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Gymnosperm Wood


Gymnosperm wood is more homogeneous than that of angiosperms. Its only conducting elements are tracheids. Just like the wood of angiosperms, it is interspersed with radially orientated rays (medullary rays) consisting of parenchyma cells and sometimes also tracheids.



The wood of gymnosperms is simpler and more homogeneous than that of angiosperms. Except for the species of the order Gnetales, tracheids are the only conducting elements in gymnosperms. The most important insights into the structure and formation of pine wood that is always regarded as the prototype of gymnosperm wood stem from the German KARL SANIO (1832-1891). His observations were completed by the studies of the American botanist I. W. BAILEY (1954). SANIO assumed (1872/73) that "... the bast (phloem) and wood cells of one radial row develop from a single cell of the cambium by alternate divisions". This observation is one of the first and most important concerning the cambium's impact on secondary growth. The processes within angiosperm wood are in principal the same, but it was at first by no means simple to recognize the logical connection. Pinus silvestris or related species like the North American white pine (Pinus strobus) turned out to be ideal specimens. Pine wood is a typical object of every botanical ground course. Since cells and tissues are three-dimensional objects, they do have to be regarded from three sides to get an impression of their spatial organization:

cross-section
radial longitudinal section
tangential section.

These three perspectives can be combined in a diagram. For some years now, scanning electron microscopy has been used in the examination of the three-dimensional structure of wood.

The maybe best-known property of gymnosperm- and angiosperm wood beside the annual rings is the grain, that is visible especially nicely in tangential sections. The veneers often used in the fabrication of furniture are made from such sections.

Annual rings> are well-suited for the determination of the trees' ages. As we have already seen, their thickness depends on many factors. During the 1980th, the 14C method has been established. It is based on the fact that in every carbon-containing compound (like lignin) not only the normal carbon isotope 12C is found, but also, in much lower amounts, the radioactive isotope 14C. The 14C/12C ratio of the atmosphere is 1:106. 14C has a half-life of 5770 years. No new carbon is incorporated into an already finished compound so that its 14C content sinks continuously. The ratio of 14C/12C shifts thus in favour of 12C. Some several thousand year old Californian Sequoia- and Pinus aristata-trees turned out to be the ideal specimen to test the precision of both methods and to calibrate one with the help of the other.

The xylem of gymnosperms has few or no parenchyma cells at all. Their existence (or non-existence) is a feature of certain genera. With Pinus, they are found only in the epithelia of resin ducts, with many Podocarpaceae, Taxodiaceae and Cupressaceae (cypresses), they are amply present, while they are missing completely with Araucariaceae and Taxaceae (yews).

The tracheids of gymnosperms are 0.5-11 mm long and are orientated along the shoot or root axis. They border at neighbouring tracheids above and below not with their final walls, but with the ends of their lateral walls. This is the reason, why there are never, neither in tracheids nor in vessels, ideal, vertical conducting tubes.

In many species, it is distinguished between sapwood and heartwood. Sapwood is an active, water-conducting tissue, while heartwood is inactive and has only supporting functions. Its cells contain but little water or reserve compounds. Instead, organic compounds, oils, rubber, resins, tannic acids, dyes or aromatic compounds are stored here. Oxidized phenolic compounds give the wood a dark colour. The typical heartwood is missing in spruce (Picea excelsa), pine (Abies alba) and in some angiosperms (poplar, willow). These woods are regarded as less valuable by the timber industry than heartwood-containing ones.

Medullary rays Wood is at regular distances interspersed with radially orientated parenchyma cells and often also with tracheids. They spring from the ray initials> of the cambium. The medullary rays of conifer wood are normally only one cell layer thick, but they can be as high as 1-20 (sometimes even up to 50) layers of cells. Ray tracheids and axially orientated tracheids are connected via pits. Medullary rays with resin ducts seem spindly in tangential sections. Resin ducts can be either axially or radially orientated. There is actually hardly any difference between them and intercellular spaces that have been enlarged by the splaying of parenchyma cells. Consequently, resin ducts are always lined with parenchyma cells. Their existence has different reasons: injuries by frost or winter damages are some factors that stimulate their formation. The respective gymnosperm families react differently to these disturbances.

+ نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 14:5  توسط abdolla zamani  | 

WOOD & HERBACEOUS STEM ANATOMY

WOOD: secondary xylem - water transport & strengthening tissue made up of specialized cells with thick inner walls
MORPHOLOGY
    Bark
      cork
      cortex
      endodermis
    Phloem
    2o Cambium
      phloem
      xylem
      (1o elongation: shoots, twig tips)
    Pith
    Rays

    2o Xylem (wood)
      Sections:
        Radial
        Tangential
        Cross-section
      Rings
        Early Wood
          less dense, lumina wider, walls thinner
        Late Wood
          dense, relatively thick walls
        Transition: abrupt, gradual



CONIFER WOOD "softwoods"

    Non-Porous: without vessels
    Water Transport by Tracheids
      resin canals (i.e. radial canals [also: axial, traumatic])
        e.g., Larix, Pinus, Picea, Pseudotsuga
      without resin canals
        e.g., Abies, Calocedrus, Sequoia
    Tracheids:
      Border Pits

      Spiral Thickenings
      Cracks
    Rays
      Fusiform (with resin canal)
      Uniseriate
      Parenchyma (heterogenous)
        upright, procumbent
      Ray Tracheids
        thickened walls, slanting ends, ± teeth
        ± Nodular Endwalls ( & parenchyma)
      Cross-Field Pitting: rays X parenchyma
        Cell Wall



ANGIOSPERM WOOD "Hardwoods"

    Porous: with vessels (trachea)
    Diffuse Porous
      vessels scattered throughout annual rings
      and/or uniform in size
      e.g., Tilia, Juglans, Betula
    Ring Porous
      vessels collected in one part of ring
      and/or larger in early wood
      e.g., Fraxinus, Quercus, Ulmus
    Vessel ends
      Open Fagus

      Sieve Plates Liriodendron scalariform
    Pits (between vessels)
      Scalariform Magnolia elongate, spiral
      Opposite Liriodendron round, rows
      Alternate Acer, Populus
    Rays (parenchyma)
      Uniseriate, multiseriate
      homogeneous
      heterogenous (upright, procumbent)
    Parenchyma
      Paratrachial (associated with vessels)
        Scanty Acer
        Vasicentric Morus
        Aliform Fraxinus
        Banded Confluent
        Boundary
        Terminal Populus
      Apotrachial (not surrounding vessels)
        diffuse e.g., Quercus
        banded e.g., Tilia
          Tyloses: outgrowth of parenchyma cell into vessel, forming partial or complete blockage of lumen



HERBACEOUS STEM

GENERAL ANATOMY
    Wood absent: Vascular bundles scattered in cortex of stem.
Tissue Systems
    Dermal
      Epidermis, Stomata, Cuticle, Collenchyma
    Fascicular, Vascular
      Vascular Bundles (see types below)
        Phloem, Cambium, Xylem
      Interfascicular Region
    Fundamental
      Cortex
      Pith: Starch, Sheath, Endodermis, Casparian Strips (occasional)
Arrangement of Vascular Bundles (herbaceous and 2o woody)
    Conifers and Angiosperms
      Vascular Ring between Cortex and Pith
    Monocotyledons
    • Two Vascular Rings: Avena, Hordeum, Secale, Triticum, Oryza
    • Scattered Vasc. Bundles: Bambusa, Saccharum, Sorgum, Zea
    • Also: outer ring embedded in sclerenchyma Layer
    Vines: wide rays (=interfascicular) with bands of perivascular fibers
Types of Vascular Bundles
  • Collateral Phloem (Phloem outside xylem): most common
  • Bicollateral Phloem (Phloem both sides): Apocynaceae, Asclepiadaceae, Convovulaceae, Cucurbitaceae, Solanaceae, some Compositae
  • Amphicribal Bundles (Phloem around Xylem): Ferns, some Angiosperms
  • Amphivasal Bundles (Xylem around Phloem): Rheum, Rumex, Mesembryanthemum, Begonia, Araceae, Liliaceae, Juncaceae, Cyperaceae
  • Alternating layers of Xylem and Phloem: Amaranthaceae, Chenopodiaceae, Menispermaceae, Nyctaginaceae



TYPES TO TELL APART
Abies
Juniperus
Pinus
Fraxinus
Quercus


Conifer Wood

    Cross Section

    Radial Section

    Tanjential Section


    Juniperus sp.


    Pinus flexilis


    Pinus ponderosa


    Abies lasiocarpa



    Angiosperm Wood

    Fraxinus
    Juglans
    Quercus
    Ulmus
    Tilia



    Herbaceous Stem

      Cucurbita
      Zea

    Acacia willardiana rachis vascular bundle

    Fouquieria vascular bundle

    Fouquieria sclerenchyma bundle

    References

    Links:

    Jefferson Patterson Park and Museum fresh & charcoal

    UofAz Wood Sections http://www.geo.arizona.edu/palynology/geos581/woodsectn.html

    Crow Canyon Karen Adams
    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 14:3  توسط abdolla zamani  | 

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:59  توسط abdolla zamani  | 

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:55  توسط abdolla zamani  | 

    Chapter three The Gross Features of wood  (6h)

     

    1. The three standard Sections

        Cross Section
        Radial section
        Tangential Section

     

    2. Growth increments

       Growth ring & annual ring
       Earlywood & latewood
       False rings
       Appearance of annual rings on 3 different sections

     

    3. Sapwood & heartwood

       Conception
       Formation of heartwood
       Main differences between sapwood and heartwood

     

    4. Wood rays

       Appearance of wood rays
             on 3 different sections
       Functions of wood rays
             Radial conduction
             Storage of reserved food
             Strengthening in transverse

    5. Wood parenchyma

       Ray parenchyma
       Epithelial parenchyma
       Longitudial parenchyma

     

     

    6. Pores

       Conception
       Main difference between softwood & hardwood
       Arrangement patterns of pores

     

     

    7. Resin canals

       Normal resin canals
            Structure
            Functions
            Wood species in China

     

    --Pinus
    --Picea
    --Cathaya
    --Larix
    --Pseudotsuga
    --Keteleeria

     

       Traumatic resin canals
            Formation
            Appearance
     

    8. Texture and grain

       Texture
            Definition
            All the kinds of terms on wood texture
       Grain
            Definition
            All the kinds of terms on wood grain

    9. Figure of wood

       Definition:
            Any distinctive markings on wood surface
       All kinds of wood figure of highly decorative:

     

     

    10. Color of wood

       Formation
           Extractives
           Fungi attack
           Chemicals
           Dyes
       Color variation of wood
       Practical value of wood color

    11. Other physical properties valuable in identification

       Luster: Definition, variation , practical value
       Order: tested with nose
       Taste: tested with tongue
       Weight: light, middle, heavy
       Hardness

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:48  توسط abdolla zamani  | 


    Which tree produced the Baltic amber resin?

    Sorry, but a still rough English translation follows!

    Debris of wood are very abundant in amber, though not liked by collectors. What is still recognizable, are splinters of coniferous wood. I do not know any rsplinters of angiosperm wood in Baltic (and Bitterfeld) amber! Most of those wood debris are the result of activity of insects resp. insect larvas. Therefore these wood debris flown out with the streaming resin are the most abundant and important remains of the amber trees.
    Which other parts of the amber coniferous trees could have got into the resin and remain enclosed in it? Parts of bark, if not too large; pollen dust; male flower buds or parts of it, needles resp. leaves - bigger parts like cones derived form female flowers do not remain stucked to the resind and will not be enclosed completely.
    But there seem obvious contradictions: wood and pollen grains looks like pine, but the chemistry of the amber looks like resin from araucarias, and needles resp. gymnosperm leaves are much less included as normally expected.
    • Concerning the resin chemistry, there are newer dicovery results about the fact that resins change so much during and after becoming amber, that they are comparable to species of living trees only in a very restricted manner. Except of that. at least one of the still living pine species, which has a resin composition very different from the rest of pines and has some similarities to Baltic amber. So resin chemistry appears to be not so well suited to identify the amber tree. Angiosperm resins like Doninican and Mexican amber can be excluded at least. (Between Baltic amber however, there can be found some rare pieces representing fossil resins coming form other plants than normal.)
    • The majority of flower dust (pollen) is most similar to pine pollen. Also the parts of male flowers, which are not so rare in amber, seem to represent pines. But also much pollen of gymnosperm and angiosperm trees and brushes is found in amber, representing plants which grew in the vicinity of the amber trees, but produced no resin at all.
    • Leaves and needles in amber lead to a curious impression: Small elongated gymnosperm leaves are not seldom, but they derive certainly not from pines. Other leaves come from thuja or cypress plants. Needles and its remains are rarely enclosed in amber, and they are diverse, part of them representing more fir (abies) needles. Possibly the amber tree had needles so long as the Canarian pine or the Caribic swamp pine, which have nearly no chance of preservtion in amber because of its length. Pieces of bark with its characteristic cork tissue are not rare, but can come from any conifer.
    • First of all let us have a look at a microscopic sketch of typical Baltic amber wood:
    Reconstruction sketch of amber wood, changed by me after a Vorlage from R. Wagenführ. Direction of growth from the interior (front left) to the exterior (behind right) according to the arrow. A bit more than one year's groths is shown.

    Above: Cross section with resin channel (yellow) and wood ray (brown). The early wood consisting of broad longitudinal tracheids is light coloured, the late wood darker ("quer" means cross-section).

     Tangential view with wood rays, one of them with a resin channel. Brown: wood ray parenchym cells, blue: transverse tracheids as components of the wood rays.

     Radial view with a wood ray consisting of parenchym cells (living storage cells, brown) with simple pits and of two transverse tracheids (blue) with small bordered pits. The longitudinal tracheids (vertical) of the early wood (lighter) have big round bordered pits.

    Continue to: Wood remains in Baltic and Bitterfeld amber (1)     Back
      Too much technical terms? No idea, how active gymnosperm wood "works"? So I will try to give some general explanations (wood specialists may forgive me for my simplifications!)

      Gymnosperms are a plant class consisting of cycads, ginkos, yewtrees (taxus), thujas, cypresses, redwoods and conifers. Gymnosperm wood has no continuous vessels (trachees), but extremely elongated vessel cells (longitudinal tracheids), which are situated vertically in a tree trunk and which are used for transporting liquids and nutritional solutions together with parts of the bark except they have become part of the core wood. The upper most part of gymnosperm wood consists of tracheids. Its more or less massive walls are responsible for the strength of the wood.

     
    A tracheid is a very elongated cell, but closed on all sides - how can it help to transport liquids? Tracheids are dead cells - its contents are decomposed, they are so to speak empty. But they are connected to the neighbouring cells by so-called "pits", better by pairs of pits. A pit is an area of the cellular wall so thin that liquids resp. nutritional solutions can pass. Towards neighbouring tracheids, bordered pits (sketch left) are formed, both tracheids forming one half of the pit pair (red and green). A thickened section (torus) in the center of the membrane may shut the bordered pit constantly or temporary under certain circumstances. To the right, a simple pit pair as usual beteeen living cells (according to Wagenführ, modified).
      So far, transport and compensation of liquids is guaranteed in a concentric ring of neighouring tracheids. But in coniferous wood with resin channels like amber wood there are no pit connections between such a ring of tracheids to the next older (inner) or to the next younger (outer) ring of tracheids - therefore there are no pits in the tangential view in the sketch above. The liquid compensation between the inner and the outer tracheids is managed by parts of the wood rays, which wise transverse to the longitudinal tracheids from the center outwards (sketch above). If the coniferous wood has resin channels, the wood ray consists of transverse tracheids and wood ray parenchym cells which are alive and able to store nutritional substances.

      Normally the outermost cells of a wood ray are transverse tracheids. Like the longitudinal tracheids, they are dead cells and according to that they have (small) bordered pits. In many pines, but not in amber wood, the transverse tracheids have conspicuously jagged membranes. In gymnosperm wood without transverse tracheids, the longitudinal tracheids bear some bordered pits also on its tangential sides, so that a liquid regualtion between the different rings of tracheids can take place.

      Wood ray parenchym cells are living cells with plasma and core. They are connected to each other and to the tracheids by simple pits (not bordered pits). Even in amber the darker colour of those parenchym cells is visible occasionally, possibly caused by deposited nutritional substances.

      There are vertical resin channels between the tracheids and horizontal ones within thicker woodrays consisting of several layers. Resin channels are surrounded by special cells producing resin

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:44  توسط abdolla zamani  | 

    Looking inside bones, teeth and wood

    last modified 25-09-2006 17:22

    Have you ever wondered how teeth can resist all kinds of constraints up to the late stages of our lives? Or why trees grow high and don't break despite meteorological events such as strong winds and storms? Or what happens to bones and how they look like in illnesses such as osteoporosis? All these questions had their answers in last week's seminar "Hierarchical structure of wood, bone and tooth - scanning x-ray microdiffraction studies" by Dr. Peter Fratzl, a material scientist from the Austrian Academy of Sciences. He comes regularly to the ESRF for these studies, on ID13, the microfocus beamline.

    You may ask yourself what do bones, teeth and wood have in common. These three items have a hierarchical structure that offers a very different image of them depending on how close you observe them. In this sense, if we look deep inside we discover cellular structures that contain fibre composites.

    The methods used to study these structures at the ESRF are small angle
    X-ray scattering and scanning X-ray microdiffraction. These techniques are able to cover two scales simultaneously: the nanometre scale by the analysis of the diffraction patterns, and the micrometre scale by scanning the sample across the X-ray beam, which is a few micrometres wide.

    Combined with nanoindentation, which provides information about the mechanical properties of the sample, this kind of research can have many applications.

    In the domain of bone structure, researchers study the evolution of bones through age (throughout one's lifetime, old bone is removed -resorption- and new bone is added to the skeleton -formation-). Thanks to the high resolution of the images they obtain, scientists test different treatments against illnesses such as osteoporosis (when bone resorption occurs too quickly or if replacement occurs too slowly) or Osteogenesis Imperfecta, most known as "brittle bone disease". In the case of wood, it is useful for wood industry to know where the tree is more stiff and where it is more flexible. The study on the tooth has shown that its properties are graded in order to have a better long-term stability against failure of the tooth. Since teeth have proved to be very resistant materials, engineers try to copy their structure in artificially created materials.

       


    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:35  توسط abdolla zamani  | 

    The structure of wood

    Wood cells

    The parallel cellulose polymers (right corner) are held together by cross-linking hemicellulose and some lignin to form fibrils, which provide mechanical strength and stability to the wood. The cell wall is a layered structure around the lumen, the empty space where the protoplasm has been located (see below), with a middle lamella (ML) and primary wall (P) in the outer part. The secondary wall is mainly for support and comprises primarily cellulose and lignin. Often one can distinguish three distinct layers, S1, S2 and S3, which differ in the orientation of the cellulose fibrils. The cell wall is built up in a similar way as a tire that has a series of steel cords embedded in an amorphous matrix of rubber. In the plant cell wall, the "cords" are analogous to the cellulose fibrils and they provide the structural strength of the wall. The rubber in the tire corresponds to non-cellulosic cell wall components, see: http://employees.csbsju.edu/ssaupe/biol327/Lecture/cell-wall.htm; http://sunflower.bio.indiana.edu/~rhangart/courses/b373/lecturenotes/cellwall/cellwall.html.

    The scanning electron microscope (SEM) pictures (below) show cell walls around large lumen in marine archaeological oakwood with somewhat degraded S2 layers. The arrow indicates the lignin-rich middle lamella (ML) holding the cell walls together. In the lower picture a pyrite (FeS2) particle is visible.

    SEM

    Acid in wood

    The cellulose polymer consists of linked glucose rings, usually about 10 000 subunits. An oxygen atom between the carbon atoms 1 and 4 joins the rings. These so-called glycoside linkages are easily broken (hydrolysed) in an acid environment, while fairly stable under neutral and alkaline conditions. The catalytic degradation is initiated by a hydronium ion (H3O+), binding to the bridging oxygen atom. This facilitates breaking of the bond between the oxygen and carbon atom 1. When a water molecule then binds to carbon atom 1, a hydronium ion is regenerated and can initiate a new hydrolysis reaction. The length of the cellulose chain will gradually decrease. Finally only small fragments of crystalline cellulose of about 200 glucose units will remain, and the tensile strength of the wood will have completely disappeared (Johansson 2000).

    Cellulose

    How fast and far the Vasa's wood deteriorates in the museum environment has yet to be investigated, however. The rate depends not only on pH but also on temperature, humidity, presence of iron compounds and possibly other factors. The presently accumulated amount of sulfuric acid in the wood is estimated to about 2 tonnes, and additionally 5-6 tonnes may form if the remaining sulfur will become fully oxidized. The acid is forming continuously, and higher acidity will increase the rate of cellulose degradation in the wood. The bicarbonate/soda treatment of the Vasa's wood surfaces has only a temporary and insufficient effect, and it is important to develop and apply better methods. The large amount of sulfur in the hidden surfaces under planking and dunnage is a difficult problem for efficient treatment.

    Further research and treatment

    Our discoveries about accumulation of reduced sulfur compounds in waterlogged wood showed the need for further insight in the requirements for lasting conservation treatments. However, experience shows that the long-term consequences of new conservation procedures must be carefully investigated to avoid future problems. In December 2002 the National Maritime Museums (NMM) invited applications from scientists interested in taking part in a research project on the Vasa and sulfur. The sum of eight million Swedish kronor spread over four years was put up by five funding bodies: the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, the National Heritage Board, the Bank of Sweden Tercentenary Foundation, the Swedish Foundation for Strategic Research, and the Swedish Agency for Innovation Systems. Five research teams were selected in October 2003 to work on a project to find a long-term solution to the Vasa’s sulfur problems. Professor Emeritus Lars Ivar Elding of the University of Lund coordinates scientific and economic aspects of the NMM based project. Eight million Swedish kronor will be spent over four years on wide-ranging scientific studies aimed at halting the breakdown of the ship’s timber, see: http://www.vasamuseet.se/Vasamuseet/Verksamhet%20och%20Projekt/Bred%20forskning.aspx?lang=en.

    The continued work is directed toward developing scientifically based treatment methods for the Vasa, which also will be of interest for other marine archaeological artefacts.  Nowadays, there can be no doubt that the Vasa's significance historically, culturally, and also economically, is so great that all necessary efforts should be made. An interesting comment regarding the exorbitant costs to maintain and conserve artefacts and materials recovered from an underwater environment, was made in the Guidelines to the American Abandoned Shipwreck Act i US law from 1988, see : "The best example is in Sweden, where sufficient public and private funds were made available to document, raise, maintain, conserve, interpret, and exhibit the intact 17th century Swedish warship Vasa. Revenues generated annually into the Swedish economy by tourists visiting the Vasa are said to be $275 million"!

     The following questions are being investigated within the Save the Vasa project:

    • what are the factors/substances that accelerate the oxidation and decomposition processes and how can these be removed or be made inactive?
    • what methods can be developed to remove the acid formed and to prevent/delay continued acid formation?
    • how rapidly and in what way do acid and iron compounds cause decomposition of the wood in the current circumstances?
    • how can the iron compounds in the wood of the Vasa be removed or deactivated? This includes finding a suitable inert material to replace existing bolts where this is possible.
    • how can the stability and decomposition of polyethylene glycol be characterised and what is the possibility of reinforcing the conservation protection? This includes investigating the interplay between wood, iron and PEG under the conditions that prevail in the Vasa and identifying the decomposition products of the polyethylene glycol.

    Other important tasks connected to the preservation of the Vasa is the installation of a more efficient climate control system for the exhibition hall of the Vasa Museum, which was completed in 2004, and the construction of a special cradle that supports and distributes the Vasa's weight better. A better cradle can prevent the hull from subsiding even more, and can also facilitate the exchange of the bolts and other conservation treatments involving partial dismantling. An advanced laser positioning system, designed by the Department of Geodesy and Photogrammetry, KTH, is already installed and shows the tiniest movements in the hull of the Vasa. The system is very valuable for monitoring movements when changing bolts and dismantling parts of the hull, and will reveal subsiding if the mechanical strength of the wood gradually decreases. The coordination between the research work, the development and testing of the devised conservation procedures, and their actual application to the Vasa, will be very important and will certainly extend over a long period of time.

    Final comments

    Because of our scientific collaboration and the fortunate availability of new analytical techniques, the causes of the problems were discovered at an early stage, which provided time to develop cures and take appropriate actions. The robust construction of the Vasa, with massive timbers in carrying parts, ensures that the danger is not immediate. Despite the large weight of the hull, no alarming structural damage is yet apparent. Nevertheless, the sooner an appropriate treatment of the Vasa can begin, the better. The work will probably be a constant struggle against the ravages of time and acid, but the Vasa is well worth all efforts. The Vasa may be under acid attack, but she will prevail in her first real battle!

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:32  توسط abdolla zamani  | 

    The structure of wood

    Wood cells

    The parallel cellulose polymers (right corner) are held together by cross-linking hemicellulose and some lignin to form fibrils, which provide mechanical strength and stability to the wood. The cell wall is a layered structure around the lumen, the empty space where the protoplasm has been located (see below), with a middle lamella (ML) and primary wall (P) in the outer part. The secondary wall is mainly for support and comprises primarily cellulose and lignin. Often one can distinguish three distinct layers, S1, S2 and S3, which differ in the orientation of the cellulose fibrils. The cell wall is built up in a similar way as a tire that has a series of steel cords embedded in an amorphous matrix of rubber. In the plant cell wall, the "cords" are analogous to the cellulose fibrils and they provide the structural strength of the wall. The rubber in the tire corresponds to non-cellulosic cell wall components, see: http://employees.csbsju.edu/ssaupe/biol327/Lecture/cell-wall.htm; http://sunflower.bio.indiana.edu/~rhangart/courses/b373/lecturenotes/cellwall/cellwall.html.

    The scanning electron microscope (SEM) pictures (below) show cell walls around large lumen in marine archaeological oakwood with somewhat degraded S2 layers. The arrow indicates the lignin-rich middle lamella (ML) holding the cell walls together. In the lower picture a pyrite (FeS2) particle is visible.

    SEM

    Acid in wood

    The cellulose polymer consists of linked glucose rings, usually about 10 000 subunits. An oxygen atom between the carbon atoms 1 and 4 joins the rings. These so-called glycoside linkages are easily broken (hydrolysed) in an acid environment, while fairly stable under neutral and alkaline conditions. The catalytic degradation is initiated by a hydronium ion (H3O+), binding to the bridging oxygen atom. This facilitates breaking of the bond between the oxygen and carbon atom 1. When a water molecule then binds to carbon atom 1, a hydronium ion is regenerated and can initiate a new hydrolysis reaction. The length of the cellulose chain will gradually decrease. Finally only small fragments of crystalline cellulose of about 200 glucose units will remain, and the tensile strength of the wood will have completely disappeared (Johansson 2000).

    Cellulose

    How fast and far the Vasa's wood deteriorates in the museum environment has yet to be investigated, however. The rate depends not only on pH but also on temperature, humidity, presence of iron compounds and possibly other factors. The presently accumulated amount of sulfuric acid in the wood is estimated to about 2 tonnes, and additionally 5-6 tonnes may form if the remaining sulfur will become fully oxidized. The acid is forming continuously, and higher acidity will increase the rate of cellulose degradation in the wood. The bicarbonate/soda treatment of the Vasa's wood surfaces has only a temporary and insufficient effect, and it is important to develop and apply better methods. The large amount of sulfur in the hidden surfaces under planking and dunnage is a difficult problem for efficient treatment.

    Further research and treatment

    Our discoveries about accumulation of reduced sulfur compounds in waterlogged wood showed the need for further insight in the requirements for lasting conservation treatments. However, experience shows that the long-term consequences of new conservation procedures must be carefully investigated to avoid future problems. In December 2002 the National Maritime Museums (NMM) invited applications from scientists interested in taking part in a research project on the Vasa and sulfur. The sum of eight million Swedish kronor spread over four years was put up by five funding bodies: the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, the National Heritage Board, the Bank of Sweden Tercentenary Foundation, the Swedish Foundation for Strategic Research, and the Swedish Agency for Innovation Systems. Five research teams were selected in October 2003 to work on a project to find a long-term solution to the Vasa’s sulfur problems. Professor Emeritus Lars Ivar Elding of the University of Lund coordinates scientific and economic aspects of the NMM based project. Eight million Swedish kronor will be spent over four years on wide-ranging scientific studies aimed at halting the breakdown of the ship’s timber, see: http://www.vasamuseet.se/Vasamuseet/Verksamhet%20och%20Projekt/Bred%20forskning.aspx?lang=en.

    The continued work is directed toward developing scientifically based treatment methods for the Vasa, which also will be of interest for other marine archaeological artefacts.  Nowadays, there can be no doubt that the Vasa's significance historically, culturally, and also economically, is so great that all necessary efforts should be made. An interesting comment regarding the exorbitant costs to maintain and conserve artefacts and materials recovered from an underwater environment, was made in the Guidelines to the American Abandoned Shipwreck Act i US law from 1988, see : "The best example is in Sweden, where sufficient public and private funds were made available to document, raise, maintain, conserve, interpret, and exhibit the intact 17th century Swedish warship Vasa. Revenues generated annually into the Swedish economy by tourists visiting the Vasa are said to be $275 million"!

     The following questions are being investigated within the Save the Vasa project:

    • what are the factors/substances that accelerate the oxidation and decomposition processes and how can these be removed or be made inactive?
    • what methods can be developed to remove the acid formed and to prevent/delay continued acid formation?
    • how rapidly and in what way do acid and iron compounds cause decomposition of the wood in the current circumstances?
    • how can the iron compounds in the wood of the Vasa be removed or deactivated? This includes finding a suitable inert material to replace existing bolts where this is possible.
    • how can the stability and decomposition of polyethylene glycol be characterised and what is the possibility of reinforcing the conservation protection? This includes investigating the interplay between wood, iron and PEG under the conditions that prevail in the Vasa and identifying the decomposition products of the polyethylene glycol.

    Other important tasks connected to the preservation of the Vasa is the installation of a more efficient climate control system for the exhibition hall of the Vasa Museum, which was completed in 2004, and the construction of a special cradle that supports and distributes the Vasa's weight better. A better cradle can prevent the hull from subsiding even more, and can also facilitate the exchange of the bolts and other conservation treatments involving partial dismantling. An advanced laser positioning system, designed by the Department of Geodesy and Photogrammetry, KTH, is already installed and shows the tiniest movements in the hull of the Vasa. The system is very valuable for monitoring movements when changing bolts and dismantling parts of the hull, and will reveal subsiding if the mechanical strength of the wood gradually decreases. The coordination between the research work, the development and testing of the devised conservation procedures, and their actual application to the Vasa, will be very important and will certainly extend over a long period of time.

    Final comments

    Because of our scientific collaboration and the fortunate availability of new analytical techniques, the causes of the problems were discovered at an early stage, which provided time to develop cures and take appropriate actions. The robust construction of the Vasa, with massive timbers in carrying parts, ensures that the danger is not immediate. Despite the large weight of the hull, no alarming structural damage is yet apparent. Nevertheless, the sooner an appropriate treatment of the Vasa can begin, the better. The work will probably be a constant struggle against the ravages of time and acid, but the Vasa is well worth all efforts. The Vasa may be under acid attack, but she will prevail in her first real battle!

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:31  توسط abdolla zamani  | 

    Composites 101

    The purpose of this link is to educate the reader on composites, and why they are a compelling alternative to wood.  Composites work very well with wood, or can replace wood if needed.

    The word “composite” means two or more materials combined to form a composite material.  Fiber reinforced materials, commonly referred to as composites, have been around for centuries.  Early settlers found that by combining straw with mud, the composite was much stronger.  Highways and bridges are composite because of the steel rebar embedded in the concrete.  In today’s modern age, light weight composites in the form of fiber reinforced resins have become the standard in sporting goods and aerospace applications.

    Modern composite materials use high strength fibers made from a variety of materials such as fiberglass, carbon, aramid, boron, and others.  The most popular is carbon fiber, due to its high stiffness, high strength, and light weight.  Carbon fibers may be manufactured from polyacrylonitrile (PAN), pitch, or rayon precursor materials by high-temperature (2000 to 35000 F) carbonization or graphitization processes, hence the name “graphite.”

    Carbon fiber is useless without a resin binder.  Typically, carbon fibers are coated with an epoxy resin which surrounds the fibers and holds them in place.  This material is known as a prepreg, which stands for “pre-impregnated” meaning the fibers have been embedded into the epoxy resin.

    Carbon fiber is useless without a resin binder.  Typically, carbon fibers are coated with an epoxy resin which surrounds the fibers and holds them in place.  This material is known as a prepreg, which stands for “pre-impregnated” meaning the fibers have been embedded into the epoxy resin.

     

    With prepreg materials, the carbon fibers are unidirectional, meaning all the fibers run in the same direction parallel to each other.  This is the most efficient arrangement of fibers.  At FiberSonixx, we take the prepreg sheets and cut them to different shapes and at different fiber angles to create a “lay-up” specific to each individual product.  For example, we can change the stiffness of a neck by simply changing the fiber angle.  We can also combine different fibers to create a hybrid composite, which has beneficial properties of both.  In addition, once the recipe is optimized  the composite structure is repeatable part after part, ensuring consistent high quality time after time.
     

     

    This is what an ideal composite structure looks like up close, magnified 500X.  The fibers should be distributed in the resin matrix uniformly.  This allows the matrix material to transfer the load to the fibers in a uniform manner, resulting in an efficient structure. 

     

     

    Wood has a fiber structure very similar to a composite material.  Wood is comprised of a fibrous structure of cellulose, which has a grain to it where the wood is stronger in one direction than another.  This is because the cellulose fibers are parallel to each other, much in the same way unidirectional composites are formed.

     

      

     
    Wood comes in a variety of species, all which have different grain structures, densities, strengths, and beauty.  Even the same species of wood varies based on growing conditions.  Furthermore, within the same tree, the properties of wood can vary.  Despite these inconsistencies, wood is an excellent material for musical instruments, but has limitations:

    -wood is a natural material, meaning that variance can occur from batch to batch.  Trees grow at different rates depending on weather, so every batch can be different.

    -wood is affected by moisture, so factories must treat the wood and store in temperature and moisture controlled environments while manufacturing the product.  Once the product is shipped, it remains susceptible to these environmental conditions, which can cause the wood to warp, crack, and change dimension.

    -wood can expand and contract with temperature and moisture, effecting the production of wood parts, and affecting the sound of musical instruments.  It is easy to see why wood instruments require constant tuning.

    -the fiber orientation of wood is limited to what nature gives us.  It is possible to create a laminate of different plies of wood at different grain orientations (e.g. plywood) but the above deficiencies still exist.

    At FiberSonixx, we can design in the exact tone desired by changing the stiffness and weight of the component.  Sound travels through a structure as a function of stiffness and weight, so it is possible to “dial in” the optimal combination for every application.  With fiber reinforced composites, there are numerous ways to adjust the tone of the product:

    -type of fiber used:  we can use very stiff and light carbon fibers, or heavier and more flexible glass fibers, or a combination of each to optimize the performance and cost

    -orientation of fiber angles:  a low angle like 0 degrees maximizes stiffness, where an intermediate angle such as 45 degrees is much more flexible.

    -stacking sequence:  as different plies are stacked up creating the layup, the sequence and location of each fiber type can affect the stiffness and tone.

    -different resin systems:  we can use a strong resin such as epoxy, which will produce good attack and sustain, or use a softer resin like a thermoplastic, which will produce a warmer tone.

    The world of composites offers unlimited options to optimize the performance of a musical instrument.  They can be used alone or in combination with wood, to take advantage of the best parts of both.
     

    + نوشته شده در  چهارشنبه هجدهم آذر 1388ساعت 13:28  توسط abdolla zamani  | 

    MDF چیست؟

    (Medium Dencity Fibernation) مخفف MDF است.

    MDF فیبر با چگالی متوسط  است که بصورت فشرده از ضایعات چوب تهیه می گردد و از مقاومت زیادی در مقابل رطوبت برخوردار است. MDFهمواره به عنوان مغز و درون کار در صنعت چوب مورد استفاده قرار می گیرد. آنچه MDF را زیبا می سازد پوشش روی آن است که بسته به نوع کارمتفاوت می باشد. از معروفترین روکشهای MDF می توان PVC ، VINILIUM، HPL وفرمیکا را نام برد. لازم به ذ کر است فرمیکا بسته به نوع ضخامتش متفاوت می باشد. بنابراین هرچه از روکشهای ضخیمتر و مقاومتر در پوشش MDF استفاده شود جنس مرغوبتری بدست خواهد آمد.

    panouri mdf MDF چیست؟

    MDF چیست:

    MDF نوعی فیبر است که از خرده چوب بهم فشرده تحت فشار و حرارت به وجودمی آید.

    اکنون در بیشتر موارد سازندگان کابینت از MDF به جای تخته سه لائی یا تخته های نئوپان استفاده می کنند.

    1. چگال بودن MDF ، یعنی زیاد بودن ذرات چوب در واحد حجم آن، محکم و بدون گره بودن این نوع فیبر که به سوراخ کاری و سوهان کاری آن و ایجاد فرم های دلخواه کمک می کند.
    2. سطح آن هموار است.
    3. وجود ذرات بسیار ریز و نرم ، بافت غیر قابل تشخیصی دارد.
    4. این نوع فیبر براحتی با چسب چوب به هم می چسبد،
    5. سطح آن را می توان رنگ روغن یا رنگ پلاستیک زد و همچنین با لترون یا اچ پی ال یا ملامین روکش کرد.
    6. نسبت به اب مقاومت بیشتری دارد.

    MDF در ساخت کابینت، دیوارهای چوبی، کمد و دکوراسیون داخلی منازل استفاده می شود.

    fasady2 MDF چیست؟

    مشخصات: ,

    • Imported Products
      Bed Sets
      Sofa Sets
      Dining Sets
      TV Stands
    + نوشته شده در  یکشنبه هشتم آذر 1388ساعت 16:10  توسط abdolla zamani  | 

    آشنایی با انواع چوب

    توسکا: Alnus

    دو گونه توسکای قشلاقی و ییلاقی به نام های علمی Alnus subcordate و glutionose alnus درایران وجود دارد.نام های محلی توسکا،تسکا و توسه است.چوب درون نامشخص ،رنگ کرم مایل به قرمز،دوایر سالیانه پهن با حدودنسبتا”مشخص و موجدار درمقطع عرضی وپره چوبی آجری شکل قرمز در مقطع شعاعی و دوک های ظریف(پره ها)در مقطع مماسی ازخصوصیات ظاهری چوب است.

    چوبی نیمه سنگین تا سبک است که به دلیل پراخت و رنگ پذیری شکاف خوری و ابزار خوری خوبدر صنعت مبلمان مصرف دارد ولی کم دوام بوده که البته در آب دوام قابل توجهی دارد.بیشترین میزانفروش را در بازار چوب فروشان پس از راش را داراستو که البته در حال حاضر مهمترین ورد مصرفآن طبق امار موجود در کارخانه جات تخته لایه سازی آن در برابر آب در ساختن بناهای آبی نیز مصرف می شود قیمت چوب توسکا به صورت الواری در سال بوده است.

    راش: Brish

    نام علمی این چوب Faguskhl نام فارسی و بومی راش و مرس و نام انگلیسی آن Beech است.از خواص ظاهری چوب راش درون نامشخص و به رنگ کرم مایل به قرمز است.دوایر سالیانه فشرده و در نتیجه در مقاطع طولی دارای خطوط کم و بیش مشخص ناشی از آن است. از بارزترین خصوصیات آن شاید بتوان به پره های چوبی در مقاطع طولی اشاره کرده که در مقاطع شعاعی به پرمگسو در مقاطع مماسی به دوک معروفند و این پره ها به صورت لکه های قرمز دیده می شوند چه بساگاهی این پرمگس های زیبا عیب محسوب می شوند چرا که به عقیده نجاران این بخشهای چوب پس از رنگ کاری سیاه می شوند.

    گونه راش چوبی نیمه سنگین و دارای بافتی همگن است. و تقریبا” مقاوم در برابر حشرات و قارچهاست.گرد بینه های درجه۱ و ۲راش در ایران بیشتر به مصرف کارخانجات روکش و تخته لایه می .بنا به اطاعات بازار به دلیل بافت همگن و درجه سختی مناسب این چوب بیشترین تقاضا را برای خرید به منظور تهیه مبل در بازار دارد.

    همچنین به دلیل قابلیت آغشتگی با انواع محلولهای حفاظتی بیشترین گونه مصرفی در کارخانه های اشباع است.البته اخیرا” گونه های خارجی راش از طریق آذربایجان وارد ایران شده است که بنا به اعدای مبل سازان و فروشندگان چوب کیفیت چوب راش ایرانی را ندارد ولی به دلیل ابعاد و رطوبت مناسب تخته ها میزان ضایعات کمتری در امر فرآیند تولید دارد.

    افرا: maple

    این خانواده دارای گونه های مختلفی در ایران است از جمله می توان افرا پلت،افرا شیردار وکیکم را نام برد. بزرگترین و فراوانترین افرای ایران اپلت با نام علمی insigne bosso و نام انگلیسی maple hs است.این گونه چوب درون نامشخص، چوب سفید مایل به کرم با درخشندگی کم و بیش صدفی دارد. دوایر سالیانه به دلیل فشردگی چوب تابستان در مقطع عرضی کاملا”مشخص و مقطع مماسی نقوش مواج و در مقطع عرضی نقوش رگه ای مانند ایجاد کردهاست که پره های چوبی ظریف و قهوه ایرنگ و براق در دو مقطع مختلف طولی به صورت طولی به صورت لکه ها و دوک ها نمایان است.

    چوبی نیمه سنگین با پرداخت آسان و هم کشیدگی کم باعث شده تا در صنعت مبلمان و روکش گیری جایگاهویژه ای داشته باشد.

    چوب روسی:

    واژه چوب روسی در بازار چوب ایران به هر نوع چوب سفید رنگ وارداتی از روسیه تلقی می شود و کاربرد آن هم چنان تفاوتی نمی کند در حالیکه این چوبه سفید خودشامل گونه های کاملا” متفاوت چون نراد،نوئل و انواع کاجها می شوند.

    همچنانکه گفته شد یکی از گونه های چوبی که به چوب روسی معروف استabies یا نراد است که نام رایج آن در دنیا fir و aspen است.این چوب فاقد درون چوب مشخص و به رنگ سفید مایل به قرمز،فاقد مجاری سمغی ،راست تار ،سبک ،واکشیدگی و هم کشیدگی کم ،قابلیت ترک خوردن کم هنگام خشک شدن ،بسیار خوش کار ، سمباده خوری خوب، میخ خوری و پیچ خوری عالی هستند ولی با وجود تمام مزایا به راحتی در مقابل قارج ها درچار مرض لکه آبی یا لکه قرمز می شود و از استحکام آن می کاهد.حشرات نیز علاقه زیادی به لانه گزینی و تخم گذاری در آن دارد و باید توجه داشت که چوبها دارای رگهقرمز به هنگام خشک شدن کاما” تاب برمی دارد.

    این چوب به علت سبکی و ضریب الاستیته از بهترین چوب ها برای اسکلت ساختمان هاست . الیاف بلند وخمیر سفید آن در کاغذ سازی مصرف فراوان دارد. در ایران این چوب غالبا” در صنایع مبلمان استفاده می شوند.

    ماهاگونی یا آکاژو:

    آکاژو ها به دو دسته آکاژویی آمریکایی و افریقایی تقسیم می شود که اغلب آکاژویی افریقاییی دربازار ایران یافت میشود. نام علمی این گونه khaya inveeuonsis و از خانواد miliacea است. نام های محلی متفاوتی در کشور های مختلف آفریقا دارد .درون چوب قرمز رنگ و برون چوب نازک سفید مایل به صورتی رنگ دارد.بافت یکدست و وجود پرمگسهای درخشان و براق که با تغیر جهت نوردرخشش متفاوتی دارند از ویژگی های شاخص این چوب است.در مقطع شعا عی نقوش نواری صذفی و در مقاطع مماسی نقوشی متنوع چونموجی مجعد جناغی دارد.که یکی از پر مصرف ترین چوبهای دنیا برای تهیه روکش های قیمتی است.به دلیل هم کشیدگی و واکشیدگی کم در هنگام خشک شدن کمتر دچار عیب می شود.ضربه پزیری خوب،پرداخت عالی ،پیچخوری و میخ خوری بالا ازخوصصیات بارز این چوب است ولیرنگ پزیری و واکس خوری باید همراه با بتونه کاری انجام شود.در تهیه روکش و مبل سازی بیشترین مصرف را داراست.

    به دلیل ضربه پذیری و ضرریبه الاستیسیته بالا در تهیه قایقهای بادبانی و تفرحی مناسب است. لازم به ذکر است که چوب های دیگری نیز تحت عنوان آکاژو در بازار دیده می شوند که اسامی واقعی انها سیپو ،کیسپو و ساپلی است.

    مشخصات: ,

    + نوشته شده در  یکشنبه هشتم آذر 1388ساعت 16:8  توسط abdolla zamani  |