Opaque Zones Research Articles

Davabirzhaot! Conflicting claims on public space in Tbilisi between transparency and opaqueness

Purpose – The purpose of this paper is to investigate the form of young male socialisation referred to as birzha, in its relation to public space in Georgia. Birzha defines a group of young men who meet regularly in urban open spaces in Tbilisi’s neighbourhoods. Partly considered as the initial step of a criminal career, belonging to birzha is a mark of identification with one’s local group. The contested nature of public space is illustrated by the conflicting relation between birzha’s bottom-up use of public space and top-down projects of urban renovation sought by Saakashvili’s government. Design/methodology/approach – Drawing upon literary and media sources, and analysing fieldwork data collected in 2008-2009 and 2014, this study explores how the announced (re)construction of public space under Saakashvili resulted in institutional interventions from above which curtailed public space’s accessibility. Findings – The present analysis points out contradictions in Saakashvili’s government’s political narrative on public space. In the institutional focus on a future of order, transparency, and democracy, birzha is an insistent reminder of an informal and corrupted past. Banned from futuristic projections of the public space, in the present birzha is annihilated by state repression, enforced in opaque zones out of public sight. Originality/value – Focusing on a largely overlooked phenomenon in social science research, the paper highlights the ways in which conflicting approaches to public space affect the relation between political institutions and citizens. Delving into ambivalent public/private divides in post-socialist societies, the study of Georgian birzha offers an original angle for investigating the contestation of urban public space in relation to political legitimacy and transparency.

Thin Fresnel zone plate lenses for focusing underwater sound

A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens.

Spatial variation in demography of an estuarine teleost: implications for population and fishery assessments

Length- and age-based information is used to assess the exploitation status of har- vested populations of fish worldwide. This study examined variability in length-at-age, length and age compositions and derived demographic parameters of Acanthopagrus australis (Sparidae) captured in beach seines in 3 estuaries across 5 yr. The method of ageing fish by counting opaque growth zones on sagittal otoliths was validated by field and aquaria studies. Length-at-age rela- tionships varied according to gender, age class and estuary. Females older than 3 yr had a signif- icantly greater mean length-at-age than males, and this was consistent across all estuaries. For both genders, mean length-at-age of fish older than 4 yr was greatest in the southernmost estuary, and least in the northernmost estuary, suggesting differential growth dynamics among estuaries. Observed longevity differed among estuaries, ranging from 14 to 22 yr. Variations in length com- position of retained catches were subtler than those for age composition. The average age of fish in catches varied among estuaries from 4.2�5.1 yr to 6.8�8.2 yr even though fish within 5 cm of the minimum legal length dominated catches in all estuaries. Estimates of total and fishing mortality varied 3-fold among estuaries, with fishing mortality exceeding natural mortality. Variability in demographic characteristics was generally greater among estuaries than among years within each estuary. These results show that the population demographics and ensuing assessments should not be extrapolated across estuaries or from one estuary to the entire A. australis population. Length is a poor predictor of age and future sampling of populations must be age-based and strat- ified to account for estuary-specific variation in demography. Failure to account for such varia - bility could confound assessments and management deliberations necessary for determining the most appropriate harvest and conservation strategies for such species.

Habitat Use Patterns ofChelon haematocheilus, as Revealed by Sr:Ca Ratios in Otoliths

ABSTRACT Hwang, S.W.; Lee, T.W.; Hwang S.D.; Lee, E.K., and Yoo, J.M. 2015. Habitat use patterns of Chelon haematocheilus, as revealed by Sr:Ca ratios in otoliths. We measured Sr:Ca ratios in otoliths to examine the habitat use patterns of 50 Chelon haematocheilus collected from two estuaries of the Geum River and the Mangyeong River on the midwest coast of South Korea. The average ratio was 5 × 10−3 ± 0.6 × 10−3 (mean ± SD) in the core of the otolith and ranged from 3 × 10−3 to 7 × 10−3 in the opaque zone surrounding the core. We applied the criteria used to analyze otoliths in the closely related species Mugil cephalus in a previous study and concluded from the otolith Sr:Ca ratios that C. haematocheilus spawns and grows in brackish water during the early part of its life cycle. Most fish showed otolith Sr:Ca ratios ranging from 3 × 10−3 to 7 × 10−3, indicating that they primarily live in brackish water. Some fish had ratios outside that range, indicating that they had potentially spent time in the uppe...

Age and growth of Sind sardine (Sardinella sindensis) using otolith from Qeshm Island (Persian Gulf)

This is the first study of growth and age of Sardinella sindensis from coastal waters of Qeshm Island (Persian Gulf) based on the sectioned otolith reading method. In total, 128 fishes were collected randomly from purse seine commercial nets during March 2011 to February 2012. The annual formation of the growth rings were determined by counting the opaque and translucent zones occurrence at the outer margin of the otolith. The peak of opaque and translucent zones formation occurred in June and January, respectively. There was no significant differences between the sex ratio of males to females (p>0.05). The total length and body weight for both sexes ranged between (7.918.6 cm) and (3.98-55.69 g). In total, four age classes were determined, and the maximum age was recorded as 3.5 years. The most abundant individuals were counted in 1 + age class, while the least number of fishes belonged to the 3 + age class. The nonlinear regression relationship between the length and age for combined sexes were fitted in Von Bertalanffy growth equation, and described as: TL= 20.8 (1-e -0.54(t+ 0.54) ). There was a strong relationship between the body weight and total length of the fishes (p>0.05), indicating that the growth type of S. sindensis is isometric. From the results of this study we concluded that S. sindensis is a fast-growing species with a short-life span. In order to obtain more reliable results about the age and growth of this species, we suggest that different methods of age determination should be used, combined with the evaluation of the factors affecting its growth for the management of optimum exploitation of the resources of this fish.

Age and Growth of the Areolate Grouper <i>Epinephelus areolatus</i> from the Gulf of Suez

Age and growth of the associated coral reef grouper, Epinephelus areolatus, were estimated for samples collected from the artisanal fishery in the Gulf of Suez during November 2013 and October 2014. Otoliths of 597 specimens ranged in length from 11.2 to 50.5 cm were used in age determination. The otoliths showed alternating opaque (light) and translucent zones when seen by reflected light against a dark background, a translu¬cent zone plus the opaque zone immediately around it formed an annulus. According to the otolith examination, the maximum life span of E areolatus was eight years with mean lengths of 16.9, 24, 29.9, 35.7, 39.7, 43.4, 46.6 and 49.7 cm for the age groups from one to eight respectively. Individuals belong to age group two constituted the bulk of the catch with more than 60% of the population. The results showed that the E. areolatus is a relatively slow growing species and the values of the von Bertalanffy growth function was estimated as K = 0.154, L∞ = 66.55 cm (LT) and t0 = −0.91 years. The estimated growth performance index is 2.83. The length weight relationship was estimated as a = 0.0135 and b = 2.9947, r2 =0.981 indicating an isometric growth of the weight relative to the length.

Studies of the age and growth of alfonsino Beryx splendens (Berycidae) in the area of the Azores Banks compared to other areas of its habitation

Methods of determining age of alfonsino Beryx splendens in the area of the Azores Banks are described. On otoliths of the beryx, spawning marks form in the period of intensive spawning (June–September); those of hyaline zone form in the season of lowest water temperature in the considered area (January–March); and those of opaque zone form in the prespawning (April–May) and postspawning (October–December) periods. The growth of alfonsino in the northern part of the Atlantic is close to an isometric one. The rate of linear growth of alfonsino in the area of the Azores Banks in the first year of life is higher than in fish of the New Anyo Seamount and Vavilov Ridge but lower than at the Angular Seamount. Beginning from the second year of life, the rate of growth slows down and becomes lower than at the New Anyo and Angular seamounts, but it remains higher than the rate of growth of fish of the Vavilov Ridge.

Lecithinase-producing bacteria in commercial and home-made foods: Evaluation of toxic properties and identification of potent producers

The aim of this study was to determine bacterial contamination in 28 refrigerated and unrefrigerated, commercial and home-made food items in Al Madinah Al Munawarah, Saudi Arabia. Of the 60 bacterial strains isolated, 53 were recovered from food samples refrigerated for 7 days and 7 from fresh, unrefrigerated food. The isolated bacteria were screened for lecithinase enzyme (toxin) production by the cup plate clearing zone technique. All isolates were positive on the basis of their ability to grow aerobically on egg yolk agar, giving black colonies as a characteristic feature of lecithinase production and opaque zones with diameters of 4–27mm. Isolates were categorized into low, moderate and high lecithinase producers. Potent lecithinase-producing strains isolated from refrigerated green pepper (PS1) and lettuce (LS1) had a remarkably large zone measuring 27±1.9mm. All isolates also had additional toxic properties, including caseinase and haemolytic activities. Genotypic characterization by amplified ribosomal DNA restriction analysis showed that strains PS1 and LS1 were from same genus. Phenotypic characterization with biochemical tests and the Phoenix identification system suggested their affiliation to the Bacillus group. 16S rDNA sequence analysis of both strains showed them to be Bacillus cereus, with 99% sequence similarity to B. cereus strain J8B-67.

Age and Growth of the Ark ShellScapharca broughtonii(Bivalvia, Arcidae) in Japanese Waters

ABSTRACT Age and growth of the ark shell Scapharca broughtonii in 3 bays in Japan (Mutsu, where ark shells are cultured, and Nanao and Sendai, where they occur naturally) were examined using a shell sectioning and staining method. When a water-based marking pen was used to stain the opaque zones only in shell cross-sections, unstained translucent zones (i.e., growth rings) were clearly observed. Based on seasonal changes in marginal structures of shell cross-sections and marginal growth indices (MGIs), growth rings were estimated to be formed annually in summer when shell growth ceased. The estimated maximum ages for ark shells from Nanao and Sendai bays were 6 y and 20 y, respectively, whereas for Mutsu Bay the maximum age was not calculated because we had only young, cultured specimens, von Bertalanffy growth models were estimated as Lt = 80.1(1 -e -0.365(t+ 0-160) for Mutsu Bay, Lt = 115.3(1-e -0.478t-0162) for Nanao Bay, and Lt = 84.8(1 -e -0.473(t + 0.222) for Sendai Bay. There was no significant dif...

Age, Growth, and Mortality of Yellowmouth Grouper from the Southeastern United States

AbstractThe Yellowmouth Grouper Mycteroperca interstitialis is a member of the snapper–grouper complex that is managed by the South Atlantic Fishery Management Council. There is little published life history information—specifically age–growth parameters—for use in assessing the resource. We sampled Yellowmouth Grouper from the fisheries along the southeastern U.S. coast from 1980 to 2012 (n = 391), determining ages by counting opaque zones on sectioned sagittal otoliths. Opaque zones were annular, forming in May–August with a peak in May and June. Yellowmouth Grouper age ranged from 3 to 31 years, and the largest fish was 859 mm FL. Body size relationships were as follows: whole weight W (g) = (8.89×10−6)(FL, mm)3.07 (n = 339; r2 = 0.96); W (g) = (1.13×10−5)(TL, mm)3.01 (n = 165; r2 = 0.96); and TL (mm) = 10.09 + [1.05×(FL, mm)] (n = 162; r2 = 0.98). The von Bertalanffy growth equation for Yellowmouth Grouper was Lt (length at age t) = 755[1 − e−0.14(t + 1.42)] when the model included an adjustment for minimum size limits and was Lt = 772[1 − e−0.11(t + 4.18)] when the model was not adjusted. Natural mortality (M) estimated by Hewitt and Hoenig's (2005) longevity‐based method was 0.14. Age‐specific estimates of M were obtained with the Charnov et al. (2013) method. The selection of growth model (size limit adjusted versus unadjusted) had a marked effect on M for the earliest ages: M was 1.22 versus 0.43 for age 0; 0.72 versus 0.35 for age 1; 0.51 versus 0.29 for age 2; 0.40 versus 0.26 for age 3; 0.33 versus 0.23 for age 4; and 0.29 versus 0.21 for age 5. We believe that these life history parameter estimates are accurate for Yellowmouth Grouper in southeastern U.S. fisheries.Received June 6, 2013; accepted November 12, 2013

Age and maturation of jack mackerel Trachurus japonicus in the East China Sea

Growth and reproductive characteristics of jack mackerel Trachurus japonicus collected in the East China Sea were determined based on otolith readings and gonad histology, respectively. Translucent and opaque zones on sectioned otoliths were identified and opaque rings counted. Von Bertalanffy growth parameters did not significantly differ between males and females, and the combined growth curve was: Lt = 401{1 − exp[−0.275 (t + 1.149)]} (0.8 < t < 6.9), where Lt is fork length (mm) at age t. The calculated lengths at age 1 in our study were larger than those reported 50 years ago from the East China Sea. The spawning period was evaluated to be from December to June, but primarily from February to May, based on the monthly changes in the gonadosomatic index and histological observations. The minimum size and age at first maturity were smaller and younger, respectively, than those reported in previous studies.

Age and growth of three rockfish species, Sebastes inermis, S. ventricosus and S. cheni, in the central Seto Inland Sea, Japan

Inter-specific comparison of growth was conducted among three Sebastes species (Sebastes inermis, Sebastes ventricosus and Sebastes cheni) which have previously been treated as a single species before the 2008 taxonomic review. Fish were collected in April 2010 for DNA analysis and each month from June 2011 to May 2012 for growth analysis in the central Seto Inland Sea, southwestern Japan. AFLP analysis of each of the three Sebastes species confirmed significant frequency differences in fragments. The result supported the identification of the three Sebastes species based on the morphological characters. Analysis of otoliths from a total of 94 S. inermis, 125 S. ventricosus and 71 S. cheni showed that an opaque zone at the outer margin of the sagittal otolith increased from April to October and the zone was validated as an annual ring. Growth of the three Sebastes species was estimated using the von Bertalanffy growth formula. There was no significant difference in the growth formulas between males and females within each species. The growth patterns among the three Sebastes species were significantly different and S. inermis grows slower than S. ventricosus and S. cheni in the central Seto Inland Sea.

Age and Growth Study of the Jack Mackerel (Trachurus japonicus) in the Northeatern Waters off Taiwan

Jack mackerel (Trachurus japonicus) is one of the most important fish resources in the northeastern Taiwan. Because of the flourishing of Taiwanese seiner fisheries in recent years, the proportion and catch of jack mackerels have increased. However, the studies on their age and growth are outdated, thus data on the catch-at-age composition are lacking. The present study collected jack mackerel otolith samples from May, 2010, to April, 2011, for age determination and combined those data with length and weight data from 2005 to January, 2012, to investigate the catch-at-age of jack mackerel in the northeastern waters off Taiwan. The regression equations for fork length (FL) and body weight (BW) of jack mackerel were significantly different between females and males (p ＜ 0.05). The equations were BW = 3.6 × 10^(-2) × FL^(2.6771) for females and BW = 3.2 × 10^(-2) × FL^(2.7108) for males. The formation of opaque zones was used as the standard for ring calculation. Ring formation occurred once every year during January and February regardless of sex. The obtained ages and corresponding FL data were introduced into the von Bertalanffy growth function showing that the maximum FL was 40.4 cm with growth coefficient of 0.223 yr^(-1). The jack mackerel catch in the northeastern waters off Taiwan were the age-0 (39%) and age-1 (38%), with high proportion of immature fish.

Sclerochronological studies reveal that patterns of otolith growth of adults of two co-occurring species of Platycephalidae are synchronised by water temperature variations

Chronologies are developed from the otolith growth-increment widths of adult rock flathead (Platycephalus laevigatus) and longhead flathead (Leviprora inops) collected from three inter-connected embayments in temperate south-western Australia. Marginal increment trends on otoliths, in combination with the dendrochronological technique of crossdating, provide strong evidence that an opaque zone is formed annually in the otoliths of both species. Increment widths between opaque zones in the otoliths of individuals of P. laevigatus (maximum age 20 years) and L. inops (maximum age 21 years) were synchronised within and between species. The correlation between the two master otolith chronologies, i.e. mean standardised increment width for each year, was highly significant (P < 0.01). The master otolith chronology for each species was positively correlated with mean sea surface temperatures from 1 July to 30 June, which encompassed the austral summer when growth is typically greatest, and with mean monthly sea surface temperature between September and March. Leeuwin Current strength, which influences the biotic characteristics of some marine species on the south coast, has little influence on the pattern of otolith growth, presumably because the inter-connected embayments from which fish were obtained were partially enclosed. On the basis of the above data and the geographical distributions of P. laevigatus and L. inops, it is proposed that, while both species would grow faster with increasing temperature, the temperatures on the south coast are closer to the optimum for the former species.

First attempt to age yellowfin tuna, Thunnus albacares, in the Indian Ocean, based on sectioned otoliths

This study first attempts to investigate the age and growth of yellowfin tuna in the Indian Ocean and clarifies its sex-specific growth using sectioned otoliths. The results indicate that the assumption of annual opaque zones may be reliable and fish age at the first opaque zone formation is about 0.75 years. The age estimates cover a large range of lifespans (age estimates range from 0.75 to 10.50 years) in which the maximum age estimate shows that males (9.50 years) are older than females (6.50 years). The estimated von Bertalanffy growth curves are shown to be significantly different between sexes, while the von Bertalanffy growth parameters (L∞, k and t0) are 123.6cm, 0.846 year−1 and −0.449 years for females and 162.9cm, 0.244 year−1 and −2.139 years for males. The growth curves of both sexes are similar before 4 years, after which males start to grow larger than females. Sexual size dimorphism in growth curves occurs after mature age.

한국 서해 대구, Gadus macrocephalus (Tilesius)의 성장특성

The age and growth of the Pacific cod, Gadus macrocephalus were investigated using left sagittal otoliths of 682 individuals collected in the West Sea of Korea from January to December 2007. The seasonal changes in the ratio of an opaque zone to interval between annular rings revealed that the narrow translucent parts of the otolith were annual growth rings formed between February and March once a year. The spawning period was December to January and therefore the duration from fertilization to the complete formation of the opaque zone became thirteen months. From the parameters calculated using the average length when the year ring was formed, the estimated von Bertalanffy growth equations were $L_t

Polyacrylamide phantom for self-actuating needle–tissue interaction studies

This study presents a polyacrylamide gel as a phantom material for needle insertion studies specifically developed for self-actuating needles to enhance the precise placement of needles in prostate. Bending of these self-actuating needles within tissue is achieved by Nitinol actuators attached to the needle body; however these actuators usually involve heating that can thermally damage the tissue surrounding the needles. Therefore, to develop and access feasibility of these needles, a polyacrylamide gel has been developed that mimics the thermal damage and mechanical properties of prostate tissue. Mechanical properties of the polyacrylamide gel was controlled by varying the concentrations of acrylamide monomer and N,N-methylene-bisacrylamide (BIS) cross-linker, and thermal sensitivity was achieved by adding bovine serum albumin (BSA) protein. Two polyacrylamide gels with different concentrations were developed to mimic the elastic modulus of the tissue. The two phantoms showed different rupture toughness and different deflection of bevel-tip needle. To study the thermal damage, a Nitinol wire was embedded in the phantom and resistively heated. The measured opaque zone (0.40mm) formed around the wire was close to the estimated damage zone (0.43mm) determined using the cumulative equivalent minutes at 43°C.

Age estimation and validation for South Pacific albacore Thunnus alalunga

Validated estimates of age are presented for albacore Thunnus alalunga, sampled from a large part of the south-western Pacific Ocean, based on counts of annual opaque growth zones from transverse sections of otoliths. Counts of daily increments were used to estimate the location of the first opaque growth zone, which was completed before the first assumed birthday. The periodicity of opaque zones was estimated by marginal increment analysis and an oxytetracycline mark-recapture experiment. Both validation methods indicated that opaque zones formed over the austral summer and were completed by autumn to winter (April to August). The direct comparison of age estimates obtained from otoliths and dorsal-fin spines of the same fish indicated bias, which was assumed to be due to poor increment clarity and resorption of early growth zones in spines, resulting in imprecise age estimates. As such, age estimates from otoliths are considered to be more accurate than those from spines for T. alalunga. This is consistent with results for a growing number of tropical and temperate tuna Thunnini species. It is recommend that validated counts of annual growth zones from sectioned otoliths is used as the preferred method for estimating age-based parameters for assessment and management advice for these important stocks.

How do the organic and mineral fractions drive the opacity of fish otoliths? Insights using Raman microspectrometry

We investigated the relationships between the opacity and the physico-chemical characteristics of fish otoliths and more specifically their aragonite and organic fractions. The analysis of these two fractions on otolith macrostructures was performed using Raman microspectrometry on both translucent and opaque zones of otoliths of pollock (Pollachius virens) and European hake (Merluccius merluccius). The magnitude of the Raman signatures of the aragonite and organic fractions were strongly correlated to otolith opacity with maxima in translucent zones. Opacity models, built from Raman signatures, successfully predicted the observed opacity for both species. A partial decorrelation of different aragonite signatures between translucent and opaque zones was revealed and discussed in terms of organisation (size, orientation) of aragonite crystals. Two categories of organic signatures with opposite effects on the opacity were identified, suggesting differences in organic compounds and (or) variations in their relative quantities. These original contributions provided new insight for understanding otolith biomineralization mechanisms as well as for interpreting and discriminating otolith macrostructures.

Exceptional longevity, slow growth and late maturation infer high inherent vulnerability to exploitation for bass groper Polyprion americanus (Teleostei: Polyprionidae)

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 18:161-174 (2013) - DOI: https://doi.org/10.3354/ab00501 Exceptional longevity, slow growth and late maturation infer high inherent vulnerability to exploitation for bass groper Polyprion americanus (Teleostei: Polyprionidae) Corey B. Wakefield*, Stephen J. Newman, Dion K. Boddington Western Australian Fisheries and Marine Research Laboratories, Department of Fisheries, Government of Western Australia, PO Box 20, North Beach, Western Australia 6920, Australia *Email: corey.wakefield@fish.wa.gov.au ABSTRACT: The bass groper Polyprion americanus is a large demersal teleost (>1.5 m) that inhabits deep continental and oceanic island slopes (50 to 1000 m). Currently, this species is considered Critically Endangered by the IUCN and there is a moratorium on its capture in Brazil. Fishing for this species is no longer commercially viable in Bermuda and they are fully protected in South Africa. In most other locations, this species is rarely encountered and knowledge of its biology and catch history is limited. In the present study, specimens were collected from recreational and commercial catches (n = 151) in the southeastern Indian Ocean from 2005 to 2012. Otolith edge analysis was used to verify that a single opaque zone was deposited annually from May to September. A maximum age of 78 yr for females and 55 yr for males was determined from thin transverse sections of otoliths. The spawning period of this gonochorist was from autumn to early winter (March to June) and partitioned prior to that of the sympatric congener P. oxygeneios (June to September). The lengths and ages at which 50% of females and males matured were 944 and 808 mm total length, and 14.4 and 11.2 yr, respectively. The exceptional longevity, slow growth and late maturation of P. americanus imply a high inherent vulnerability at relatively low levels of exploitation. As such, the overexploitation of P. americanus in both Brazil and Bermuda should warrant close scrutiny in the waters off southwestern Australia, where exploitation of deepwater fisheries resources has increased. KEY WORDS: Life history · Age · Thin otolith sections · Natural mortality · Spawning period · Deepwater · Reproduction · Continental slope · Indian Ocean Full text in pdf format PreviousNextCite this article as: Wakefield CB, Newman SJ, Boddington DK (2013) Exceptional longevity, slow growth and late maturation infer high inherent vulnerability to exploitation for bass groper Polyprion americanus (Teleostei: Polyprionidae). Aquat Biol 18:161-174. https://doi.org/10.3354/ab00501 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 18, No. 2. Online publication date: April 30, 2013 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2013 Inter-Research.