digestive enzymes are enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption by the body. Digestive enzymes are found in the digestive tract of animals (including humans) where they aid in the digestion of food as well as inside the cells, especially in their lysosomes where they function to maintain cellular survival.
Digestive enzymes are diverse and are found in the saliva secreted by the salivary glands, in the stomach secreted by cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the intestinal (small and large) secretions, or as part of the lining of the gastrointestinal tract.
Digestive enzymes are classified based on their target substrates:
- Proteases and peptidases split proteins into their monomers, the amino acids.
- Lipases split fat into three fatty acids and a glycerol molecule.
- Carbohydrases split carbohydrates such as starch and sugars into simple sugars such as glucose.
- Nucleases split nucleic acids into nucleotides.
In the human digestive system, the main sites of digestion are the oral cavity, the stomach, and the small intestine. Digestive enzymes are secreted by different exocrine glands including:
- Salivary glands
- Secretory cells in the stomach
- Secretory cells in the pancreas
- Secretory glands in the small intestine
discharge of pollutants into groundwater without percolation throughout the soil or subsoil.
discharge according to 76/464/EGK regulation means the introduction into the waters referred to in paragraph 1 of any substances in List I or List II of the Annex, with the exception of:
- discharges of dredgings,
- operational discharges from ships in territorial waters,
- dumping from ships in territorial waters.
1. organohalogen compounds and substances which may form such compounds in the aquatic environment,
2. organophosphorus compounds,
3. organotin compounds,
4. substances in respect of which it has been proved that they possess carcinogenic properties in or via the aquatic environment
5. mercury and its compounds,
6. cadmium and its compounds,
7. persistent mineral oils and hydrocarbons of petroleum origin,
8. persistent synthetic substances which may float, remain in suspension or sink and which may interfere with any use of the waters.
1. The following metalloids and metals and their compounds: Ag, As, B, Ba, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Se, Sn, Te, Ti, Tl, U, V, Zn,
2. Biocides and their derivatives not appearing in List I.
3. Substances which have a deleterious effect on the taste and/or smell of the products for human consumption derived from the aquatic environment,
and compounds liable to give rise to such substances in water.
4. Toxic or persistent organic compounds of silicon, and substances which may give rise to such compounds in water, excluding those which are biologically harmless or are rapidly converted in water into harmless substances. (1)Where certain substances in list II are carcinogenic, they are included in category 4 of this list.
5. Inorganic compounds of phosphorus and elemental phosphorus.
6. Non persistent mineral oils and hydrocarbons of petroleum origin.
7. Cyanides, fluorides.
8. Substances which have an adverse effect on the oxygen balance, particularly : ammonia, nitrites.
disinfectants are used against harmful bacteria and fungi. From the chemical point of view disinfectants belong to strong oxidizers or reductants, acidic or alkaline substances, solvents or surfactants. Most widely used chemical substances are the followings: active chlorine containing compounds, such as hypochlorites, chloramines, chlorine dioxide etc.);
active oxygen containing substances, such as peroxides, persulfates, perborates; strong oxidizers, such as ozone and permanganate solutions; iodine (Betadine); alcohols, most frequently 70% ethanol, propanol, isopropanol, phenolic substances such as pure phenol, cresols hexachlorophene, pentachlorophenol. Surfactants, such as some quaternary ammonium cations or chlorhexidine, can also be used as disinfectants. The use of heavy metals, such as silver, mercury and copper is restricted due to their environmental and human hazard. Concentrated strong acids (phosphoric, nitric, sulfuric, amidosulfuric, toluenesulfonic acids) and alkalis (sodium, potassium, calcium hydroxides),
such as of pH < 1 or > 13, particularly under elevated temperature (above 60°C), effectively kills bacteria and other microbes.
a system in which particles are dispersed in a continuous phase of a different composition.
A micellar solution consists of a dispersion of micelles in a solvent (most usually water). Micelles consist of aggregated molecules of the material to be dispersed surrounded by detergents (tensides).
DMU is a concept that allows the description of a product, usually in 3D, for its entire life cycle. Digital Mockup is enriched by all the activities that contribute to describing the product. The product design engineers, the manufacturing engineers, and the support engineers work together to create and manage the DMU. One of the objectives is to have an important knowledge of the future or the supported product to replace any physical prototypes with virtual ones, using 3D computer graphics techniques. As an extension it is also frequently referred to as Digital Prototyping or Virtual Prototyping. These two specific definitions refer to the production of a physical prototype, but they are part of the DMU concept. DMU allows engineers to design and configure complex products and validate their designs without ever needing to build a physical model.
Among the techniques and technologies that make this possible are:
the use of light-weight 3D models with multiple levels of detail using lightweight data structures such as JT XVL and PDF allow engineers to visualize, analyze, and interact with large amounts of product data in real-time on standard desktop computers.
direct interface to between Digital Mockups and PDM systems.
active digital mockup technology that unites the ability to visualize the assembly mockup with the ability to measure, analyze, simulate, design and redesign.
deoxi-ribonucleic acid, the chemical substance which encodes the genetic information. A polinucleotide, that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. Within the genes this information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.
Within cells, DNA is organized into long structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.
microinjection is a technique for introducing a solution of DNA into a cell using a fine microcapillary pipet.
biotechnology is the use of biological knowledge for the development of industrial processes, and the production of useful organisms and their products. The manipulation of DNA has led to a range of applications of modern biotechnology techniques. Techniques such as recombinant DNA technology and DNA identification are applied particularly in agriculture and environmental conservation.
In the following we summarise the applications of DNA technology used in natural conservation
- DNA profiles to protect animals in wild
- captive breeding programs
- control of feral pests
Dense, Nonaqueous Phase Liquid, organic contaminants denser than water and do not dissolve or mix easily with water immiscible. It forms a separate phase pools in water. The pools containing chlorinated aliphatic solvents, chlorinated benzenes and phenols, polycyclic aromatic hydrocarbons and polychlorinated compounds serve as a long-term source for dissolved contaminant plumes. It is usually not easy to locate and identify them. Some of the DNAPL compounds can migrate through the clay layers as well providing a hazard for not only the subsurface waters but for the waters in the deeper layers as well. The following technologies can be used for the treatment: in situ thermal treatment, in situ bioremediation, in situ chemical oxidation = ISCO, application of co-solvents and tenzides to dissolve the ontaminants in the ground water, than pump and treat. Without additives the remediation of DNAPL-contaminated sites by pump and treat technology is time- and cost consuming.
see omega-3 fatty acids
dopamine is a catecholamine type neurotransmitter in the brain. It has many functions in the brain, including important roles in behavior and cognition, voluntary movement, motivation, punishment and reward, inhibition of prolactin production (involved in lactation and sexual gratification), sleep, mood, attention, working memory, and learning. Dopaminergic neurons (i.e., neurons whose primary neurotransmitter is dopamine) are present chiefly in the ventral tegmental area (VTA) of the midbrain, the substantia nigra pars compacta, and the arcuate nucleus of the hypothalamus.
Dopamine can be supplied as a medication that acts on the sympathetic nervous system, producing effects such as increased heart rate and blood pressure. However, because dopamine cannot cross the blood-brain barrier, dopamine given as a drug does not directly affect the central nervous system. To increase the amount of dopamine in the brains of patients with diseases such as Parkinson's disease and dopa-responsive dystonia, L-DOPA (L-3,4-dihydroxyphenylalanine;) which is the precursor of dopamine, can be given because it can cross the blood-brain barrier.
dosage is a general term comprising the dose, its frequency and the duration of dosing. The dosage can be oral (through the mouth into the stomach), inhalation, dermal (absorption through the skin) and the test substance can be injected into the bloodstream of the test animal.
is the amount of test substance administered. Dose is expressed as weight of test substance per unit weight of test animal (e.g. mg/kg). The precise amount of test substance can be injected into the stomach or blood and under the skin.
the radiation dose is the amount of energy from radiation that is actually absorbed by the body. This is not the same as measurements of the amount of radiation in the environment.
the amount of a substance to which a person is exposed over some time period. Dose is a measurement of exposure. Dose is often expressed as milligram (amount) per kilogram (a measure of body weight) per day (a measure of time) when people eat or drink contaminated water, food, or soil. In general, the greater the dose, the greater the likelihood of an effect. An "exposure dose" is how much of a substance is encountered in the environment. An "absorbed dose" is the amount of a substance that actually got into the body through the eyes, skin, stomach, intestines, or lungs.
dose-response relationship is the relationship between the amount of exposure − given in dose − to a substance and the resulting response, the changes in body function or health.
any natural or legal person established within the community, other than the manufacturer or the importer, WHO uses a substance, either on its own or in a preparation, in the course of his industrial or professional activities. A distributor or a consumer is not a downstream user. A re-importer exempted pursuant to Article 2(7)(c) shall be regarded as a downstream user. (Source: REACH Glossary)
Dangerous Preparations Directive (1999/45/EC)
drought means the naturally occurring phenomenon that exists when precipitation has been significantly below normal recorded levels, causing serious hydrological imbalances that adversely affect land resource production systems;
Drupal is an open-source platform and content management system for building dynamic web sites. It offers a broad range of features and services including user administration, publishing workflow, discussion capabilities, news aggregation, metadata functionalities using controlled vocabularies and XML publishing for content sharing purposes. Equipped with a powerful blend of features and configurability, Drupal can support a diverse range of web projects ranging from personal weblogs to large community-driven sites.
Dangerous Substances Directive (67/548/EEC)