Numerous Small Crystals Research Articles

A Targeted Multi-Crystalline Manganese Oxide as a Tumor-Selective Nano-Sized MRI Contrast Agent for Early and Accurate Diagnosis of Tumors.

Magnetic resonance imaging (MRI) is an important tool for the accurate diagnosis of malignant tumors in clinical settings. However, the lack of tumor-specific MRI contrast agents limits diagnostic accuracy. Herein, we developed αvintegrin receptor-targeting multi-crystalline manganese oxide (MCMO) as a novel MRI contrast agent for accurate diagnosis of tumors by coupling iRGD cyclopeptide PEGylation polymer onto the surface of MCMO (iRGD-pMCMO). The MCMO consisted of numerous small crystals and exhibited an oval structure of 200 nm in size. The iRGD-pMCMO actively recognizes tumor cells and effectively accumulates at the tumor site, consequently releasing abundant Mn2+ ions in a weakly acidic and high-GSH-expressing tumor microenvironment. Subsequently, Mn2+ ions interact with cellular GSH to form Mn-GSH chelates, enabling efficient T1-weighted MR contrast imaging. In vivo experiments indicated that iRGD-pMCMO significantly improved T1-weighted images, achieving an accurate diagnosis of subcutaneous and orthotopic tumors. The results verified that the T1 contrast effect of iRGD-pMCMO was closely associated with the expression of GSH in tumor cells. Altogether, the novel tumor-targeting, highly sensitive MRI contrast agent developed in this study can improve the accuracy of MRI for tumor diagnosis.

Microphysical processes producing high ice water contents (HIWCs) in tropical convective clouds during the HAIC-HIWC field campaign: dominant role of secondary ice production

Abstract. High ice water content (HIWC) regions in tropical deep convective clouds, composed of high concentrations of small ice crystals, were not reproduced by Weather Research and Forecasting (WRF) model simulations at 1 km horizontal grid spacing using four different bulk microphysics schemes (i.e., the WRF single‐moment 6‐class microphysics scheme (WSM6), the Morrison scheme and the Predicted Particle Properties (P3) scheme with one- and two-ice options) for conditions encountered during the High Altitude Ice Crystals (HAIC) and HIWC experiment. Instead, overestimates of radar reflectivity and underestimates of ice number concentrations were realized. To explore formation mechanisms for large numbers of small ice crystals in tropical convection, a series of quasi-idealized WRF simulations varying the model resolution, aerosol profile, and representation of secondary ice production (SIP) processes are conducted based on an observed radiosonde released at Cayenne during the HAIC-HIWC field campaign. The P3 two-ice category configuration, which has two “free” ice categories to represent all ice-phase hydrometeors, is used. Regardless of the horizontal grid spacing or aerosol profile used, without including SIP processes the model produces total ice number concentrations about 2 orders of magnitude less than observed at −10 ∘C and about an order of magnitude less than observed at −30 ∘C but slightly overestimates the total ice number concentrations at −45 ∘C. Three simulations including one of three SIP mechanisms separately (i.e., the Hallett–Mossop mechanism, fragmentation during ice–ice collisions, and shattering of freezing droplets) also do not replicate observed HIWCs, with the results of the simulation including shattering of freezing droplets most closely resembling the observations. The simulation including all three SIP processes produces HIWC regions at all temperature levels, remarkably consistent with the observations in terms of ice number concentrations and radar reflectivity, which is not replicated using the original P3 two-ice category configuration. This simulation shows that primary ice production plays a key role in generating HIWC regions at temperatures <-40 ∘C, shattering of freezing droplets dominates ice particle production in HIWC regions at temperatures between −15 and 0 ∘C during the early stage of convection, and fragmentation during ice–ice collisions dominates at temperatures between −15 and 0 ∘C during the later stage of convection and at temperatures between −40 and −20 ∘C over the whole convection period. This study confirms the dominant role of SIP processes in the formation of numerous small crystals in HIWC regions.

Sustainable polyamide elastomers from a bio-based dimer diamine for fabricating highly expanded and facilely recyclable microcellular foams via supercritical CO2 foaming

In this study, we developed a sustainable polyamide foam system. A new series of polyamide elastomers was synthesized using a bio-based dimer diamine monomer as a building block to copolymerize with aminocaproic acid and adipic acid through step-growth polymerization, followed by supercritical CO2 foaming for the fabrication of microcellular foams. The introduction of the branched-structured dimer diamine monomer effectively restricted the molecular packing and hydrogen bonding density of the polyamide system, leading to numerous small crystals acting as nucleation sites for heterogeneous cell nucleation. Simultaneously, the branched long chains of the dimer diamine formed chain entanglement networks, which increased the material melt strength against the elongational stresses of cell growth. The synergistic effect provided by dimer diamine led to the successful manufacture of foamed samples with a high expansion ratio and robust dimensional stability, effectively overcoming the foaming difficulties of high crystallinity and insufficient melt strength in traditional polyamide 6 (PA6). In addition, this polyamide elastomer foam system could be recycled and reprocessed due to the advantages of non-crosslinking and additive-free. Therefore, the study’s findings constitute a promising direction for the usage of renewable sources in the development of foamable polyamide materials for sustainable applications in the plastics industry.

Morphology and Crystallization of Biobased Polyamide 56 Blended with Polyethylene Terephthalate

AbstractThis study attempts to promote biobased polyamide 56 (PA56) as a sustainable candidate to replace commercial PA6 and PA66 when blended with polyethylene terephthalate (PET). Scanning and transmission electron microscopy of the blends with different PA56 contents reveals an immiscible morphology with an increase in the size of the dispersed domains by increasing PA56 content. The steady‐state mixing torque of the kneader is decreased to half by adding 10 wt% of PA56 to PET. Further addition of PA56 gradually increases this torque but does not surpass the neat PET sample up to 30 wt% of PA56. As revealed by microscopic dissipative particle dynamics (DPD) simulations, this gradual increase is ascribed to the difficulty to disperse larger domains of PA56 in the thermodynamically undesired PET. The results confirm that PA56 has a lubricating effect in PET. Using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD) techniques, it is shown that PA56 acts as a nucleating agent in PET. This leads to the formation of numerous small crystals in the blends as opposed to several large crystals in the neat samples. The results encourage the use of PA56 biomaterial in combination with PET in products such as bicomponent segmented pie fibers.

Novel Cystine Ester Mimics for the Treatment of Cystinuria-induced Urolithiasis in a Knockout Mouse Model

To assess the effectiveness of l-cystine dimethyl ester (CDME), an inhibitor of cystine crystal growth, for the treatment of cystine urolithiasis in an Slc3a1 knockout mouse model of cystinuria. CDME (200 μg per mouse) or water was delivered by gavage daily for 4 weeks. Higher doses by gavage or in the water supply were administered to assess organ toxicity. Urinary amino acids and cystine stones were analyzed to assess drug efficacy using several analytical methods. Treatment with CDME led to a significant decrease in stone size compared with that of the water group (P = .0002), but the number of stones was greater (P = .005). The change in stone size distribution between the 2 groups was evident by micro computed tomography. Overall, cystine excretion in urine was the same between the 2 groups (P = .23), indicating that CDME did not interfere with cystine metabolism. Scanning electron microscopy analysis of cystine stones from the CDME group demonstrated a change in crystal habit, with numerous small crystals. l-cysteine methyl ester was detected by ultra-performance liquid chromatography-mass spectrometer in stones from the CDME group only, indicating that a CDME metabolite was incorporated into the crystal structure. No pathologic changes were observed at the doses tested. These data demonstrate that CDME promotes formation of small stones but does not prevent stone formation, consistent with the hypothesis that CDME inhibits cystine crystal growth. Combined with the lack of observed adverse effects, our findings support the use of CDME as a viable treatment for cystine urolithiasis.

Flux growth of Sr2Ta2O7 crystals and subsequent nitridation to form SrTaO2N crystals

Highly crystalline, idiomorphic Sr2Ta2O7 and SrTaO2N crystals were successfully grown by a SrCl2 flux cooling method and followed by a nitriding treatment using NH3 gas, respectively. The flux-grown Sr2Ta2O7 crystals had a columnar structure with flat and well-developed {010}, {061}, and {150} faces. The lattice parameters of the Sr2Ta2O7 crystals were determined to be a = 0.398, b = 2.716, and c = 0.570 nm. The TEM images indicated that the flux-grown Sr2Ta2O7 crystals had a mature columnar structure with high crystallinity. The shapes and sizes of the SrTaO2N crystals were in good agreement with the original Sr2Ta2O7 crystals, and they consisted of numerous small crystals with approximate dimensions of 50 nm and high crystallinity. The lattice parameters of the SrTaO2N crystals were a = 0.570 and c = 0.809 nm. The optical absorption edges of the Sr2Ta2O7 and SrTaO2N crystals were approximately 275 and 600 nm, respectively, and the band gaps were estimated to be located at 4.5 and 2.1 eV, respectively.

On the importance of small ice crystals in tropical anvil cirrus

Abstract. In situ measurements of ice crystal concentrations and sizes made with aircraft instrumentation over the past two decades have often indicated the presence of numerous relatively small (< 50 μm diameter) crystals in cirrus clouds. Further, these measurements frequently indicate that small crystals account for a large fraction of the extinction in cirrus clouds. The fact that the instruments used to make these measurements, such as the Forward Scattering Spectrometer Probe (FSSP) and the Cloud Aerosol Spectrometer (CAS), ingest ice crystals into the sample volume through inlets has led to suspicion that the indications of numerous small-crystals could be artifacts of large-crystal shattering on the instrument inlets. We present new aircraft measurements in anvil cirrus sampled during the Tropical Composition, Cloud, and Climate Coupling (TC4) campaign with the 2-Dimensional Stereo (2D-S) probe, which detects particles as small as 10 μm. The 2D-S has detector "arms" instead of an inlet tube. Since the 2D-S probe surfaces are much further from the sample volume than is the case for the instruments with inlets, it is expected that 2D-S will be less susceptible to shattering artifacts. In addition, particle inter-arrival times are used to identify and remove shattering artifacts that occur even with the 2D-S probe. The number of shattering artifacts identified by the 2D-S interarrival time analysis ranges from a negligible contribution to an order of magnitude or more enhancement in apparent ice concentration over the natural ice concentration, depending on the abundance of large crystals and the natural small-crystal concentration. The 2D-S measurements in tropical anvil cirrus suggest that natural small-crystal concentrations are typically one to two orders of magnitude lower than those inferred from CAS. The strong correlation between the CAS/2D-S ratio of small-crystal concentrations and large-crystal concentration suggests that the discrepancy is likely caused by shattering of large crystals on the CAS inlet. We argue that past measurements with CAS in cirrus with large crystals present may contain errors due to crystal shattering, and past conclusions derived from these measurements may need to be revisited. Further, we present correlations between CAS spurious concentration and 2D-S large-crystal mass from spatially uniform anvil cirrus sampling periods as an approximate guide for estimating quantitative impact of large-crystal shattering on CAS concentrations in previous datasets. We use radiative transfer calculations to demonstrate that in the maritime anvil cirrus sampled during TC4, small crystals indicated by 2D-S contribute relatively little cloud extinction, radiative forcing, or radiative heating in the anvils, regardless of anvil age or vertical location in the clouds. While 2D-S ice concentrations in fresh anvil cirrus may often exceed 1 cm−3, and are observed to exceed 10 cm−3 in turrets, they are typically ~0.1 cm−3 and rarely exceed 1 cm−3 (<1.4% of the time) in aged anvil cirrus. We hypothesize that isolated occurrences of higher ice concentrations in aged anvil cirrus may be caused by ice nucleation driven by either small-scale convection or gravity waves. It appears that the numerous small crystals detrained from convective updrafts do not persist in the anvil cirrus sampled during TC-4.

Inclusions of silicate and sulfate melts in chrome diposide from the Inagli deposit, Yakutia, Russia

Melt inclusions were studied in chrome diopside from the Inagli deposit of gemstones in the Inagli massif of alkaline ultrabasic rocks of potassic affinity in the northwestern Aldan shield, Yakutia, Russia. The chrome diopside is highly transparent and has an intense green color. Its Cr2O3 content varies from 0.13 to 0.75 wt %. Primary and primary-secondary polyphase inclusions in chrome diopside are dominated by crystal phases (80–90 vol %) and contain aqueous solution and a gas phase. Using electron microprobe analysis and Raman spectroscopy, the following crystalline phases were identified. Silicate minerals are represented by potassium feldspar, pectolite [NaCa2Si3O8(OH)], and phlogopite. The most abundant minerals in the majority of inclusions are sulfates: glaserite (aphthitalite) [K3Na(SO4)2], glauberite [Na2Ca(SO4)2], aluminum sulfate, anhydrite (CaSO4), gypsum (CaSO4 × 2H2O), barite (BaSO4), bloedite [Na2Mg(SO4)2 × 4H2O], thenardite (NaSO4), polyhalite [K2Ca2Mg(SO4)4 × 2H2O], arcanite (K2SO4), and celestite (SrSO4). In addition, apatite was detected in some inclusions. Chlorides are probably present among small crystalline phases, because some analyses of aggregates of silicate and sulfate minerals showed up to 0.19–10.3 wt % Cl. Hydrogen was identified in the gas phase of polyphase inclusions by Raman spectroscopy. The composition of melt from which the chrome diopside crystallized was calculated on the basis of the investigation of silicate melt inclusions. This melt contains 53.5 wt % SiO2, considerable amounts of CaO (16.3 wt %), K2O (7.9 wt %), Na2O (3.5 wt %), and SO3 (1.4 wt %) and moderate amounts of Al2O3 (7.5 wt %), MgO (5.8 wt %), FeO (1.1 wt %), and H2O (0.75 wt %). The content of Cr2O3 in the melt was 0.13 wt %. Many inclusions were homogenized at 770–850°C, when all of the crystals and the gas phase were dissolved. The material of inclusions heated up to the homogenization temperature became heterogeneous even during very fast quenching (two seconds) producing numerous small crystals. This fact implies that most of the inclusions contained a salt (rather than silicate) melt of sulfate-dominated composition. Such inclusions were formed from salt globules (with a density of about 2.5 g/cm3) occurring as an emulsion in the denser (2.6 g/cm3) silicate melt from which the chrome diopside crystallized.

Effect of processing conditions on microstructure of milk fat fraction/sunflower oil blends

AbstractThe effect of processing conditions on the crystallization of blends of a high‐melting milk fat fraction and sunflower oil was investigated. Two cooling rates were selected for all studies: 0.1°C/min (slow rate) and 5.5°C/min (fast rate). Blends were crystallized in two conditions: (i) with agitation in an 80‐mL crystallizer (dynamic), and (ii) on a microscope slide without agitation (static). The selected crystallization temperatures were 25, 30, and 35°C for both cooling rates. Photographs of the development of crystals with time were taken in both static and dynamic conditions, and the crystal size distribution was determined at the moment that the laser signal reached its peak. Photographs showed that when samples were cooled slowly, crystals had a more regular boundary, appeared to be more densely arranged, and were larger. In dynamic conditions, crystal sizes were smaller and the background contained numerous small crystals, which were not found in statically crystallized samples. All images showed that crystals were not single crystals, but grew by accretion.

Radiative sensitivities of tropical anvils to small ice crystals

Stratiform anvils in the upper tropical troposphere were simulated to determine the sensitivities of their radiative properties to the presence of small ice crystals. Cloud evolution was modeled in a one‐dimensional (vertical) framework incorporating an updraft, deposition, sublimation, sedimentation, nucleation, and radiation. The sensitivities of cloud radiative forcing, albedo, emissivity, and heating rate were derived from a test that included and then excluded the presence of numerous small crystals. These crystals sizes (3 < L < 20 μm) have been measured in recent observations but are smaller than the detection limit of most past observations. The shortwave forcing and albedo were very sensitive to the presence of the small crystals, even though these crystals accounted for less than 2% of total cloud mass. For optically thick anvils the longwave forcing and emissivity were, in general, much less sensitive to the small ice crystals than their shortwave counterparts. Radiative treatments assuming a hexagonal crystal habit yielded the same sensitivities as the spherical habit. The results agreed with previous studies in that the increased backscatter from hexagonal crystals enhanced the planetary albedo by ∼10–15%. The heating rate sensitivity to the small crystals depended on vertical location within the cloud and showed cancelation between the longwave and the shortwave heating perturbations. The small crystals changed heating rates by up to 50% at cloud top and base.

The micromorphological distribution of bound calcium in needles of Norway spruce [Picea abies (L.) Karst.

The distribution of bound calcium in spruce needles is visualized by various microscopical techniques. Ca pectate occurs in the middle lamellae of cell walls and in a surprisingly great concentration in the thick cell walls of the sieve cells and transfusion parenchyma. The major fraction of the calcium, however, is bound in the form of insoluble Ca oxalate crystals, which occur extracellularly on the outside of the walls of mesophyll cells which face the intercellular spaces. Furthermore, numerous small crystals appear within the cell walls of the epidermal cells, especially in the cuticular layer. The development and distribution of these apoplastic crystals is described in detail. Some hypotheses are finally presented for possible interpretations of these unusual patterns of the crystallization of Ca oxalate outside the vacuole.

Comparative Microscopical Studies on the Patterns of Calcium Oxalate Distribution in the Needles of Various Conifer Species

AbstractThe distribution of calcium oxalate crystals in various conifer needles is visualized by light and electron microscopy. Such crystals occur (1) in the vascular bundle, either intracellularly in the xylem or phloem parenchyma, or extracellularly within the radial phloem walls; (2) extracellularly on the outside of the walls of mesophyll cells which face the intercellular spaces; (3) and finally as numerous small crystals within the cell walls of the epidermal cells, especially in the cuticular layer. The development and distribution of these apoplastic crystals is described in detail. Some hypotheses are finally presented for interpretations of these unusual patterns of the crystallization of Ca‐oxalate outside the vacuole. Possible evolutionary aspects of this feature among the different conifer families are also discussed.

Yttrium enrichment and improved magnetic properties in partially melted Y-Ba-Cu-O materials

Samples of Y-Ba-Cu-O materials with the formulation Y:Ba:Cu = x:2:3 and values of x ranging between 1 and 3 were prepared by partial melting at a maximum temperature of 1045 °C. Measurements of magnetic susceptibility and maximum (low-field) as well as remanent magnetization show highest values for x = 2. XRD and SEM/EDX analyses show that the corresponding structure involves numerous small crystals of Y2BaCuO5 (211) embedded in highly ordered assemblages of continuous YBa2Cu3O7−y (123) layers. The presence of these impurity sites is correlated with flux pinning capacity. Other impurity phases include CuO, a minor phase which shows an increase in amount when x increases, BaCuO3, a possibly detrimental minor phase which vanishes when x is raised from 1 to 2, and zones of intermediate composition between the 211 grains and the 123 layers, which are formed from the residual liquid upon cooling. These intermediate regions, like the 211 grains themselves, become gradually more important when x is increased from 1 to 3.

Wood Anatomy of Acanthaceae: A Survey

Qualitative and quantitative wood features are reported for 38 species representing 22 genera, including the scandent genera Mendoncia and Thunbergia. Woods of Acanthaceae are characterized by relatively narrow vessels with simple perforation plates and alternate lateral wall pitting, septate libriform fibers, scanty vasicentric axial parenchyma, rays both multiseriate and uniseriate, erect ray cells abundant in rays (some species rayless or near-rayless), numerous small crystals or cystoliths in ray cells in a few genera (first documented reports of both characters in woods of Acanthaceae), and nonstoried structure. This constellation of features is very closely matched by woods of Gesneriaceae, Scrophulariaceae, Pedaliaceae, Martyniaceae, Bignoniaceae, and Myoporaceae (families listed in order ofdecreasing resemblance). Narrowness ofvessels in tropical Acanthaceae appears related to understory ecology. A few species in warm and seasonally dry areas have narrow, short vessel elements numerous per unit transection. Vasicentric tracheids occur in two nonscandent genera in dry areas. Vessel grouping is roughly proportional to dryness of habitat. Thunbergia alata, T. laurifolia, and all collections of Mendoncia have interxylary phloem (first report for Mendoncia). That feature, plus presence of occasional acicular crystals in rays and axial parenchyma and presence of large gelatinous fibers in phloem ally Mendoncia closely with Thunbergia, and Mendonciaceae is not justified for this and other reasons. Species of Thunbergia differ among themselves, and T. erecta and T. holstii resemble shrubby Acanthaceae more than they do Mendoncia in wood features. Thunbergia thus should not be segregated from Acanthaceae.

Electrochemical Doping of Polycyanoacetylene, A New Conducting Polymer

Abstract Polycyanoacetylene was prepared by dehydrochlorination of poly-α-chloroacrylonitrile at low temperature. Thin films were simply obtained by spreading a DMF solution onto a stainless steel substrate. Transmission electron microscopy revealed a highly crystalline structure. Two different morphologies were observed : large isolated single crystals and numerous small crystals dispersed in the precursor matrix. The electrochemical behaviour of polycyanoacetylene was studied using a (-CH=C(CN)-) /(PEO)8LICIO4/Li cell. Cyclic voltammetry indicated a very reversible behaviour. Lithium intercalation/deintercalation occurred at ca 2.6 V vs Li/Li+. This high value compared to polyacetylene may be attributed to the electron withdrawing effect of the cyano- group. These properties make polycyanoacetylene suitable for use as a positive electrode in batteries.

Developmental features of calcium oxalate crystal sand deposition inBeta vulgaris L. Leaves

Sugar beet (Beta vulgaris L.) leaf has a layer of cells extended laterally between the palisade parenchyma and spongy mesophyll that develop numerous small crystals (crystal sand) within their vacuoles. Solubility studies and histochemical staining indicate the crystals are calcium oxalate. The crystals are deposited within the vacuoles early during leaf development, and at maturity the cells are roughly spherical in shape and 2 to 3 times larger than other mesophyll cells. Crystal deposition is preceeded by formation of membrane vesicles within the vacuole. The membranes are synthesizedde novo in the vacuole and have a typical trilaminate structure as viewed with the TEM. The membranes are formed within paracrystalline aggregates of tubular particles (6–8nm outer diameter) as membrane sheets, but are later organized into chambers or vesicles. Calcium oxalate is then precipitated within the membrane chambers. The tubular particles involved in membrane synthesis are usually present in the vacuoles of mature crystal cells, but in very small amounts.

Some new crystal-forms on Krennerite

Some interest attaches to crystals of krennerite, since this mineral has apparently the same composition as calaverite, the crystalline development of which presents such peculiar features. After completing the study of crystals of the latter substance, the author naturally turned his attention to krennerite to ascertain whether any similar peculiarities were noticeable, but nothing abnormal could be detected.Good crystals of krennerite are rare. The Mineral Collection of the British Museum has however a specimen from Nagyág, on which are dotted numerous small crystals possessing a large number of brilliant faces. This specimen was examined by Prof. H. A. Miers rather more than twelve years ago, and the measurements of one good crystal are recorded in this Magazine.