Search Results (92)

Water shortage has been a serious issue for many years. Hydrate-based desalination (HBD) technology is a potential candidate for this solution. The present study investigates the use of Cyclopentane (CP) as a hydrate former for desalination through crystallization at low temperatures and atmospheric pressure. The primary objective of this work is to provide phase equilibrium data for CP hydrates (CPH) in the presence of novel salt systems, including NaBr, KBr, K₂SO₄, NaBr–KBr, NaCl–NaBr, KCl–KBr, Na₂SO₄–K₂SO₄, and CaCl₂–MgCl₂. Phase equilibrium temperatures were determined using both rapid and slow dissociation procedures. The van der Waals and Platteeuw-based Kihara (Kihara) approach, Hu-Lee-Sum (HLS) correlation, Standard Freezing Point Depression (SFPD) approach, and Activity-Based Occupancy Correlation (ABOC) were applied to model these new experimental data. The experimental results demonstrate that the differences between the quick and slow procedure data range from 0 °C to 1.2 °C. In addition, the increasing salt concentration enhances the inhibitory effect on hydrate formation. Furthermore, the influence of cations on the equilibrium temperature follows the decreasing order of Mg²⁺ > Ca²⁺ > Na⁺ > K⁺. In terms of halide anions, Br⁻ exhibits a stronger impact on equilibrium temperature compared to Cl⁻. The thermodynamic modeling results (for all four models) show good agreement with the experimental data with the average absolute deviation (AAD) of less than or equal to 0.79 °C. The ABOC approach proves to be the most effective among the four methods evaluated for accurately reproducing the equilibrium temperature of CPH, with AAD less than or equal to 0.38 °C. Full article

Background/Objectives: Naegleria fowleri is a free-living amoeba that invades brain tissues causing fatal primary amoebic meningoencephalitis (PAM). An effective and tolerable therapeutic agent is still lacking. Methods: A series of conformationally restricted analogs of miltefosine with varied restriction positions, stereochemical configuration and lengths of alkyl chain was investigated to discover more effective and less toxic agents than miltefosine. Results: Among tested compounds, derivatives 2a, 3b and 3d featuring 1,2- or 2,3-positional restriction with trans-configuration and tridecyl or behenyl alkyl chains were discovered as more potent and less cytotoxic agents. Compounds 2a, 3b and 3d elicited 3.49-, 3.58- and 6.03-fold relative potencies to miltefosine and 7.53, 3.90 and 3.49 selectivity indices, respectively. Furthermore, compounds 2a and 3b showed IC₉₀ values for N. fowleri lower than CC₅₀ against glial C6 cells. Compounds 2a, 3b and 3d induced morphological changes and programmed cell death of N. fowleri via the apoptosis-like pathway. The induced death of N. fowleri involved DNA fragmentation along with the loss of mitochondrial membrane potential. Conclusions: The current research presents compounds 2a and 3b as more potent, selective and effective agents than miltefosine against N. fowleri for further development. Full article

Within the energy sector, the potential to effectively harness the considerable energy present in gas turbine waste heat via an organic Rankine cycle (ORC) could markedly improve overall energy efficiency. This investigation centers on a printed-circuit heat exchanger (PCHE) utilizing cyclopentane as the working fluid. The study employs a combination of experimental techniques and computational fluid dynamics (CFD) simulations to conduct an in-depth analysis of the PCHE’s performance, leading to the successful development of a highly accurate heat-transfer correlation. A thorough comparison of experimental and simulation data is carried out to examine the temperature and pressure distributions within the heat exchanger. The maximum deviation between experimental and correlation-estimated data is within 20% (hot fluid: 15%; cold fluid: 18%). These findings offer essential theoretical insights and practical guidance for optimizing and ensuring the stable operation of waste-heat recovery systems. Full article

Background: Ten new sesquiterpenes, including eight eremophilane-type sesquiterpenes (1–8) and two compounds (9–10) with a cyclopentane ring, representing an undescribed subtype of sesquiterpene, along with a new abietane-type diterpenoid (11), were isolated and identified from a deep-sea-derived fungus: Eutypella sp. Methods: Their structures were elucidated on the basis of various spectroscopic analyses, mainly including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HRESIMS) data, ¹³C NMR calculations with DP4+ probability analyses, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction experiments. Results: Furthermore, compound 11 exhibited potent immunosuppressive activity with IC₅₀ values of 8.99 ± 1.08 μM in a lipopolysaccharide (LPS) model and 5.39 ± 0.20 μM in a concanavalin A (ConA) model. Full article

Leukemia, one of the major causes of cancer death, ranks 11th worldwide among cancer-related deaths. The current treatment of leukemia faces challenges recently due to a high burden of side effects. It is well established that curcumin has anticancer and tumor-suppressing activities in several cancers in addition to leukemia. Accordingly, 15 derivatives were designed and prepared to improve the shortcomings of curcumin, such as poor aqueous solubility, chemical instability, and low bioavailability. All 15 were evaluated for cytotoxicity against the leukemic cell line MOLT-4, which led to the prioritization and further evaluation of compound curcuminoid (2E,5E)-2,5-bis((3-(4-nitrophenyl)-1-phenyl-1H-pyrazol-4-yl)methylene)cyclopentan-1-one 5i. 5i. Compared to curcumin, 5i was significantly more effective in inducing mitochondrial dysfunction in MOLT-4 cells; hence increased ROS production and cytotoxicity. Treatment groups showed change in mitochondrial membrane potential by flow cytometry analysis. Moreover, tumor volume reduction observed with 5i treatment in Dalton’s Lymphoma model was accompanied with low toxicity. Intrinsic pathways of apoptosis was initiated by compound 5i that lowered Bcl-2 expression while augmenting cytochrome c, Bak and Bax levels both in vivo and in vitro. These results showcase the potent antiproliferative as well as cytotoxic effects of 5i at nanomolar doses against leukemia being at least 60 times more effective than curcumin. Full article

A ne stereocontrolled nitro sugar-mediated synthesis of polyhydroxylated β-amino acids is reported. The key step of this approach is a Michael addition of the lithium salt of tris(phenylthio)methane (a carboxyl synthetic equivalent) to sugar nitro olefins. This is followed by the generation of the amino acid functionality by the transformation of the tris(phenylthio)methyl substituent into the carboxylic acid functionality and the reduction of the nitro group to an amino group. Full article

The new chiral and configurationally stable cyclopentadienyl amidinate (CPAM) hafnium complexes, (R_C, R_Hf)-2 and (S_C, S_Hf)-3, have been obtained in enantio- and diastereomerically pure form. Upon activation with the borate co-initiator, [PhNHMe₂][B(C₆F₅)₄] (B1), 2 and 3 can serve as pre-initiators for the enantioselective living coordinative polymerization (LCP) and living coordinative chain transfer polymerization (LCCTP) of 1,5-hexadiene to provide optically active poly (methylene-1,3-cyclopentane) (PMCP) and end-group-functionalized PMCP (x-PMCP) in scalable quantities, respectively. ¹³C NMR stereochemical microstructural analyses reveal the role of ligand directing effects for the two-step propagation mechanism of 1,2-migratory insertion/ring-closing cyclization and structure/property relationships for these new PMCP and x-PMCP materials. Full article

This study investigates the palladium-catalyzed one-pot synthesis of functionalized furans from 1,3-Dicarbonyl compounds and alkenyl bromides, focusing on various catalysts and reaction parameters. Different catalysts, including PdCl₂(CH₃CN)₂, Pd(OAc)₂, and Pd(acac)₂ as well as solvents, bases, and oxidants, were systematically evaluated. PdCl₂(CH₃CN)₂ emerged as the most effective catalyst, achieving a remarkable yield of 94%. Optimal reaction conditions were identified as PdCl₂(CH₃CN)₂ in dioxane at 80 °C with K₂CO₃ as the base and CuCl₂ as the oxidant. This study also explored various 1,3-diketones including Cyclohexane-1,3-dione, 5,5-Dimethylcyclohexane-1,3-dione, 2H-Pyran-3,5(4H,6H)-dione, Cyclopentane-1,3-dione, Pentane-2,4-dione, Ethyl 3-oxobutanoate, 1,3-Diphenylpropane-1,3-dione, 1,3-Dip-tolylpropane-1,3-dione, 1,3-Bis(4-chlorophenyl)propane-1,3-dione, and 1,3-Bis(4-bromo- phenyl)propane-1,3-dione, alongside different alkenyl bromides such as allyl bromide, (E)-1-Bromo-3,4-dimethylpent-2-ene, 1-Bromo-3-methylbut-2-ene, 3-Bromocyclohex-1-ene, and (E)-1-Bromohex-2-ene. These variations demonstrated the method’s versatility and the significant impact of substituents on reactivity and reaction yield. These findings highlight the importance of optimizing reaction conditions to maximize efficiency and provide insights into improving catalytic processes for enhanced product yields. Full article

The supported Ni-P catalysts (marked as s-Ni-P/Hβ(3) and s-Ni-P/Ce-β(3)) were prepared by an incipient wetness step-impregnation method, and characterized by XRD, N₂ physisorption, TEM, XPS, and NH₃-TPD. The catalytic hydrodeoxygenation (HDO) performance was assessed using phenol in water (5.0 wt%) or in decalin (1.0 wt%) as the feed. After the introduction of Ce, the conversion of phenol increased due to the high dispersity of the active site. However, compared to s-Ni-P/Hβ(3), the amount of total and strong acid sites of s-Ni-P/Ce-β(3) decreased, restraining the cycloisomerization of cyclohexane to form methyl-cyclopentane. Moreover, the kinetics of the APHDO and OPHDO of phenol catalyzed by s-Ni-P/Hβ(3) and s-Ni-P/Ce-β(3) were investigated. Full article

Carbon dioxide (CO₂) has been recognized as one of the potential working fluids to operate power generation cycles, either in supercritical or transcritical configuration. However, a small concentration of some of the additives to CO₂ have shown promising improvements in the overall performance of the cycle. The current study is motivated by the newly proposed additive silicon tetrachloride (SiCl₄), and so we perform a detailed investigation of SiCl₄ along with a few well-known additives to CO₂-based binary mixtures as a working fluid in transcritical organic Rankine cycle setup with internal heat regeneration. The additives selected for the study are pentane, cyclopentane, cyclohexane, and silicon tetrachloride (SiCl₄). A comprehensive study on the energy and exergy performance of the cycle for warm regions is conducted at a turbine inlet temperature of 250 °C. The performance of the heat recovery unit is also assessed to highlight its importance in comparison to a simple configuration of the cycle. This study shows that the cycle operating with binary mixtures performs significantly better than with pure CO₂, which is mainly due to its better heat recovery in the heat recovery unit. The results show that the optimal molar concentration of the additives is in between 20% and 25%. Besides having better thermal stability, SiCl₄ shows an improvement in the cycle thermal efficiency by 6% points which is comparable to cyclopentane (7.3% points) and cyclohexane (7.8% points). The optimal cycle pressure ratio for SiCl₄ is also relatively lower than for other additives. The energy efficiency of the cycle with pure CO₂ is around 45% which is also increased to 58%, 63%, 64%, 60% with pentane, cyclopentane, cyclohexane, and SiCl₄, respectively. These results suggest that additives like SiCl₄ could make CO₂-based cycles more viable for power generation in warm regions. Full article

Waste heat recovery from exhaust gas is one of the most convenient methods to save energy in internal combustion engine-driven vehicles. This paper aims to investigate a reduction in waste heat from the exhaust gas of an internal combustion engine of a serial Diesel–electric hybrid bus by recovering part of the heat and converting it into useful power with the help of a split-flow supercritical CO₂ (sCO₂) recompression Brayton cycle. It can recover 17.01 kW of the total 33.47 kW of waste heat contained in exhaust gas from a 151 kW internal combustion engine. The thermal efficiency of the cycle is 38.51%, and the net power of the cycle is 6.55 kW. The variation in the sCO₂ temperature at the shutdown of the internal combustion engine is analyzed, and a slow drop followed by a sudden and then a slow drop is observed. After 80 s from stopping the engine, the temperature drops by (23–33)% depending on the tube thickness of the recovery heat exchanger. The performances (net power, thermal efficiency, and waste heat recovery efficiency) of the split-flow sCO₂ recompression Brayton cycle are clearly superior to those of the steam Rankine cycle and the organic Rankine cycle (ORC) with cyclopentane as a working fluid. Full article

Ovarian cancer (OC) is one of the most lethal gynecologic cancers that is typically diagnosed at the very late stage of disease progression. Thus, there is an unmet need to develop diagnostic probes for early detection of OC. One approach may rely on RNA as a molecular biomarker. In this regard, FLJ22447 lncRNA is an RNA biomarker that is over-expressed in ovarian cancer (OC) and in cancer-associated fibroblasts (CAFs). CAFs appear early on in OC as they provide a metastatic niche for OC progression. FIT-PNAs (forced intercalation-peptide nucleic acids) are DNA analogs that are designed to fluoresce upon hybridization to their complementary RNA target sequence. In recent studies, we have shown that the introduction of cyclopentane PNAs into FIT-PNAs (cpFIT-PNA) results in superior RNA sensors. Herein, we report the design and synthesis of cpFIT-PNAs for the detection of this RNA biomarker in living OC cells (OVCAR8) and in CAFs. cpFIT-PNA was compared to FIT-PNA and the cell-penetrating peptide (CPP) of choice was either a simple one (four L-lysines) or a CPP with enhanced cellular uptake (CLIP6). The combination of CLIP6 with cpFIT-PNA resulted in a superior sensing of FLJ22447 lncRNA in OVCAR8 cells as well as in CAFs. Moreover, incubation of CLIP6-cpFIT-PNA in OVCAR8 cells leads to a significant decrease (ca. 60%) in FLJ22447 lncRNA levels and in cell viability, highlighting the potential theranostic use of such molecules. Full article

In this study, polyurethane-polystyrene composites (RPURF-EPS) were obtained with the co-expansion method. This method consists of utilizing the heat of the exothermic reaction of polyurethane (PUR) formation to expand polystyrene beads (PSBs). The materials were obtained using polyurethane systems based on the selected blowing agents, such as cyclopentane, a mixture of fluorocarbons and water. The analysis of the foaming process was carried out using a special device called FOAMAT. The characteristic start, rise, gelation and curing times were defined. The rise profile, the reaction temperature, the pressure and the dielectric polarization were measured. The influence of selected blowing agents on the cell structure and physical–mechanical properties of reference rigid polyurethane foam (RPURF) and RPURF-EPS, such as apparent density, compressive strength and thermal conductivity, were evaluated. Based on the research, the blowing agents that have the most beneficial influence on the properties and structure of the composites and that provide the most efficient expansion of PSBs in a light porous composite were found. Full article

Isatropolone C from Streptomyces sp. CPCC 204095 features a fused cyclopentadienone-tropolone-oxacyclohexadiene tricyclic moiety in its structure. Herein, we report an isatropolone C dimer derivative, di-isatropolone C, formed spontaneously from isatropolone C in methanol. Notably, the structure of di-isatropolone C resolved by NMR reveals a newly formed cyclopentane ring to associate the two isatropolone C monomers. The configurations of four chiral carbons, including a ketal one, in the cyclopentane ring are assigned using quantum NMR calculations and DP4+ probability. The plausible molecular mechanism for di-isatropolone C formation is proposed, in which complex dehydrogenative C-C bond coupling may have happened to connect the two isatropolone C monomers. Like isatropolone C, di-isatropolone C shows the biological activity of inducing autophagy in HepG2 cells. Full article

One gravity core retrieved from the Niger Delta was used to explore the origin of deposited organic matter (OM) and the paleo-climatic and environmental conditions over the Holocene in equatorial West Africa. The geochemical properties of sediments including glycerol dialkyl glycerol tetraethers (GDGTs) and elemental (%OC, %N, C/N) and isotopic (δ¹³C_org, δ¹⁵N) signatures were determined. The determination constrained the age of the column and revealed that the sediment OM was mainly derived from a marine source. The isoprenoid (iso)GDGTs were the dominant GDGTs, with a small amount of branched (br)GDGTs, which led to a low-branched and isoprenoid tetraether index (BIT, 0.02–0.21) and represented a low terrestrial input. Most isoGDGTs and OH-GDGTs were produced in situ by Marine Group I (MG-I) Thaumarchaeota, while the brGDGTs were mainly transported from land. A two-endmember model quantified the contribution of terrestrial OM, as 0.9–19.9% by BIT and 1.1–32.6% by δ¹³C. Accordingly, the millennium-scale sea surface temperatures (SSTs) were reconstructed based on the cyclopentane ring distribution (${\mathrm{T}\mathrm{E}\mathrm{X}}_{86}^{\mathrm{H}}$) and the ring index of OH-GDGTs (RI-OH). The top core SSTs were lower than the modern mean annual SST due to the growth season and habitat depth of Thaumarchaeota. The reconstructed SSTs clearly revealed the four stages of paleoclimate change, in particular, the drought episode of 8.2 kyr and the following humid period. The above research has enhanced our understanding of the paleoclimate change in river outflow during the Holocene at the millennium scale. Full article