The transmitted waves are probably affected by micro- and macrostructures [14]. The microstructure can be regarded as homogeneous because wood cells, such as the tracheids, fibers, and ray cells, have cross-sectional dimensions much smaller than the wavelength of the MMWs, 1–10 mm. The macrostructure such as **annual** **rings** can be regarded as inhomogeneous because **annual** ring widths are close to or longer than the wavelength. Part of this report was presented at the 61st **Annual** Meeting of the

The second potential environmental stimulus for ring formation is insolation, which is known to have an important influence on tropical tree phenology (Borchert et al. 2005, 2015). For example, some species have been observed flushing their leaves twice a year at the Equator in response to two insolation peaks per year, and only once a year farther from the Equator where insolation has just one peak per year (Borchert et al. 2015; Calle et al. 2010). Daily insolation data are shown in Fig. 1 (green lines). The Suriname site is closest to the ‘insolation equator’ which, at *3°N, is the latitude where insolation has the lowest year-round variation (Borchert et al. 2015). Across the other study sites, where Cedrela is known to exchange its leaves once per year and form **annual** **rings**, there is no clear relationship between insolation seasonality and Cedrela growth rhythm. Of these seven sites, some have two peaks of insolation per year (Ecuador, Venezuela and Manaus), and some just one peak of insolation per year (Bolivia, Aripuana˜, Nova Iguac¸u and Campeche; Fig. 1). Therefore, we believe that solar insola- tion is not the primary driver of the distinct biannual ring formation of Cedrela in Suriname. Furthermore, periods of leaf-fall do not consistently coincide with increasing, decreasing, peak or minimum insolation, though leaf-flush occurs more commonly when insolation is increasing or nearing its **annual** maximum (Fig. 1).

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Wood (xylem) is created by the dividing activity of the cambium secondary meristem (HOADLEY 1990). During every growing period, trees growing in the temperate region create a new diameter (radial) increment of wood – an **annual** ring (WAGENFÜHR 1999). The activity of cambium is aﬀected by a number of external and internal factors. Climatic conditions and biotic agents are ranked among outer factors. Internal factors are genetically conditioned factors and the health condition of a tree. The an- nual ring width is unique for a certain time and place where a given tree grows (KLEIN 1998). Trees grow- ing in the same region and thus in the same climatic conditions show the same response expressed by the **annual** ring width. Thus, there is similarity in the change of the **annual** ring width within a stand particularly as for maximum and minimum values (DOUGLASS 1937). On the basis of these ﬁndings, it is possible to assign the year of origin to particular **annual** **rings** and to carry out the dating of other samples of wood according to the similarity of the sequence of **annual** **rings** of variable width. These problems are dealt with by a scientiﬁc discipline

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We suggest with this paper that the ligni ﬁ cation of EW cells during **annual** growth ring development might indicate a cavitation-avoidance response by reducing the size of lumens in order to maintain the in- tegrity of the water column between the roots and the stomata. We have initiated research that aims to corroborate the results presented here, by direct measurements of cell wall thickness and lumen diameters from these same cores. It is clear from our study that BI relates to seasonal climate variability, and the response of EWBI in particular shows a very strong and coherent expression of ENSO-related varia- bility across much of the planet (Fig. 11). Our database of cypress re- cords extends from southern to northern Vietnam, and we are ex- panding into Laos on the western side of the Annamite Range. By combining RW and BI parameters there is great potential to produce the most highly robust tree-ring reconstructions of climate yet seen from the global tropics. We will continue to research the mechanisms of xylem genesis within the context of the ecophysiology of the species, and this should allow for mechanistic climate-growth models that are more accurate than the traditional empirically derived reconstructions.

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Regarding the abrasive wear property of Douglas fir, in specimens with the same dimensions but different annual ring widths, the dispersion of the wear coefficient in[r]

We found that all sample trees showed the same variation trend in the radial direction (Figs. 1, 2), so we compared the variations of the lumber and small clear specimens using[r]

algorithm acted to the moment of stabilisation, i.e. the moment when changes no longer occur in the obtained clusters. In the performed calculations a solution was found each time after the first itera- tion. Cluster centres were selected in such a way so as to maximise the cluster distance. Examples were ascribed to clusters due to their distance from the centres. At such assumptions the algorithm iden- tified the number of observations (**annual** **rings**) to the cluster of juvenile wood and mature wood. Calculations with the use of the algorithm were not applied to discs coming from higher sections of stems if the number of **rings** at those cross-sections was smaller than or equal to the number of **rings** of juvenile wood, calculated by the algorithm on a disc from a lower section. In such a case it was as- sumed that a given stem cross-section is composed entirely of juvenile wood. Such a method of iden- tification of the boundary between juvenile and mature wood was used for each tree and each disc except for the situation described above. Addition- ally, a graph was also used, illustrating changes in the share of late wood on the ray. After a number of **rings** ascribable to each of the wood zones was ob- tained, their width was summed up to calculate the width of the cylinder of juvenile wood (mm) and the width of the ring of mature wood (mm). The sum of the above-mentioned widths constitutes the width of a given disc inside bark. Results were used to calculate volumes of juvenile and mature wood in tree stems.

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Species types, stand density, and number of annual rings in trees growing after abandonment of substitution forest for half a century.. 1 Species types and stand density NT and BA.[r]

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The internal structure of different types of graphite commonly found in the ductile cast iron were investigated by TEM technique for TEM samples prepared by FIB method to understand their nucleation and growth. Spheroidal and vermicular graphite were observed in the ductile cast iron with spheroidizing treatment. Flake graphite was observed in the same cast iron without the spheroidizing treatment. The spheroidal graphite had a three-fold internal structure, with an amorphous-like central region, **annual** **rings** of a layered intermediate region, and an outer region made up of large polygonal crystalline platelets in a mosaic-like structure. The vermicular and ﬂ ake graphite had a similar to that of the outer region of the spheroidal graphite, in that it consisted of similar crystalline platelets. [doi:10.2320 / matertrans.M2014167]

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After measuring the dynamic Young’s modulus, the logs were cut at approximately 120 and 370 cm from the butt end (Fig. 1). They were then lumbered into 250-cm long and 6-cm wide boards that included the pith; these boards were then kiln dried. They were then conditioned at 20 °C and 65 % RH for more than 1 month after being kiln dried. Then, they were cut at 40–210 cm from the butt end and lumbered into boards with lengths and widths of approximately 170 and 2 cm, respectively, as shown in the figure. The number and the width of the **annual** **rings** were measured on the transverse face of the butt end of the boards. Ten sets of wood specimens (20 (T) 9 20 (R) 9 60 (L) mm) that were continuous in the radial direction were prepared from each board. These specimens were further conditioned at 20 °C at 65 % RH Table 1 Properties of logs

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scanning microscopy (CLSM) and soft cavities for the same area of the tracheid of earlywood tracheids from two annual rings. Earlywood tracheids from compression wood genera[r]

Due to the orthotropic nature of wood, mode I fracture toughness for different directions of crack propagation is expressed using the six principal crack-propagation systems. End checks occur perpendicular to the tangential direction and propagate along radial, longitudinal, and intermediate directions simultaneously, corresponding to TR, TL, and intermediate systems, respectively. Thus, it is important to evaluate fracture toughness not only for TR and TL cracks, but also for intermediate cracks. Nevertheless, no measure of the fracture toughness of intermediate cracks has been reported. This study was aimed at understanding the pattern of end-check occurrence and propagation at the scale of **annual** **rings** and at examining the mode I fracture toughness of sugi in TR, TL, and intermediate systems, which corre- spond to the direction of end-check propagation. The crack propagation for various directions from TR to TL systems was evaluated based on the obtained fracture toughness values and load–crack opening displacement (COD) curves.

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ANALYSIS OF THE RADIAL GROWTH TREND OF TREES OF THE YOUNGER AND OLDER GENERATIONS OF INVESTIGATED SPECIES Fir The width of annual rings of fir trees of the younger generation was fitted [r]

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To our knowledge, there has been no quantitative evaluation of the depths of **annual** **rings**. Previous research [11, 12, 13, 14] showed that eccentric growth occurs but no detailed evaluation of individual **rings** has been done. The purpose of this study is to use computer programs to create an accurate pictorial representation of three xylary **rings** in several stem segments in order to visualize **rings** among segments. Thus, images of three xylary **rings** were individually isolated and visualized from all other materials in the images. A three-dimensional visualization of the three xylary **rings** for the four segments was constructed to show a combined view of ring eccentricities along a stem.

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It is probable that the number of fires recorded in the **annual** growth **rings** of coast redwood trees is a subset of those fires that burned in adjacent grasslands and oak savannahs. The Ohlone Indians burned primarily to enhance the growth and productivity of perennial grasses used for food and the majority of this burning was done in the fall (Chuck Striplen, personal communication, 2004). Fires also provided browse for high-value game species, restricted detrimental communities under high-value oak stands, and were used to enhance and create specific botanical products for baskets, cordage, clothing, tools, nets, and traps.

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Various generalizations of symmetric **rings** have been done by many authors over the last several years. R is weak symmetric ([5]) if for any a, b, c ∈ R, abc ∈ N (R) implies acb ∈ N (R). R is central symmetric ([4]) if for any a, b, c ∈ R, abc = 0 implies bac ∈ Z(R). R is generalized weakly symmetric (GWS) ([11]) if for any a, b, c ∈ R, abc = 0 implies bac ∈ N (R). It follows that the class of GWS **rings** contains the class of weak symmetric **rings**. Again, it is known that central symmetric **rings** are GWS ([11]).

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2. A decomposition theorem for **rings**. In this section, we establish a decompo- sition theorem which in turn allows us to study the commutativity of such **rings**. Throughout this section, R represents an associative ring (may be without unity 1), and C = N(R), the set of nilpotent elements of R. A ring R is called periodic if for each x ∈ R, there exist distinct positive integers m = m(x), n = n(x) such that x m = x n .

In Chapter 3 we begin the proof of our main theorem. We adapt the proof of a theorem by S. Brenner [10], which shows that the 2 x 2 upper triangular matrix ring T2( Z /p 4Z ) is of infinite type, to the more general case of T2(.D/(inD ), where D is a non-commutative local Dedekind prime PI ring and dD its maximal ideal. This result is crucial for the proof of Theorem 5.1.12. The reduction o f our problem to this case is allowed by a theorem of M. Ausländer (cf. Theorem 3.2.1) on trivial extension **rings** o f Artin algebras. We describe this theorem and show that it holds also for Artinian PI **rings**. Then we analyze the graph of links between maximal ideals of R. W e show that if R is a prime ring satisfying the hypothesis of Theorem 5.1.12 then all cliques of maximal ideals of R are finite. In the last section of this chapter we look at connections between Artinian serial **rings** and **rings** of finite representation type. We show that if R is a semiperfect local Noetherian PI ring which is not Artinian and such that R /J ( R )2 is of finite representation type, then R is a hereditary prime ring. Finally, we introduce some **rings** related to the ring R satisfying the hypothesis of Theorem 5.1.12, which inherit the property of the homomorphic images and that we shall use for the proof of the theorem.

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Recall that an endomorphism α of a ring R is called rigid (see [5] and [12]) if aα(a) = 0 implies a = 0 for a ∈ R. R is called an α-rigid ring [12] if there exists a rigid endomor- phism α of R. Note that any rigid endomorphism of a ring is a monomorphism, and α-rigid **rings** are reduced by [12, Propositions 5 and 6].

In ring theory, the notion of annihilator is an important tool for studying the structures. Many characterizations and structure theorems can be derived by using this notion. On the other hand, certain classes of **rings** (e.g., Baer **rings** and Rickart **rings**) are defined by considering annihilators ideals. In the present work, we introduce a class of **rings** which is close to the class of Rickart **rings**. We then investigate endomorphism **rings** having this property. This will enable us to obtain characterizations of certain classes of **rings**, namely the SV-**rings** and the hereditary **rings**.

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