Post-growth Period Research Articles

Formation features of N3V centers in diamonds from the Kholomolokh placer in the Northeast Siberian Craton

In recent years, despite significant progress in the development of new methods for the synthesis of diamond crystals and in their post-growth treatment, many questions remain unclear about the conditions for the formation and degradation of aggregate impurity nitrogen forms. Meanwhile, they are very important for understanding (evaluating) the origin, age, and post-growth conditions of natural diamonds. In the present work, an attempt was made to analyze the causes of the formation of high concentrations of N3V centers in natural IaB-type diamonds from the Kholomolokh placer (the Northeast Siberian craton). The possibility of decay of B centers during the plastic deformation of diamonds is analyzed and experiments on the high-temperature annealing of diamonds containing B centers are reported. The formation of N3V centers during the destruction of the B centers at high-pressure annealing of crystals has been established by experiment. It is assumed that, in the post-growth period, diamond crystals were exposed to tectono-thermal stages of raising the superplumes of the Earth's crust of the Siberian craton.

Energy exchange between the atmosphere and a subalpine meadow in the Qilian Mountains, northwest China

Understanding energy exchange between the atmosphere and the Earth’s surface is crucial. We observed the patterns of energy exchange between the atmosphere and a subalpine meadow in the Qilian Mountains, northwest China over the period of 2014 to 2016. Annual variations in energy exchange in study area exhibited drastic differences during time periods of frozen soil and non-frozen soil. Specifically, more than 80% and 28% of net radiation (Rn) were converted to sensible heat (H) during the frozen and non-frozen soil periods, respectively, whereas approximately 17% and 35% of Rn were converted to latent heat (LE) during the frozen and non-frozen soil periods, respectively. The non-frozen soil period was divided into the pre-growth period, the growth period, and the post-growth period. The high Bowe ratio (β) values of the pre-growth period were 4.34, 3.60, and 8.39 in 2014, 2015 and 2016, respectively. In general, rapid increases in Rn during this period increased the values of H, LE, and soil heat flux (G). The growth period was defined by a low β value that fluctuated between 0.3 and 0.4. The average β values for the post-growth period during 2014, 2015, and 2016 were 1.49, 3.12, and 2.37, respectively. The high decoupling coefficient (Ω) for the growth period indicated that the contribution of Rn to LE was greater than that of vapor pressure deficit (VPD). The small value of Ω during the other periods indicated that the effect of VPD on LE dominated that of other factors. The seasonal patterns of energy exchange showed that vegetation phenology is the major factor that affects energy partitioning significantly in the alpine meadow ecosystem in the Qilian Mountains. The annual energy partitioning in the same ecosystem over 3 years was not constant, and climate may be the main factor that influences interannual variations in energy exchange.

The characteristic photoluminescence and EPR features of superdeep diamonds (São-Luis, Brazil)

Photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR) were used for the first time to characterize properties of superdeep diamonds from the Sao-Luis alluvial deposits (Brazil). The infrared measurements showed the low nitrogen content (>50 of 87 diamonds from this locality were nitrogen free and belonged to type IIa) and simultaneously the extremely high level of nitrogen aggregation (pure type IaB being predominant), which indicates that diamonds under study might have formed under high pressure and temperature conditions. In most cases, PL features excited at various wavelengths (313, 473, and 532 nm) were indicative of different growth and post-growth processes during which PL centers could be formed via interaction between vacancies and nitrogen atoms. The overall presence of the 490.7 nm, H3, and H4 centers in the luminescence spectra attests to strong plastic deformations in these diamonds. The neutral vacancy known as the GR1 center has probably occurred in a number of crystals due to radiation damage in the post-growth period. The 558.5 nm PL center is found to be one of the most common defects in type IIa samples which is accompanied by the EPR center with g-factor of 2.00285. The 536 and 576 nm vibronic systems totally dominated the PL spectra of superdeep diamonds, while none of “normal” diamonds from the Mir pipe (Yakutia) with similar nitrogen characteristics showed the latter three PL centers.

Pathways toward Photoinduced Alignment Switching in Liquid Crystalline Block Copolymer Films

The pathways toward linearly polarized light (LPL)-induced alignment switching in a diblock copolymer film composed of liquid crystalline (LC) azobenzene (Az) and amorphous poly(butyl methacrylate) (PBMA) blocks were studied in detail using polarized UV–vis absorption spectroscopy, grazing incidence small-angle X-ray scattering measurements, and polarized optical microscopy and transmission electron microscopy observations. The hierarchical structures of microphase-separated cylinders of PBMA in a smectic LC Az layer matrix were prealigned by LPL and then irradiated by orthogonal LPL, which resulted in alignment switching to the orthogonal direction. In this process, the large prealigned domains were divided into substantially smaller domains at the submicrometer level, and then the structures were realigned in the orthogonal direction in a strongly cooperative manner, most likely through the domain rotation mechanism. The alignment change consisted of three stages: (i) fluctuations in the smectic layer of LC Az side chains in the initial state and breaking up of smaller grains to the submicrometer level before the orientation change (induction period), (ii) actual rotation of the divided domains driven by the photoinduced reorientation of Az mesogens (action period), and (iii) slower fusion and growth of smaller domains in the orthogonally realigned direction (postgrowth period). New aspects of dynamic self-assembly behavior in which different hierarchical structures are involved are proposed.

Neonatal Exposure to Sevoflurane Causes Significant Suppression of Hippocampal Long-Term Potentiation in Postgrowth Rats

The inhaled anesthetic sevoflurane is commonly used for neonates in the clinical setting. Recent studies have indicated that exposure of neonatal rodents to sevoflurane causes acute widespread neurodegeneration and long-lasting neurocognitive dysfunction. Although acute toxic effects of sevoflurane on cellular viability in the hippocampus have been reported in some studies, little is known about the effects of neonatal sevoflurane exposure on long-term hippocampal synaptic plasticity, which has been implicated in the processes of learning and memory formation. Our study is the first to examine the long-term electrophysiological impact of neonatal exposure to a clinically relevant concentration of sevoflurane. On postnatal day 7, rats were exposed to sevoflurane (1% or 2% for 2 hours) with oxygen. To eliminate the influence of blood gas abnormalities caused by sevoflurane-induced respiratory suppression, a group of rats were exposed to a high concentration of carbon dioxide (8% for 2 hours) to duplicate respiratory disturbances caused by 2% sevoflurane exposure. Exposure of neonatal rats to 2% sevoflurane for 2 hours caused significant suppression of long-term potentiation (LTP) induction in the postgrowth period. There was no significant difference between the control group and the CO2-exposed group in LTP induction, indicating that sevoflurane-induced LTP suppression was not caused by blood gas abnormalities. Our present findings indicate that neonatal exposure to sevoflurane at a higher concentration can cause alterations in the hippocampal synaptic plasticity that persists into adulthood.

Application of synchrotron radiation to the study of the internal structure of natural regular and irregular diamonds

The internal structure of regular and irregular diamond crystals of the Snap Lake deposit of the Slave province (Canada) is studied using the Laue-SR synchrotron method. The crystals under study were classified into regular and irregular diamonds according to IR spectroscopy data. It is shown that irregular diamonds, in contrast to regular, underwent plastic deformation during the postgrowth period. Plastic deformation by slip or spinel-law twinning is observed for diamonds with insignificant nitrogen concentrations. For most studied crystals with high concentrations of platelets (B’ defects), irregular misorientations of local regions of a deformed crystal, such as faults and kinks, are characteristic. The interaction of dislocations formed during plastic deformation, with the dislocations surrounding the platelets, causes destruction of the latter at high P-T parameters typical of the upper mantle.

The surgical and orthodontic management of cherubism in a growing child

Cherubism is a rare non-neoplastic disease that affects the jaws causing significant destruction and disfigurement. The disease also affects the normal eruption, occlusion and function of the dento-alveolar complex. Cherubism may radiographically and histologically resemble central giant cell granuloma, fibrous dysplasia and other giant cell lesions. The case of a 15-year 4-month-old girl with no obvious facial swelling or signs of cherubism is described in this report. The patient presented with a dental malocclusion that included the ectopic eruption and displacement of teeth caused by the lesion. The radiographic findings derived from Cone Beam Computed Tomography (CBCT) technology are described. This case report details the orthodontic and surgical diagnosis and management of a teenager during the post growth period.

Strategies to Accelerate Industrialization of FIJI

The terms of trade that Fiji faces in the post-growth period will deteriorate as the international price of her exports (i.e., agricultural products) tends to increase less rapidly compared with that of her imports (i.e., manufacturing products). This deterioration of the terms of trade facing the Fijian exporters could offset the normal gains associated with growth over time. Therefore Fiji should accelerate industrialization immediately as her national goal. In order for Fiji to successfully accelerate industrialization, the government should establish a set of basic principles as follows: (a) condensed growth, (b) light manufacturing industrialization first, heavy and chemical industrialization later, (c) government initiatives, (d) foreign capital inducement and export-led growth, and (e) growth primacy. Based on the above principles of Fiji's industrialization, the following development strategies should be adopted: (a) Leadership commitment for industrialization, (b) Government-led development strategy, (c) Outward-looking development strategy, (d) Growth-first-distribution-later policy, (e) Domestic resources mobilization and foreign capital inducement, (J) Human resource development, (g) Environmentally sustainable development To fully moderni=e Fiji on her track of industrialization, the following development strategies should be adopted: (a) Village movement, (b) Promoting economic and social status of indigenous Fijians, and (c) Nation building

Energy exchange between the atmosphere and a meadow ecosystem on the Qinghai–Tibetan Plateau

To reveal the potential contribution of grassland ecosystems to climate change, we examined the energy exchange over an alpine Kobresia meadow on the northeastern Qinghai–Tibetan Plateau. The annual pattern of energy exchange showed a clear distinction between periods of frozen soil with the daily mean soil temperature at 5 cm ( T s5 ≤ 0 °C) and non-frozen soil ( T s5 >0 °C). More than 80% of net radiation was converted to sensible heat ( H) during the frozen soil period, but H varied considerably with the change in vegetation during the non-frozen soil period. Three different sub-periods were further distinguished for the later period: (1) the pre-growth period with Bowen ratio ( β) > 1 was characterized by a high β of 3.0 in average and the rapid increase of net radiation associated with the increases of H, latent heat (LE) and soil heat; (2) during the growth period when β ≤ 1, the LE was high but H fluxes was low with β changing between 0.3 and 0.4; (3) the post-growth period with average β of 3.6 when H increased again and reached a second maximum around early October. The seasonal pattern suggests that the phenology of the vegetation and the soil water content were the major factors affecting the energy partitioning in the alpine meadow ecosystem.