Contamination-free Environment Research Articles

Does human movement-induced airflow elevate infection risk in burn patient’s isolation ward? A validated dynamics numerical simulation approach

An isolation ward requires a highly controlled and contamination-free environment since the settling of bacteria-carrying particles (shed by medical staff) on patients’ wounds could cause infections. The present study examines the effect of medical staff’s walking movement on airflow distribution and particle dispersion. Three different walking speeds of 0.25 m/s, 0.5 m/s, and 1.0 m/s were assigned to the medical staff. An RNG k-ɛ model based on the Reynolds-Averaged Navier-Stokes (RANS) equation was adopted to predict the airflow, while a Lagrangian tracking approach was selected to track particle dispersion. The reliability of the selected airflow turbulent model and particle tracking approach was validated using published data. The present study showed that the low-pressure region behind the moving medical staff’s body has induced wake. The higher walking speed of 1.00 m/s produced a significant secondary airflow of 1.12 m/s, while 0.25 m/s and 0.5 m/s generated lower secondary airflow of 0.41 m/s and 0.53 m/s, respectively. The number of particles settled on the patient at 0.25 m/s, 0.50 m/s, and 1.00 m/s were 31, 18 and 5, respectively. Present finding indicated that a higher walking speed reduces the number of particles settled on the burn patient, therefore potentially reducing the associated nosocomial infection risk.

Exploitation of distillation region diagrams for energy-efficient and cost-effective treatment of a hazardous effluent discharged from semi-conductor industries

The hazardous nature of certain azeotropic mixtures has urged the researchers to explore the separation techniques which can impart a contamination free environment. Despite of causing environmental concerns, these azeotropic mixtures are responsible for causing serious health issues to humans and animals. More specifically, in this article, we have taken Tetrahydrofuran (THF) - water azeotropic mixture into consideration. It has been reported that it affects the central nervous system, liver, as well as can cause carcinogenicity. To be more precise, in this article, two different entrainers has been evaluated on their merits of exploiting liquid-liquid phase envelope for separating Tetrahydrofuran-water binary azeotropic mixture. The process flow sheet schematic with n-octane as entrainer (having two distillation regions) has a reduced operating energy requirement by 21.11% while comparing with the Residue Curve Map of n-hexane as entrainer having three distillation regions. The total capital cost for THF-water-n-octane case has been found to be 7.1 $/y × 105 and that of THF-water-n-hexane case has been found to be 9 $/y × 105. However, in both of the cases, the product purity of 99.9% has been achieved for THF. Also, the classical trade-off between capital cost and energy cost has been shown in this study. The salient feature of this work is the use of dynamic simulation to understand the effect of recycle flow rate induced process operational in-feasibility due to distillation region shift.

Comparative analysis of the in-vitro effects of various sterilization techniques and different disinfectants on the micropropagation of explants of Asparagus Racemosus

Asparagus racemosus belongs to the Asparagaceae family and the Asparagus genus is an endangered plant species that have been listed in the red data book. For the conventional breeding of the Asparagus racemosus, its tubers are used whichpossess a wide range of antioxidants, leading to the wastage of highly oxidative tuber roots. Using the in-vitro propagation method we can propagate Asparagus racemosus using its nodal explants successfully only in a contamination-free environment. The sources of contamination can be present in the media or associated with the explantswhich need to be eradicated using various sterilization techniques and disinfectants. This paper presents two different sterilization techniques and treatment of disinfectant Sodium hypochlorite used to sterilize the media and the explants. The media was sterilized using an autoclave and microwave oven with the treatment of explant with sterilizing agent sodium hypochlorite in three concentrations of 5%, 10%, and 15% for 5 min. The nodal explants were cultured in MS basal medium supplemented with 30g sucrose, as a carbon source and 7g agar, as a gelling agent. The temperatureinside the growth chamber was maintained at 24±2°C with a photoperiod of 16 h daylight and 8 h dark.

New Paradigms for Familiar Diseases: Lessons Learned on Circulatory Bacterial Signatures in Cardiometabolic Diseases.

Despite the strongly accumulating evidence for microbial signatures in metabolic tissues, including the blood, suggesting a novel paradigm for metabolic disease development, the notion of a core blood bacterial signature in health and disease remains a contentious concept. Recent studies clearly demonstrate that under a strict contamination-free environment, methods such as 16 S rRNA gene sequencing, fluorescence in-situ hybridization, transmission electron microscopy, and several more, allied with advanced bioinformatics tools, allow unambiguous detection and quantification of bacteria and bacterial DNA in human tissues. Bacterial load and compositional changes in the blood have been reported for numerous disease states, suggesting that bacteria and their components may partially induce systemic inflammation in cardiometabolic disease. This concept has been so far primarily based on measurements of surrogate parameters. It is now highly desirable to translate the current knowledge into diagnostic, prognostic, and therapeutic approaches.This review addresses the potential clinical relevance of a blood bacterial signature pertinent to cardiometabolic diseases and outcomes and new avenues for translational approaches. It discusses pitfalls related to research in low bacterial biomass while proposing mitigation strategies for future research and application approaches.

Mobile Microrobots for In Vitro Biomedical Applications: A Survey

The demand in the biomedical field for fast and precise devices for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> applications has increased in recent years. Mobile microrobots are significantly suitable for such applications and are developing rapidly. These microrobots offer untethered actuation toward a contamination-free environment while allowing for fast and precise handling of biological entities for applications such as positioning, sensing, delivery, and cell surgery that are highly effective for new drug discoveries and improving our understanding of cells’ behavior on the single-cell level. Here, we present a review of the recent state of the art in the actuation and implementation of mobile microrobots for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> applications. We first explore the widely used methods of wireless actuation. Next, we address the challenge of implementing an on-board interaction technique to handle the target biological entity without affecting the actuation of the microrobot. Finally, we discuss the future directions that would draw the basic outline for the next generation of mobile microrobots for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> applications.

P–758 The efficacy, safety and proven security of microSecure vitrification offers “peace of mind” and reliability during a global pandemic

Study questionUnder deadly pandemic conditions involving the novel SARS-CoV–2 corona virus, could biopsied blastocysts be safely cryopreserved, stored and utilized for subsequent warming cycles?Summary answerBlastocysts were securely stored, effectively warmed and safely transferred to yield normal pregnancy outcomes under uncertain laboratory conditions subject to unprecedented policy changes.What is known alreadyBy April 2020, every IVF lab worldwide was implementing deep cleaning/disinfecting procedures in their laboratory and patient-contact areas, thorough hand-washing policies and mandatory PPE to reduce the chance of contact transmission and spread of the potentially deadly SARS-CoV–2 coronavirus. Furthermore, we know that safeguards like oil overlay culture dishes and pipetting dilution factors provide insurance against possible contamination. However, knowing that the trophectoderm of blastocysts possessed the ACE–2 binding receptor, potential concern existed regarding the continuation of laser zona opening and biopsy procedures that could possibly expose cryopreserved embryos to the coronavirus in liquid nitrogen storage (vapor or liquid).Study design, size, durationBetween March 8 and December 22, 2020, 508 patients performed FET cycles involving the use of single (n = 490) or dual (n = 18) euploid microSecure vitrified blastocysts. In this retrospective analysis, we compared clinical pregnancy outcomes to a 5 year dataset (2015–2019) encompassing 2768 single and 272 dual embryo transfer FET cycles. All blastocysts were vitrified using a closed microSecure system and Innovative Cryoenterprise (ICE; NJ, USA) non-DMSO, glycerol-EG solutions. Differences were assessed by Chi-square analysis (p < 0.05).Participants/materials, setting, methodsDeep cleaning was performed with Simple Green Pro3+ Virucide in non-lab areas (e.g., ET rooms, waiting room) and 6% H2O2 & OoSafe solutions to disinfect lab surfaces and equipment. Group embryo cultures were performed in MCO–5M humidified incubators under low oxygen tri-gas conditions with varying CO2 levels (5.3–6.0%; pH = 7.3–7.35) using 25µl droplets of LifeGlobal medium+7.5%LGPS+1%sodium hyaluronate, before changing to 10µl droplet/GPS dishes post-biopsy. FET cycles involved 4-step sucrose dilutions and transvaginal ultrasound-guided embryo transfers.Main results and the role of chanceWhile ICSI fertilization rates were unchanged in 2020 (79.4% 2PN vs 77.3%), blastocyst utilization rates tended to be slightly lower than past years (56.4% vs 59.9%) but within an acceptable range. Of 529 blastocysts warmed, 527 (99.7%) survived completely for transfer, being comparable to the 99.4% experienced over 5 years. Furthermore, there was no differences detected in single embryo transfer pregnancy outcomes. The implantation and ongoing clinical pregnancy/live birth rates were 69% and 66.53% compared to 70.4% and 65.1%, respectively. Under pandemic conditions we did not observe an increase in biochemical pregnancies (10.3%) nor spontaneous miscarriage rates (7.8%). Although it is possible that our rigorous disinfection practices could have attributed to lower blastocyst production, the viability of those embryos was not compromised. Importantly, we were able to feel comfortable performing micromanipulation and cryopreservation procedures throughout the year knowing that we were effectively eliminating possible vertical transmission of coronavirus to an exposed trophectoderm layer in cryostorage by applying mircoSecure vitrification. Post-FET clinical check-ups revealed no patient reporting any fever or other Covid–19 symptoms in the weeks following their transfers. We are fortunate to say that our Lab staff, physicians and patients have remained healthy throughout 2020.Limitations, reasons for cautionBlastocyst survival and viability are independent of possible viral exposure. Previously, the risk of disease transmission via liquid nitrogen or vapor exposure was considered highly unlikely (Pomeroy et al., 2010), but that was at a time when embryos were primarily zona-enclosed. Today’s ART standards have us re-evaluating safer approaches.Wider implications of the findings: We have effectively mitigated avoiding performing zona opening procedures by employing our standard practice of aseptic, closed vitrification. In combination with standard preventative measures (PPE, hand hygiene, distance awareness) and routine deep cleaning practices, we sustained a contamination-free environment and healthy patients, capable of sustaining high levels of pregnancy success.Trial registration numberNot applicable

A Passive Microfluidic Device for Chemotaxis Studies.

This work presents a disposable passive microfluidic system, allowing chemotaxis studies, through the generation of a concentration gradient. The device can handle liquid flows without an external supply of pressure or electric gradients, but simply using gravity force. It is able to ensure flow rates of 10 µL/h decreasing linearly with 2.5% in 24 h. The device is made of poly(methylmethacrylate) (PMMA), a biocompatible material, and it is fabricated by micro-milling and solvent assisted bonding. It is assembled into a mini incubator, designed properly for cell biology studies in passive microfluidic devices, which provides control of temperature and humidity levels, a contamination-free environment for cells with air and 5% of CO2. Furthermore, the mini incubator can be mounted on standard inverted optical microscopes. By using our microfluidic device integrated into the mini incubator, we are able to evaluate and follow in real-time the migration of any cell line to a chemotactic agent. The device is validated by showing cell migration at a rate of 0.36 µm/min, comparable with the rates present in scientific literature.

Heat Sources in a Biosafety Cabinet Compromise Experimental and User Protection

Introduction: Keeping a contamination free environment in the laboratory has commonly been achieved by one of two ways: a flame or a biosafety cabinet (BSC). However, it has been frequently observed that these two practices have been combined, where a heat source has been used within the BSC. As flames require flammable gasses and cause hot air to rise, it was hypothesized that these could lead to a loss of BSC containment, as BSCs rely on unidirectional downflow air. Objectives: The objective of this study was to determine whether BSCs can maintain containment when a heat source is operated within the work area. Methods: Several heat sources (Bunsen burner, High Heat Bunsen Burner, Spirit Lamp and Bacti-cinerator) were placed within two sizes of BSCs (4-foot and 6-foot), and smoke was used to visualize airflow disturbances, air cleanliness was measured by particle counting , and aerosol microbiological testing was conducted to ascertain containment. The risk of introducing a flammable gas into a BSC was also calculated. Results: Large flamed Bunsen burners were found to have the most detrimental effects on the ability of the BSC to maintain containment, especially in the center of the work area, while the smaller heat sources were more variable. Containment was completely lost in the 4-foot BSC, whereas the 6-foot BSC was capable of maintaining containment in only a few conditions. The BSC was also calculated to be able to maintain the required volume of flammable gas needed to operate the burners, not taking into consideration unintended leaks. Conclusions: Overall, it was determined that BSCs cannot operate safely and reliably while housing a heat source, as it could cause unexpected contamination of the work or the worker, or BSC ignition or explosion.

Alginate Encapsulation of Trichoderma harzianum as Biocontrol Agent against Brown spot Disease on Rice (Oryza sativa) in Vitro Assays

Brown spot caused by Bipolaris oryzae is an important rice disease which can cause a reduction in yield and grain quality in Malaysia. The application of chemical agents in controlling the brown spot disease can cause undesirable effects such as residual toxicity, environmental pollution, and development of pathogen resistance to fungicides. Instead, biocontrol methods have to be developed to ensure environmental safety, the longevity of usage while effective methods of plant disease management. However, to the best of our knowledge, no research has been conducted about alginate encapsulation of Trichoderma harzianum. Therefore, the objectives for this study is to measure the performance of encapsulation of Trichoderma harzianum isolates in controlling the brown spot disease on rice. Alginate encapsulation was produced from conidial suspension by adding sodium alginate and calcium chloride which result in small beads. The isolate was isolated and characterized based on morphological characters and have been proved by pathogenicity tests. Based on the results dual culture test showed the highest percentage inhibition of radial growth which was 85.07% with 10 replication of Bipolaris oryzae. The findings from this study can be used as an alternative method to control brown spot disease which will render easier application to rice plantation in the future which suit for commercial purposes and contamination-free environment.

Rapid Quantitative Fluorescence Detection of Copper Ions with Disposable Microcapsule Arrays Utilizing Functional Nucleic Acid Strategy

In this work, an economical and easy-to-use microcapsule array fabricated by ice printing technique has been realized for ultrasensitive fluorescence quantification of copper ions employing functional nucleic acid strategy. With ice printing, the detection reagents are sealed by polystyrene (PS) film isolation and photopolymer, which guarantees a stable and contamination-free environment for functional nucleic acid reaction. Our microcapsule arrays have shown long-term stability (20 days) under −20 °C storage in frozen form before use. During the Cu2+ on-site detection, 1 μL sample is simply injected into the thawy microcapsule by a microliter syringe under room temperature, and after 20 minutes the fluorescence result can be obtained by an LED transilluminator. This method can realize the detection limit to 100 nM (100 fmol/μL) with high specificity.

Revisiting the Life-Cycle of Pasteuria penetrans Infecting Meloidogyne incognita under Soil-Less Medium, and Effect of Streptomycin Sulfate on its Development.

Pasteuria penetrans is a Gram-positive, endospore forming soil bacterium, infecting root-knot nematodes, Meloidogyne spp. Being obligate in nature, the bacterium is not easily grown in vitro, and the in vivo culturing technique is relied on the soil-based microcosm since long. Hence, culturing of P. penetrans using CYG germination pouches as a soil-less medium for plant growth, promises to provide a contamination free environment along with ease in isolation of infected females from the plant roots. Additionally, this method increases the percentage of P. penetrans infected nematode females as compared with the soil-based system. Schematic observation of all the life stages of P. penetrans was documented, which revealed chronological fragmentation of vegetative microcolony inside the nematode body demonstrating the formation of some stages not reported earlier. Further, germination of endospores attached to infective juveniles was found to be most likely asynchronous as single female nematode contained most of the developing stages of P. penetrans concurrently. Additionally, the effect of an antibiotic, streptomycin sulfate was evaluated for effects on the growth and development of the bacterium at different concentrations. Higher doses of antibiotic were found to exert a negative impact on the development of P. penetrans , which shows the incompatibility of Pasteuria and streptomycin sulfate.

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Disruption of the stress response in wastewater treatment works effluent-exposed three-spined sticklebacks persists after translocation to an unpolluted environment.

The hypothalamic-pituitary-adrenal/interrenal (HPA/I) axis plays a key role in responding to biotic and abiotic challenges in all vertebrates. Recent studies have shown that the apical response of the HPI axis to stressors in three-spined sticklebacks varies in proportion to the concentration of wastewater treatment works (WWTW) effluent to which the fish are exposed. This study was conducted to determine whether between-site variation in stress responsiveness among WWTW effluent-exposed sticklebacks is persistent or reversible. Sticklebacks from eight sites in north-west England affected by WWTW effluent and exhibiting between-population variation in HPI axis reactivity, were moved to a clean-water aquarium environment. After five months in the contaminant-free environment the responsiveness of these fish to a standardised stressor was determined, by measuring the rate of stress-induced cortisol release across the gills, and compared with the responses of fish newly sampled from the eight original capture sites. Inter-site differences in the reactivity of the HPI axis, proportional to the effluent concentration at each site, persisted among the translocated female sticklebacks for at least 5 months. In male fish however, the direct relationship between stress responsiveness and site-specific effluent was not evident 5 months post-translocation. These results support previous observations that the HPA/I axis, a non-reproductive endocrine system, is vulnerable to modulation by anthropogenic factors in fish and show for the first time that, in female fish at least, this modulation is not transient. The mechanisms underlying these observations, and the implications for the fitness and resilience of affected populations, requires investigation.

Ruch turystyczny na obszarze Puszczy Białowieskiej w świetle badań

The increasing popularity of tourist trips as a form of leisure activity contributes to the continuous increase in the number of tourists. The development of civilization causes gradually increasing interest in recreation areas with contamination-free environment. This results primarily from urbanization, changes in the structure of inhabitants in favor of mental work to improve the economic situation. A significant factor in attracting tourists to the municipality and the Bialowieza Bialowieza Forest are mainly forest areas which have natural, scenic and cultural values. Keep in mind that forest areas are for the people, but they need to be skillfully used to improve the physical and mental health, without prejudice to the principles of sustainable development. The results showed that the area of the Bialowieza Forest should aim to increase tourist attractions, improving the conditions of accommodation and ensure the efficient combination of public bus and train, to increase bicycle lanes and expansion of the base rental of recreational equipment (mainly bicycles, kayaks, equipment for Nordic walking, and winter equipment). If presented undertakings are implemented, it will definitely increase tourist traffic and at the same time it will improve the municipal budget and the budget of the families living in the community. There is also a likelihood that the stays of tourists will be longer and will be even more interest in recreation in the Bialowieza Forest. Translated by Mikolaj Jalinik

Assessment of heavy metals and crude protein content of molluscs and crustaceans from two selected cities in Nigeria

Crabs, shrimps, periwinkles and land snails form a source of aquatic food which is widely consumed in Nigeria. Therefore, there is need for comparison of nutritional information and heavy metals accumulation potentials of these organisms. The aim of this study was to quantify heavy metals (Cu, Zn, Pb and Cd) and crude protein content of these species that are sold in markets in Ibadan and Lagos, Nigeria. In addition, the influence of location, organism species, organism age, and processing on the levels of the analytes were also investigated. The results showed that mean Cu concentrations ranged from 4.88±0.54µg/g in edible land snail (Gabiella africana) to 34.1±3.0µg/g in raw guinea shrimp (Parapenaeopsis atlantica) and Zn concentrations from 21.4±1.6 in African giant snail (Archarcantina marginata) to 190±21µg/g in raw pink shrimp (Penaeus notialis). The concentration of Zn in all species was below the WHO maximum permissible limit of 100µg/g except in crabs and raw shrimps. Cu concentrations in all the samples except dry shrimps and snails were higher than the WHO permissible level of 10µg/g. Furthermore, highest Pb levels were found in crabs (Callinectes pallidus) (2.74±0.45µg/g) and the minimum mean level of 0.66±0.07µg/g was observed in G. africana. All the samples except dried shrimps contained Pb above the EC limit of 0.5µg/g. The highest mean level (0.20±0.17µg/g) of Cd was detected in crab while the least (0.03±0.01µg/g) was found in periwinkle. However, these levels were lower than the EC limit of 0.5µg/g. The concentrations of Cu, Zn, Pb and Cd in the organisms differed a little between the two sampling locations. The concentration of heavy metals (HMs) varied with studied organisms. For instance, gladiator swim crab (Callinectes pallidus) and raw pink shrimp (P. notalis) bioconcentrated remarkably higher levels of Cu, Zn, Pb and Cd than the other organisms. The process of drying significantly decreased bioavailable HMs in shrimps. Matured snails contained highest concentrations of Cu and Pb while baby snails contained highest levels of Zn. About 63% Cu, 70% Pb, 87% Zn and 10% protein content appeared to be lost during the drying process in shrimps. Crude protein contents ranged from 35.7±2.5% in crabs (C. pallidus) to 79.5±2.0% in snails (G. africana), implying that shrimps, crabs, periwinkles and snails are good sources of animal protein if they are found in contamination free environment.

Effect of the magnet insertion on the performance of a superconducting pump

For medical and semiconductor fabrication lines, an ultra-clean and impurity-free environment is often required. In order to realize such a contaminant-free environment, it is desirable to employ a completely non-contact rotating mechanism. Such a non-contact rotation is possible by using a combination of permanent magnets and bulk superconductors. Furthermore, it is necessary to rotate a superconducting pump stably for practical applications. With the aim of increasing the stiffness of rotational parts, we placed a permanent magnet at the bottom such that the superconductors are sandwiched by top and bottom magnets. It was confirmed that the stiffness could surely be improved by arranging lower permanent magnets.

Commensal microbiota modulate murine behaviors in a strictly contamination‐free environment confirmed by culture‐based methods

There is increasing evidence suggesting the existence of an interaction between commensal microbiota, the gut and the brain. The aim of this study was to examine the influence of commensal microbiota on the host behaviors in a contamination-free environment, which was verified by culture-based methods. Open-field and marble-burying tests were used to analyze anxiety-like behaviors and locomotor activity in gnotobiotic BALB/c mice with a common genetic background in a sterile isolator. The monoamine levels in several regions of the brain were measured in germfree (GF) mice and commensal fecal microbiota-associated mice (EX-GF). A 24-h exposure to the environment outside the sterile isolators rendered GF mice less anxious than those not contaminated, while there was no change in the locomotion. EX-GF mice, the gnotobiotic mice with normal specific pathogen-free microbiota, were less anxious and active than GF mice using open-field and marble-burying tests. The norepinephrine, dopamine, and serotonin turnover rates were higher in the EX-GF mice than in the GF mice in most regions of the brain, suggesting that monoaminergic neurotransmission might increase in the EX-GF mice comparing the GF mice. Monoassociation with Brautia coccoides reduced the anxiety level, but it did not affect the locomotor activity. In contrast, colonization with Bifidobacterium infantis decreased the locomotor activity, while having little effect on the anxiety level. These results strongly support the current view that gut microorganisms modulate brain development and behavior.

Beamline mirrors and monochromator for X-ray free electron laser of SACLA

Beamline mirrors and a monochromator were developed as key optical devices for the Japanese XFEL facility, SPring-8 Ångstrom Compact Free Electron Laser (SACLA). The optics were designed for transporting extremely intense, transversely coherent XFEL light to the experimental stations. The mirror system delivers a pink beam with high intensity and an energy range below 15keV, while the monochromator with Si (111) covers wider energy range of 4–30keV with 0.01% bandwidth. For realizing high stability and contamination-free environment, the mechanics of these optical components were designed to have high stiffness with ultra-high vacuum (UHV) compatibility. After 100 days of operation, no radiation damage was observed on the mirror surfaces.

Catalyst and Chirality Dependent Growth of Carbon Nanotubes Determined Through Nano‐Test Tube Chemistry

The interior of carbon nanotubes, provide a homogeneous, contaminant-free environment in which to perform nanoreactions, hence the term nano-test tubes. Here, routes for the controlled growth of carbon nanotubes with defined chiral indices are presented within the interior of single-walled carbon nanotubes upon the encapsulation of Pt and Fe catalysts, plus the carbon source in controlled proportions. Factors affecting the growth (e.g. temperature) are examined experimentally.