permuurahaishappoa valmistettiin muurahaishaposta ja vetyperoksidista käyttäen rikkihappoa katalyyttinä reaktion nopeuttamiseksi. Lämpötilan ja viipymäajan vaikutusta tutkittiin permuurahaishapon muodostumiseen. Molempien nosto vaikutti edullisesti permuurahaishapon saantoon, mutta lämpötilan nosto lisää samalla räjähdysriskiä. Mikroreaktorissa lämpötilan nosto on kuitenkin suhteessa turvallisempaa makroreaktoriin verrattuna.

Defining of the material models for stainless steels to be used in FE modeling

The aim of this work is to study the results of tensile tests for austenitic stainless steel type 304 and make accurate FE-models according to the results of the tests. Tensile tests were made at Central Research Institute of Structural Material, Prometey at Saint Petersburg and Mariyenburg in Russia. The test specimens for the tensile tests were produced at Lappeenranta University of Technology in a Laboratory of Steel Structures. In total 4 different tests were made, two with base material specimens and two with transverse butt weld specimens. Each kind of a specimen was tested at room temperature and at low temperature. By comparing the results of room and low temperature tests of similar test specimen we get to study the results of work hardening that affect the austenitic steels at below room temperature. The produced specimens are to be modeled accurately and then imported for nonlinear FEM- analyzing. Using the data gained from the tensile tests the aim is to get the models work like the specimens did during the tests. By using the analyzed results of the FE-models the aim is to calculate and get the stress-strain curves that correspond to the results acquired from the tensile tests.

Use of fiber-reinforced composite framework and thermochromic pigment in maxillofacial prostheses

The purpose of this investigation was to evaluate the possibility to enhance certain qualities of facial prostheses. Polymethyl methacrylate is still being used as base mate¬rial or clip carrier material, but it is hard and heavy, and debonding of the silicone from the acrylic base material is a frequent problem. This thesis aims to evaluate the use of fiber-reinforced composite (FRC) as framework material for maxillofacial silicone prostheses. FRC has been used as reinforcement in removable and fixed partial dentures since the 1990s. This material is lightweight and can be fabricated to compress the margins of the prosthesis slightly, to keep it tightly against the skin during jaw movements and facial expressions. Additionally, the use of a thermochromic pigment, colorless in room temperature and red in a cold environment, was studied in order to evaluate the possibility of using this color changing pigment in facial prostheses to mimic the color change of facial skin in cold weather. The tensile bond strength between pre-impregnated, unidirectional FRC and maxillofacial silicone elastomer was studied. Three different bonding agents or primers were compared. Bond strength was improved by one of the primers and by roughening the surface. The effect of a skin compressing glass fiber-reinforced composite framework on facial skin blood flow was studied by using a face mask, constructed with a compression pad corresponding to the outer margin of a glass fiber-reinforced framework beam of a facial prosthesis. The skin blood flow of ten healthy volunteers, aged 23-25 years, was measured during touch, light, and moderate compression of the skin, by using laser Doppler imaging technique. None of the compressions showed any marked effects on local skin blood flow. There were no significant differences between blood flow during compression and at baseline. Maxillofacial silicone elastomer was colored intrinsically with conventional color pigments: a control group containing only conventional pigments was compared to two test groups with 0.2 wt% and 0.6 wt% thermochromic pigment added. The color of the material was measured with a spectrophotometer in room temperature and after storage in a freezer. The color stability of the maxillofacial silicone elastomer colored with thermo¬chromic pigment was evaluated by artificial aging. The color dif¬ference of the L* (lightness) and a* values (redness), comparing color after the samples were stored at room temperature and in a freezer (-19°C), was statistically significant for both 0.2 wt% and 0.6 wt% thermo¬chromic pigment groups. The differences in the b* values (yellowness) were statistically significant for the 0.6 wt% group. Exposure to ultraviolet (UV) radiation led to visually noticeable and statistically signifi¬cant color changes (ΔE) in all color values in both test groups. The specimens containing thermochromic pigment were very sensitive to UV radiation. In conclusion, a framework of fiber-reinforced composite can successfully be bonded to maxillofacial silicone elastomer, and a framework beam, compressing the facial skin, did not remarkably alter the skin blood flow on healthy, young adults. The thermochromic pigment showed color change in maxillofacial silicone elastomer. However, artificial aging showed that it was too sensitive to UV radiation to be used, as such, in maxillofacial prostheses.

Topochemistry of physical and chemical pretreatments of biomass as investigated by FE-SEM, XPS and ToF-SIMS

Surface chemistry is of great importance in plant biomass engineering and applications. The surface chemical composition of biomass which includes lignin, carbohydrates and extractives influences its interactions with chemical agents, such as pulp processing/papermaking chemicals, or enzymes for different purposes. In this thesis, the changes in the surface chemical composition of lignocellulosic biomass after physical modification for the improvement of resulting paper properties and chemical treatment for the enhancement of enzymatic hydrolysis were investigated. Low consistency (LC) refining was used as physical treatment of bleached softwood and hardwood pulp samples, and the surface chemistry of refined samples was investigated. The refined pulp was analysed as whole pulp while the fines-free fibre samples were characterized separately. The fines produced in LCrefining contributed to an enlarged surface specific area as well as the change of surface coverage by lignin and extractives, as investigated by X-ray photoelectron spectroscopy (XPS). The surface coverage by lignin of the whole pulp decreased after refining while the surface coverage by extractives increased both for pine and eucalyptus. In the case of pine, the removal of fines resulted in reduction of the surface coverage by extractives, while the surface coverage by lignin increased on fibre sample (without fines). In the case of eucalyptus, the surface coverage by lignin of fibre samples decreased after the removal of fines. In addition, the surface distribution of carbohydrates, lignin and extractives of pine and eucalyptus samples was determined by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). LC-refining increased the amounts of pentose, hexose and extractives on the surface of pine samples. ToF-SIMS also gave clear evidence about xylan deposition and reduction of surface lignin distribution on the fibre of eucalyptus. However, the changes in the surface chemical composition during the physical treatment has led to an increase in the adsorption of fluorescent whitening agents (FWAs) on fibres due to a combination of electro-static forces, specific surface area of fibres and hydrophobic interactions. Various physicochemical pretreatments were conducted on wood and non-wood biomass for enhancing enzymatic hydrolysis of polysaccharides, and the surface chemistry of the pretreated and enzymatically hydrolysed samples was investigated by field emission scanning electron microscopy (FE-SEM), XPS and ToF-SIMS. A hydrotrope was used as a relatively novel pretreatment technology both in the case of wood and non-wood biomass. For comparison, ionic liquid and hydrothermal pretreatments were applied on softwood and hardwood as well. Thus, XPS analysis showed that the surface lignin was more efficiently removed by hydrotropic pretreatment compared to ionic liquid or hydrothermal pretreatments. SEM analysis also found that already at room temperature the ionic liquid pretreatments were more effective in swelling the fibres compared with hydrotropic pretreatment at elevated temperatures. The enzymatic hydrolysis yield of hardwood was enhanced due to the decrease in surface coverage of lignin, which was induced by hydrotropic treatment. However, hydrotropic pretreatment was not appropriate for softwood because of the predominance of guaiacyl lignin structure in this material. In addition, the reduction of surface lignin and xylan during pretreatment and subsequent increase in cellulose hydrolysis by enzyme could be observed from ToF-SIMS results. The characterisation of the non-wood biomass (e.g. sugarcane bagasse and common reed) treated by hydrotropic method, alkaline and alkaline hydrogen peroxide pretreatments were carried out by XPS and ToF-SIMS. According to the results, the action for the removal of the surface lignin of non-wood biomass by hydrotropic pretreatment was more significant compared to alkaline and alkaline hydrogen peroxide pretreatments, although a higher total amount of lignin could be removed by alkaline and alkaline hydrogen peroxide pretreatment. Furthermore, xylan could be remarkably more efficiently removed by hydrotropic method. Therefore, the glucan yield achieved from hydrotropic treated sample was higher than that from samples treated with alkaline or alkaline hydrogen peroxide. Through the use of ToF-SIMS, the distribution and localization of lignin and carbohydrates on the surface of ignocelluloses during pretreatment and enzymatic hydrolysis could be detected, and xylan degradation during enzymatic hydrolysis could also be assessed. Thus, based on the results from XPS and ToF-SIMS, the mechanism of the hydrotropic pretreatment in improving the accessibility of enzymes to fibre and further ameliorating of the enzymatic saccharification could be better elucidated.

2-(aminometyyli)pyridiini ligandin kompleksoituminen nikkelin kanssa eri liuottimissa

Kandidaatintyön tavoitteena oli tutkia 2-(aminometyyli)pyridiini ligandin kompleksoitumista nikkeli(II) ionin kanssa vesiliuoksissa ja eri orgaanisissa liuotinseoksissa. Työ tehtiin osana laajempaa tutkimusta, jossa pyritään määrittämään nikkelille spesifisiä erotusmateriaaleja ion imprinting tekniikkaa hyväksikäyttäen. Koesarjat sekä näihin liittyvä mittaukset suoritettiin kaikki huoneen lämmössä sekä normaalissa ilman paineessa. Koesarjojen liuosfaaseista määritettiin UV/Vis spektrofotometrisesti spektrit, joiden perusteella piirrettiin Job Plot kuvaajat. Kuvaajien havaittiin vastaavan aikaisemmissa tutkimuksissa määritettyjä kuvaajia sekä matemaattisesti laskettuja huippuarvoja. Saostuneiden kiintoaineiden koostumukset määritettiin XRD ja IR mittauksilla. Tuloksien perusteella todettiin 1:2 kompleksin saostuvan lähes poikkeuksetta kaikista saostuneista näytteistä. Mittaustuloksista johtopäätöksinä voidaan todeta liuotinseoksien ja veden määrän vaikuttavan muodostuneen kompleksin kiderakenteeseen, mutta ei saostuvaan kompleksiin.

Germination of spores and growth of gametophytes and sporophytes of Rumohra adiantiformis (Forst.) Ching (Dryopteridaceae) after spore cryogenic storage

Rumohra adiantiformis (Forst.) Ching is a fern (Dryopteridaceae) used in floral arrangements. Spores sterilized in 15% (v/v) solution of commercial sodium hypochlorite for 10 minutes and unsterilized spores were plunged in liquid nitrogen and held for 15 minutes and for 90 days. After the cryogenic treatments, spores were taken out of liquid nitrogen and rapidly thawed out in a water bath or slowly at room temperature and were cultured in Mohr's mineral solution as modified by Dyer, kept at 25 ± 2 ºC and a 16-hours photoperiod. Statistical differences were not observed in the germination of unsterilized spores immersed or not immersed in liquid nitrogen, but when the spores were previously sterilized, a severe inhibition of germination was observed in cryopreserved spores. Faster mean germination time was observed for unsterilized spores cryopreserved in liquid nitrogen for 15 minutes. The germination of spores stored in liquid nitrogen for 90 days reached the maximum percentage after 12 days, while control spores reached their maximum percentage after 16 days. Levels of soluble sugars did not vary among treatments in gametophytes cultivated for 10 weeks after spore inoculation. The number of fronds and the length of the longest frond on sporophytes did not differ statistically among treatments. The relative growth rate of sporophytes grown from cryopreserved and control spores were not statistically different among treatments. Spores of R. adiantiformis immersed in liquid nitrogen for 15 minutes apparently produced phenotypically normal plants.

Preparation of mitotic chromosomes of leaf-cutting ants from the genera Atta and Acromyrmex

Some modifications were made to the methodology of Imai et al. (Jpn. J. Genet. 63: 159-185, 1988) for cytogenetic analysis of the leaf-cutting ants Atta sexdens piriventris and Acromyrmex heyeri (Hymenoptera, Formicidae), shortening preparation time and improving chromosomal preparations. The brain ganglia of prepupae were dissected in a 0.0025% hypotonic solution of colchicine, placed on a glass slide on a cold plate (4 ± 1oC) for 20 min. The material was fixed directly on the cold slide (with cold fixative I), macerated with a histological needle and fixed again with fixative I, followed by fixatives II and III, all of them cold. The slide was flame-dried right after the use of fixative III, and it was allowed to air-dry at room temperature for 2 h. The resulting metaphases presented less contracted chromosomes, with separated and well defined sister chromatids at a high frequency, when the material was processed in the manner described and stained with 3% Giemsa in phosphate buffer (pH 6.8) for 15 min.

Use of a cysteine proteinase from Carica candamarcensis as a protective agent during DNA extraction

We describe the use of a plant cysteine proteinase isolated from latex of Carica candamarcensis as a protective agent during isolation of bacterial DNA following growth in culture of these cells. Between 100 to 720 units of proteinase (1 µg = 6 units) afforded good DNA protection when incubated with various kinds of microorganisms. Agarose gel electrophoresis showed that the resulting DNA was similar in size to DNA preparations obtained by treatment with proteinase K. The viability of the resulting material was checked by PCR amplification using species-specific primers. After standing at room temperature (25oC) for 35 days, the enzyme lost 10% of its initial activity. The enzyme stability and good yield of DNA suggest the use of this proteinase as an alternative to proteinase K.