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A complete ASE analysis in a 3-level laser system based on the model of the geometrically dependent gain coefficient (GDGC) is presented. For the study, the photon density/intensity rate equation in the saturated and unsaturated conditions, along with reported experimental measurements on the ASE output energy and spectral bandwidth for N2-lasers were utilized. It was found that the GDGC model is able to explain the ASE output energy behavior and gain profiles correctly. In addition, the model was used to predict the spontaneous emission bandwidth Δν 0 and consequently the stimulated emission cross-section for the C→B transition of nitrogen molecule at 337.1nm. In this work, for example, Δν 0 was found to be 766GHz (2.9Å) which is consistent with the earliest experimental observation on the ASE bandwidth reduction in a N2-laser as reported to be ~3. This is the first theoretical result that explains the spontaneous emission bandwidth which is different from the commonly used value of ~1Å obtained from measurements of N2-lasers output spectra. The method was also applied for a filament N2 laser for the C→B transition produced in atmosphere, and a good consistency between the laboratory and filament lasers was obtained. Details of the calculations for this study are presented. The results obtained from 3-level systems confirm further the potential of applying the GDGC model for the ASE study in different laser systems and is unifying lasers of the same active medium. [ABSTRACT FROM AUTHOR]

Based on the reported experimental measurements on the output power in a transversely excited nitrogen laser with a weak corona preionization and rate equations, a simulation study was made to describe the laser output power behavior. For the study, we first made a literature survey for the appropriate E/p functional dependences of nitrogen molecules on drift velocity vd, and the Townsend ionization coefficient α, to be applied for the laser operational characteristics of high gas pressures up to 1 atmosphere, and 20 < E/p < 1000 V cm−1 Torr−1. For the study when the corona UV preionization is applied, it was realized that it is necessary to modify the Townsend ionization coefficient to include the effect of the preionization for the laser system. This realization revealed that the Townsend coefficient upon utilizing the corona effect, (α/p)corona, can be viewed as a perturbation to be added to the (α/p)main due to the main gas discharge, where the total (α/p)t = (α/p)main + (α/p)corona was used for the calculation. We also introduced a single α/p relation with A* and B* coefficients to explain the gas discharge due to both the main and corona discharges. The results of the two approaches are introduced and have been compared with each other. The present study indicates that laser optical measurements, by themselves, constitute a reliable approach for understanding the physical quantities that are involved during plasma formation in a gas discharge. Details of the approach will be presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract: By applying the geometrical model of the gain coefficient and population, we managed to describe the amplified spontaneous emission (ASE) in a N 2-laser. For this purpose, and also for verifying the geometrical modeling we used the earliest available experimental data for the N 2-laser output energy ε ASE versus the laser excitation length reported by Leonard for a N 2-laser operating at low gas pressure (20Torr), with no preionization. The ASE output energy calculation was performed both numerically and analytically. Upon applying the full description of the gain coefficient and upper state population (with b-parameters≠0), the numerical calculations found to explain the experimental measurements of the ε ASE versus excitation length correctly. For the analytical approach, we used the approximate expression for the gain and population (with b-parameters=0) for simplifying the calculation. The results corresponding to both cases are introduced. Furthermore, the calculated gain coefficient for describing the Leonard''s experiment has been compared with our recent gain measurements in a N 2-laser with corona preionization, and higher operational gas pressure (∼100Torr). This observation is indicating that while the gain coefficients in both experiments are obeying the generalized formulation of the gain coefficient, but the gain profile for the higher gas pressure is slightly higher than the case when the laser is operating at a low gas pressure. That is, the laser geometry still has the dominant contribution for the laser gain coefficient. [Copyright &y& Elsevier]

Abstract: Based on our previously reported measurements on the gain-value in a N2- laser and numerical calculations, we introduce a method to obtain an analytical expression for the small signal gain, g 0, where the dependency of g 0 on the laser geometrical configuration, including electrodes length and gap separation, is demonstrated. For this study one- and two-dimensional approaches for the photon density have been applied independently to determine gain-parameter, where for explaining the observed dependency of the gain-parameter on the laser electrodes separation, d AMP, which was found experimentally and explained by an empirical expression of the type g 0 = r + q/d AMP, with r and q some constants, realization of introducing an extra dimension along the gap separation was unavoidable. For the electrodes length, l AMP, we have already shown that an empirical equation of the type g 0 = m + n/l AMP, with m and n some constants, is consistent with the measurements corresponding to N2-lasers. With this realization, it is proved that the gain-parameter in N2-lasers can be written as g 0 abovethreshold = m″+ g 0z (γ L z , z)+ g 0y (γ L y , y), where it consists of two independent gain-values along the electrodes length (z) and gap separation (y) with the corresponding power losses given by γ L z and γ L y . m″ is a very small quantity showing that laser is operating slightly above the threshold. The results of this calculation are consistent with our recent measurements and also other reported N2-laser gain values measured under moderate current density conditions. To check the validity of the model for other types of lasers, the reported gain-values for copper vapor lasers of different laser tube radii, R AMP, and tube lengths, l AMP, have been examined using the one-dimensional model of either g 0(R AMP) or g 0(l AMP) and the consistency with the observed measurements was found to be quite satisfactory. The model was also found to be valid for the excimer lasers of different types, different gas mixtures and pressures at a constant input operational voltage. Due to limited numbers of the reported experimental measurements, for the graphs preparation of g 0(l AMP) in excimer lasers we used the observed data at V 0 =30kV and also some variations of the input voltages in the range of ΔV ≅20kV have been adopted. The results for both cases were found to be consistent with the proposed one-dimensional model. [Copyright &y& Elsevier]

As one of the main origin centers of nut trees, Iran is the fourth leading nut crops producer in the world (6% of total nut production). Due to the high genetic diversity, development of new varieties and rootstocks with desirable characteristics have been highly considered by fruit breeders in Iran. In this regard, molecular breeders concentrate on filling the gaps in the conventional breeding with the aim of accelerating breeding programs. Recent advancements in molecular breeding such as next-generation sequencing (NGS) techniques, high-throughput genotyping platforms and genomics-based approaches including genome wide association studies (GWAS), and genomic selection (GS) have opened up new avenues to enhance the efficiency of nut trees breeding. Over the past decades, Iranian nut crops breeders have successfully used advanced molecular and genomic tools such as molecular markers, genetic transformations and high-throughput genotyping to explore the genetic basis of the desired traits and eventually to develop new varieties and rootstocks. Due to a broad international cooperation, a clear perspective is envisaged for the nut breeding programs in Iran, especially based on new biotechnology techniques. The propagation of nut trees in Iran have also been dramatically improved. Different types of grafting and tissue culture (micropropagation or somatic embryogenesis) techniques for propagation of nut crops have been studied intensively in the last 30 years in Iran and the successful techniques have been commercialized. Several certified nurseries are producing grafted and micropropagation plants of walnut, pistachio and other nut crops commercially. A part of the grafted and micropropagaited plants of nut crops in Iran is being exported to the other countries. Establishing modern orchards of nut crops using new cultivars and rootsocks is presently being advised by professional consultants.

Generation of high-order harmonics (HOHs) and attosecond pulses in the barrier suppression ionization regime for a target of hydrogen molecular ion, H2+, with large inter nuclear distance is introduced in this work. Some broadband femtosecon laser pulses are designed based on multicolor beam superposition method in order to interact with H2+. Behavioral study of harmonics cutoff, attosecond pulse widths and intensities, along with the maximum ionization intensity with respect to the spectral width of driving pulses was carried out. Molecular orbitals in this study are estimated via the linear combination of atomic orbital approximation, and temporal variations of these orbitals are studied in the various ionization regimes. It is seen in this work that although the cutoff harmonic is increased by the driving pulse intensity, but it is insensitive to the spectral driving pulsewidth. This study showed that intensities of the generated attosecond pulses gradually decreased by increasing the bandwidth of the driving laser pulse, but the duration of them is shown to be insensitive in this respect. [ABSTRACT FROM AUTHOR]

While numerous studies explored the response of walnut plants to drought stress (DS), there remains a significant gap in the knowledge regarding the impact of heat stress (HS) and the combined effects of DS and HS on the recovery capacity of walnut trees. This study aimed to investigate the mechanism of Persian walnut (cv. Chandler) response to the combined DS and HS, focusing on various aspects including photosynthesis, water relations, and osmotic regulation. The treatments involved subjecting plants to DS (through a withholding method for 24 d), HS (gradually up to 40 °C for 8 d), and a combined DS and HS, which were compared to a control group (no stress) during the stress and recovery phases. The results showed that DS had significantly more negative effects on chlorophyll content, relative water content (RWC), leaf water potential (WP), osmotic potential (OP) compared to HS. Involvement of osmoregulation mechanism was detected more in DS and HS plants through the accumulation of proline, glycine Betaine and total soluble carbohydrates. The functionality of photosynthesis was significantly impacted by both HS and DS, respectively. While the HS accelerated the change of the abovementioned physiological processes in drought-stressed seedlings. Consistently, more pronounced damage was found in leaves under the combined stress, alongside the decrease RWC, chlorophyll content and fluorescence ratios. Based on the analysis of the linear mixed-effect model, the effects of combined stress and HS on photosynthesis parameters were detected in the early stages of stress compared to DS. Within a range of stresses, the abovementioned physiological processes of individual and combined-stressed plants recovered to levels comparable to those of the control. Our results also showed a substantial reduction in the expression of the photosynthetic genes (Fd, Cyt b6f, and PsbB) in Persian walnut saplings under abiotic stress conditions indicating significant damage to their photosynthetic apparatus. This study highlights that, under scenarios of aggravating drought occurring with heat, walnut seedlings could face a high risk of damage to physiological structures in relation to the synergistically increased hydraulic and thermal impairments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Light plays a crucial role in photosynthesis, which is an essential process for plantlets produced during in vitro tissue culture practices and ex vitro acclimatization. LED lights are an appropriate technology for in vitro lighting but their effect on propagation and photosynthesis under in vitro condition is not well understood. This study aimed to investigate the impact of different light spectra on growth, photosynthetic functionality, and stomatal characteristics of micropropagated shoots of Persian walnut (cv. Chandler). Tissue-cultured walnut nodal shoots were grown under different light qualities including white, blue, red, far-red, green, combination of red and blue (70:30), combination of red and far-red (70:30), and fluorescent light as the control. Results showed that the best growth and vegetative characteristics of in vitro explants of Persian walnut were achieved under combination of red and blue light. The biggest size of stomata was detected under white and blue lights. Red light stimulated stomatal closure, while stomatal opening was induced under blue and white lights. Although the red and far-red light spectra resulted in the formation of elongated explants with more lateral shoots and anthocyanin content, they significantly reduced the photosynthetic functionality. Highest soluble carbohydrate content and maximum quantum yield of photosystem II were detected in explants grown under blue and white light spectra. In conclusion, growing walnut explants under combination of red and blue lights leads to better growth, photosynthesis functionality, and the emergence of functional stomata in in vitro explants of Persian walnuts., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Saeedi, Vahdati, Sarikhani, Daylami, Davarzani, Gruda and Aliniaeifard.)

In this paper, the effect of the active fiber's core/cladding area ratio on the output parameters of 1018 nm fiber lasers has been investigated. In this regard, we conducted a comprehensive study of two fiber lasers that utilized 25/400 and 30/250 µm ytterbium-doped fibers (YDFs), both theoretically and experimentally. The optimum length of YDFs required for 40 dB of amplified spontaneous emission suppression was calculated. Theoretical studies also identified the YDF breaking zone for lengths greater than the optimum. The experimental results showed that selecting the proper dimensions and coiling diameter for the active fiber significantly increased the power and efficiency of the YDF laser. We obtained an output power of 943 W with a 75.5% slope efficiency for the co-pumped 30/250 µm YDFL which, to the best of our knowledge, is the highest reported value for the 1018 nm co-pumped fiber laser. An analysis of the experimental and theoretical results revealed that YDFs with a core/cladding area ratio greater than 1% are more suitable for realizing a high-power 1018 nm fiber laser. The findings of this study are crucial for the development of high-power 1018 nm fiber lasers with improved performance.

Persian walnut (Juglans regia) has a considerable economic importance worldwide. However, the vigor and vitality of walnut trees were heavily affected by bark canker during the last few years. Irregular longitudinal cankers in the outer bark, stem tissue necrosis, and bleeding with black-colored exudates walnut trees were observed in Kermanshah, Hamedan, Markazi, Alborz, Isfahan, Qom, Semnan, and Razavi Khorasan provinces in western, central and eastern Iran during 2018 and 2019. A total of 150 symptomatic samples were collected from affected walnut trees in order to identify bacteria associated with walnut decline. Two-hundred sixty strains with a metallic green sheen were isolated on EMB-agar medium. The pathogenicity of all strains was proved by inoculating a suspension of the bacterial strains under the bark of immature walnut fruits cv. 'Hartley'. Ninety-five strains caused necrosis and a dark-colored region in the mesocarp around the inoculation site 14 days post-inoculation. Moreover, 12 representative strains induced necrotic and black-colored tissues in the bark of young green twigs of two-year old walnut seedling cv. 'Chandler'. The strains were classified into four categories based on conventional phenotypic characters confirmed with the 16S rRNA gene sequences. A phylogenetic tree based on the concatenated sequences of two housekeeping gene fragments, gyrB and infB, indicated that strains including I1, Q6, and S6 were grouped in a cluster with Gibbsiella quercinecans FBR97 T as well as strains I2, I5, and KE6 were clustered with Rahnella victoriana FRB 225 T . Moreover, strains MR1, MR3, and MR5 were grouped with the Enterobacter hormaechei subsp. hoffmannii DSM 14563 T . The phylogenetic analyses based on the partial sequencing of housekeeping genes including fusA, pyrG, and leuS revealed that strains KH1, KH3, and KH7 belong to Citrobacter braakii species. To the best of our knowledge, this is the first report of C. braakii and E. hormaechei as plant pathogens and R. victoriana associated with walnut decline., (© 2023. The Author(s).)

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and their benefits to human health, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice used in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock-scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests.

Drought is an important environmental stress that has negative effects on plant growth leading to a reduction in yield. In this study, the positive role of nanoparticles of SiO 2 , Se, and Se/SiO 2 (SiO 2 -NPs, Se-NPs and Se/SiO 2 -NPs) has been investigated in modulating negative effects of drought on the growth and yield of strawberry plants. Spraying of solutions containing nanoparticles of SiO 2 , Se, and Se/SiO 2 (50 and 100 mg L -1 ) improved the growth and yield parameters of strawberry plants grown under normal and drought stress conditions (30, 60, and 100%FC). Plants treated with Se/SiO 2 (100 mg L -1 ) preserved more of their photosynthetic pigments compared with other treated plants and presented higher levels of key osmolytes such as carbohydrate and proline. This treatment also increased relative water content (RWC), membrane stability index (MSI) and water use efficiency (WUE). In addition, exogenous spraying of Se/SiO 2 increased drought tolerance through increasing the activity of antioxidant enzymes including catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) as well as decreasing lipid peroxidation and hydrogen peroxide (H 2 O 2 ) content. Increase in biochemical parameters of fruits such as anthocyanin, total phenolic compounds (TPC), vitamin C and antioxidant activity (DPPH) in strawberry plants treated with Se/SiO 2 under drought stress revealed the positive effects of these nanoparticles in improving fruit quality and nutritional value. In general, our results supported the positive effect of the application of selenium and silicon nanoparticles, especially the absolute role of Se/SiO 2 (100 mg L -1 ), on the management of harmful effects of soil drought stress not only in strawberry plants, but also in other agricultural crops.

Background: Flower development and sufficient fruit set are important parameters with respect to walnut yield. Knowledge about flowering genes of fruit trees can help to conduct better molecular breeding programs. Therefore, this study was carried out to investigate the expression pattern of some flowering genes (FT, SOC1, CAL, LFY and TFL1) in Persian walnut (cv. Chandler) during the growing season and winter dormancy., Results: The results showed that walnut flower induction and initiation in Shahmirzad, Iran occurred in early June and late September, respectively. After meeting chilling and heat requirement, flower differentiation and anthesis occurred in late-March and mid-April to early-May, respectively. Study of flowering gene expression showed that the expression of the FT gene increased in three stages including before breaking of bud dormancy, from late March to late April (coincided with flower differentiation and anthesis) and from late May to mid-June (coincided with flower induction). Like FT, the expression of SOC1 gene increased during flower induction and initiation (mid-May to early-August) as well as flower anthesis (mid-April to early-May). LFY and CAL genes as floral meristem identity genes are activated by FT and SOC1 genes. In contrast with flowering stimulus genes, TFL1 showed overexpression during winter dormancy which prevented flowering., Conclusion: The expression of FT gene activated downstream floral meristem identity genes including SOC1, CAL and LFY which consequently led to release bud dormancy as well as flower anthesis and induction. Also, TFL1 as a flowering inhibitor gene in walnut showed overexpression during the bud dormancy. Chilling accumulation reduced TFL1 gene expression and increased the expression of flowering genes which ultimately led to overcome dormancy.

Due to higher temperatures and lower water availability, climate change is likely to have a major impact on walnut production in the near future. Climate change will alter the land suitability for walnut cultivation around the world, especially in arid and semi-arid regions like Iran. Here, land suitability for the cultivation of walnut (Juglans regia L.) in Iran was determined using the GIS for present and future conditions (2020-2049) with an approach to climate change. Accordingly, data from 375 synoptic stations throughout Iran were gathered for climatic factors including average, minimum and maximum temperatures, relative humidity and chilling requirement. Also, ASTER sensors (Advanced Spaceborne Thermal Emission and Reflection Radiometer) and their data provided this research with cells that make a precision of 150 m (5 s), and the data were used for gauging geological parameters such as altitude and land slope. The electrical conductivity (EC) of soil and water were informed by the data bank of the Iranian Water Resources Management. The results of temperature simulations for the future (2020-2049) were analyzed by 21 AOGCM-AR5 models under the RCP4.5 emission scenario. In the first phase of evaluations, the maps of land suitability were constructed for present conditions by considering a network of the above-mentioned parameters. By combining these layers of information, the final map of land suitability was illustrated for walnut cultivation. In the second phase, the NEX-GDDP was used in order to determine land suitability for the future (2020-2049). The results showed that Iran currently has 582844 km2 of land suitable for walnut cultivation. However, the future will see less suitable lands: the current area will be reduced by 6.19%, from 582844 km2 to 546710 km2. In general, the northern, northwestern and western margins of Iran are currently suitable for walnut cultivation. By approximation, these lands will also be major areas for prospective cultivations of walnut in the future (2020-2049), even though their current stretch will be reduced., Competing Interests: The authors have declared that no competing interests exist.