Hoà Phan - Academia.edu (original) (raw)

Papers by Hoà Phan

Analytical and bioanalytical chemistry, Jan 11, 2018

Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles a... more Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles are dispersed in various solvents and matrices. While extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory has been successfully applied to predict nanoparticle stability in solution, this model fails to accurately predict the physical stability of anisotropic nanostructures; thus limiting its applicability in practice. Herein, DLVO theory was used to accurately predict gold nanostar stability in solution by investigating how the choice of the nanostar dimension considered in calculations influences the calculated attractive and repulsive interactions between nanostructures. The use of the average radius of curvature of the nanostar tips instead of the average radius as the nanostar dimension of interest increases the accuracy with which experimentally observed nanoparticle behavior can be modeled theoretically. This prediction was validated by measuring time-dependent localized surfac...

Scientifica, 2018

Two types of lipase, lipase (CRL) and porcine pancreas lipase (PPL), were used to hydrolyze virgi... more Two types of lipase, lipase (CRL) and porcine pancreas lipase (PPL), were used to hydrolyze virgin coconut oil (VCO). The hydrolysis process was carried out under four parameters, VCO to buffer ratio, lipase concentration, pH, and temperature, which have a significant effect on hydrolysis of lipase. CRL obtained the best hydrolysis condition at 1 : 5 of VCO to buffer ratio, 1.5% of CRL concentration, pH 7, and temperature of 40°C. Meanwhile, PPL gave different results at 1 : 4 of VCO to buffer ratio, 2% of lipase concentration, pH 7.5, and 40°C. The highest hydrolysis degree of CRL and PPL was obtained after 16 hours and 26 hours, reaching 79.64% and 27.94%, respectively. Besides, the hydrolysis process was controlled at different time course (every half an hour) at the first 4 hours of reaction to compare the initial hydrolysis degree of these two lipase types. FFAs from hydrolyzed products were isolated and determined the percentage of each fatty acid which contributes to the FFAs...

Journal of lipids, 2017

Free fatty acids (FFAs) were obtained from hydrolyzed virgin coconut oil (VCO) by Candida rugosa ... more Free fatty acids (FFAs) were obtained from hydrolyzed virgin coconut oil (VCO) by Candida rugosa lipase (CRL). Four factors' influence on hydrolysis degree (HD) was examined. The best hydrolysis conditions in order to get the highest HD value were determined at VCO to buffer ratio 1 : 5 (w/w), CRL concentration 1.5% (w/w oil), pH 7, and temperature 40°C. After 16 hours' reaction, the HD value achieved 79.64%. FFAs and residual hydrolyzed virgin coconut oil (HVCO) were isolated from the hydrolysis products. They were tested for their antibacterial activity against Gram-negative and Gram-positive bacteria, which can be found in contaminated food and cause food poisoning. FFAs showed their inhibition against Bacillus subtilis (ATCC 11774), Escherichia coli (ATCC 25922), Salmonella enteritidis (ATCC 13076), and Staphylococcus aureus (ATCC 25923) at minimum inhibitory concentration (MIC) of 50%, 60%, 20%, and 40%, respectively. However, VCO and HVCO did not show their antibacteri...

Molecular Pharmacology, 2017

Regulator of G protein signaling 2 (RGS2) plays a significant role in alleviating vascular contra... more Regulator of G protein signaling 2 (RGS2) plays a significant role in alleviating vascular contraction and promoting vascular relaxation due to its GTPase accelerating protein activity toward Gaq. Mice lacking RGS2 display a hypertensive phenotype, and several RGS2 missense mutations have been found predominantly in hypertensive human subjects. However, the mechanisms whereby these mutations could impact blood pressure is unknown. Here, we selected 16 rare, missense mutations in RGS2 identified in various human exome sequencing projects and evaluated their ability to inhibit intracellular calcium release mediated by angiotensin II receptor type 1 (AT1R). Four of them had reduced function and were further investigated to elucidate underlying mechanisms. Low protein expression, protein mislocalization, and reduced G protein binding were identified as likely mechanisms of the malfunctioning mutants. The Q2L mutant had 50% lower RGS2 than wild-type (WT) protein detected by Western blot. Confocal microscopy demonstrated that R44H and D40Y had impaired plasma membrane targeting; only 46% and 35% of those proteins translocated to the plasma membrane when coexpressed with Ga q Q209L compared with 67% for WT RGS2. The R188H mutant had a significant reduction in Ga q binding affinity (10-fold increase in K i compared with WT RGS2 in a flow cytometry competition binding assay). This study provides functional data for 16 human RGS2 missense variants on their effects on AT1R-mediated calcium mobilization and provides molecular understanding of those variants with functional loss in vitro. These molecular behaviors can provide insight to inform antihypertensive therapeutics in individuals with variants having reduced function.

Journal of community genetics, Jan 11, 2017

Thalassemia is a genetic condition that can result in long and expensive treatments, and severe t... more Thalassemia is a genetic condition that can result in long and expensive treatments, and severe thalassemia may lead to death if left untreated. Couples contributing two genes for thalassemia place their children at particular risk for severe thalassemia. Gene frequency of thalassemia varies in Vietnam, but presents remarkably high levels among some ethnic minority groups. Limited information about thalassemia frequency makes prevention and control of thalassemia difficult. This study aimed to determine gene frequency of certain types of thalassemia among 390 women of reproductive age of the Ta-Oi ethnic minority. Hemoglobin and DNA analyses were carried out to diagnose thalassemia and hemoglobinopathies. Of the total participants, 56.1% (95% CI = 51.1-61.1) carried thalassemia genes. A remarkably high frequency of hemoglobin Constant Spring (Hb CS) of 23.8% (95% CI = 19.7-28.4) was noted. The frequency of α(+)-thalassemia (-3.7 kb deletion) was 26.4% (95% CI = 22.1-31.1), while hem...

Archaea, 2005

Three plasmids isolated from the crenarchaeal thermoacidophile Sulfolobus neozealandicus were cha... more Three plasmids isolated from the crenarchaeal thermoacidophile Sulfolobus neozealandicus were characterized. Plasmids pTAU4 (7,192 bp), pORA1 (9,689 bp) and pTIK4 (13,638 bp) show unusual properties that distinguish them from previously characterized cryptic plasmids of the genus Sulfolobus. Plasmids pORA1 and pTIK4 encode RepA proteins, only the former of which carries the novel polymerase-primase domain of other known Sulfolobus plasmids. Plasmid pTAU4 encodes a mini-chromosome maintenance protein homolog and no RepA protein; the implications for DNA replication are considered. Plasmid pORA1 is the first Sulfolobus plasmid to be characterized that does not encode the otherwise highly conserved DNA-binding PlrA protein. Another encoded protein appears to be specific for the New Zealand plasmids. The three plasmids should provide useful model systems for functional studies of these important crenarchaeal proteins.

Journal of Materials Chemistry C, 2015

A significant piezoresistive effect in p-type nanocrystalline SiC with a gauge factor of 14.5 was... more A significant piezoresistive effect in p-type nanocrystalline SiC with a gauge factor of 14.5 was reported. This result indicates that p-type nanocrystalline SiC is a good candidate for MEMS sensors used in harsh environments and bio applications.

J. Mater. Chem. C, 2014

The influence of crystal defects on the gauge factor of p-type single crystalline 3C-SiC thin fil... more The influence of crystal defects on the gauge factor of p-type single crystalline 3C-SiC thin films is reported.

Lecture Notes in Computer Science, 2009

Proceedings of the 2009 ACM symposium on Applied Computing - SAC '09, 2009

Environmental Microbiology, 2010

Lactobacillus plantarum is a ubiquitous microorganism that is able to colonize several ecological... more Lactobacillus plantarum is a ubiquitous microorganism that is able to colonize several ecological niches, including vegetables, meat, dairy substrates and the gastro-intestinal tract. An extensive phenotypic and genomic diversity analysis was conducted to elucidate the molecular basis of the high flexibility and versatility of this species. First, 185 isolates from diverse environments were phenotypically characterized by evaluating their fermentation and growth characteristics. Strains clustered largely together within their particular food niche, but human fecal isolates were scattered throughout the food clusters, suggesting that they originate from the food eaten by the individuals. Based on distinct phenotypic profiles, 24 strains were selected and, together with a further 18 strains from an earlier low-resolution study, their genomic diversity was evaluated by comparative genome hybridization against the reference genome of L. plantarum WCFS1. Over 2000 genes were identified that constitute the core genome of the L. plantarum species, including 121 unique L. plantarum-marker genes that have not been found in other lactic acid bacteria. Over 50 genes unique for the reference strain WCFS1 were identified that were absent in the other L. plantarum strains. Strains of the L. plantarum subspecies argentoratensis were found to lack a common set of 24 genes, organized in seven gene clusters/operons, supporting their classification as a separate subspecies. The results provide a detailed view on phenotypic and genomic diversity of L. plantarum and lead to a better comprehension of niche adaptation and functionality of the organism.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011

Magnetic heating effect of Fe3O4 ferrofluids, surface-carboxylated and encapsulated by poly(styre... more Magnetic heating effect of Fe3O4 ferrofluids, surface-carboxylated and encapsulated by poly(styrene-acrylic acid) was studied. Magnetic Fe3O4 NPs were synthesized by coprecipitation method and characterized by X-ray diffraction (XRD), Field Emission Electron Microscope (FESEM) and Vibrating Sample Magnetometer (VSM). Spectroscopic data (Infra red (IR) and Proton Nuclear Magnetic Resonance (1H NMR) spectra) confirmed that Fe3O4 NP surface was carboxylated and capable

Understanding the cooperative effects, such as electron-lattice interactions, in moleculebased ma... more Understanding the cooperative effects, such as electron-lattice interactions, in moleculebased magnetic coordination complexes possessing photoinduced phase transitions is an important step to being able to rationally tune the variables governing the process. 2 Specifically, variable temperature FTIR spectroscopy and magnetometry have been used to explore the temperature and photocontrollable spin transitions in Co-Fe Prussian blue analogues, A j Co k [Fe(CN) 6 ] ℓ • nH 2 O, where A is an alkali ion, and in new Fe spin-crossover complexes. By studying nanoparticles 3 and heterostructures, 4 the data provide insight into the roles played by restricted lattice geometries and strain-pressure effects.

Analytica Chimica Acta, 2001

A recently developed technique measures near-field surface-enhanced Raman spectra with 100-nm res... more A recently developed technique measures near-field surface-enhanced Raman spectra with 100-nm resolution, enabling a fast survey on the sample surface. This technique has two bottlenecks. One is a general problem: signal changes are attributed to either the sample composition or the substrate morphology. Therefore, it is mandatory to detect even small signal changes in order to distinguish between these two effects. Secondly, huge data amounts make the spectrum interpretation tedious. How to find the interesting and important information? To investigate these problems, a sample, containing dye-labeled DNA-fragments that are drop-coated onto a silver island substrate, is measured. The enhanced Raman spectra yield indirect information on the DNA-fragments. The goal of this investigation is to provide a tool that allows a fast and reliable spectral analysis. Is it possible to distinguish local differences in the sample composition and to correlate them with the sample morphology? A general explorative data analyses tool, principal component analysis (PCA), is used for a first investigation. PCA has a useful side-effect: spikes, well-known artifacts, are also detected. After removing these artifacts, PCA facilitated the detection of three neighboring spectra, clearly deviating from the others. Probably, the DNA double-strand unfolded and generated a direct Raman-signal. The automated PCA-procedure gives identical results. It is concluded that a general explorative tool can solve two major difficulties. Application of dedicated chemometrical tools could improve the results. The combination of chemometrics and this new technique is powerful and promising.

Remote Sensing, 2021

Rice is the primary staple food of more than half of the world’s population and plays an especial... more Rice is the primary staple food of more than half of the world’s population and plays an especially important role in global economy, food security, water use, and climate change. The usefulness of Synthetic Aperture Radars (SAR) for rice mapping and monitoring has been demonstrated locally in many studies, in particular in the last five years with the availability of an unprecedented amount of free Sentinel-1 data within the Copernicus program. However, although earlier studies from the 1990s have laid the foundations of the physical understanding of the SAR response of rice fields, the more recent studies tend to overlook this aspect and to favor instead approaches driven by supervised learning which provide accurate results locally but cannot necessarily be extended to wide areas. The objective of this study is to analyze in detail the backscatter temporal variation of rice fields, using Sentinel-1 from 2015 to 2020 and in-situ data for the 5 rice seasons over 2 years 2017–2018, ...

Chemical science, Jan 14, 2018

So far, most reported open-shell singlet diradicaloids are based on planar π-conjugated molecules... more So far, most reported open-shell singlet diradicaloids are based on planar π-conjugated molecules. Herein, we report the bridged corannulene dimer diradicaloids, and , both showing a three-dimensional curved π-conjugated structure. has a small diradical character ( = 5.4%) and behaves more like a closed-shell quinoidal compound at room temperature, while is a typical open-shell diradicaloid with a larger diradical character ( = 16.9%). Both compounds exhibited paramagnetic activity at elevated temperatures, with a singlet-triplet energy gap (Δ) of -8.4 and -3.0 kcal mol, respectively. X-ray crystallographic analysis revealed that both molecules have a dumbbell-shaped geometry, with the two terminal corannulene bowls bent to opposite directions. The spin is largely delocalized onto the two bowls in and there are multiple [CH···π] interactions between the neighboring bowls. Chemical oxidation/reduction to their respective dications/dianions results in global aromaticity with [4 + 2] π...

Inorganic chemistry, Jan 7, 2018

Homoleptic complexes [Fe(L )]X (L = 1,1'-(α,α'- o-xylyl)-2,2'-biimidazole, L = 1,1&#3... more Homoleptic complexes [Fe(L )]X (L = 1,1'-(α,α'- o-xylyl)-2,2'-biimidazole, L = 1,1'-(α,α'-3,4-dibromo- o-xylyl)-2,2'-biimidazole, L = 1,1'-(α,α'-2,5-dimethoxy- o-xylyl)-2,2'-biimidazole; X = BF or ClO) were synthesized by direct reactions of the Fe(II) precursor salts and bidentate ligands L, L, or L. All mononuclear complexes undergo gradual temperature-driven spin-crossover (SCO) between the high-spin (HS, S = 2) and low-spin (LS, S = 0) states. Complexes with ligands L and L synthesized in methanol exhibit complete SCO with the midpoint of the LS↔HS conversion varying from 233 to 313 K, while complexes with ligand L, crystallized from an ethanol/dichloromethane mixture, exhibit incomplete SCO with the residual HS/LS ratio of ∼1:4 for [Fe(L)](BF) and ∼1:1 for [Fe(L)](ClO). Complexes with L can also be recrystallized from ethanol/dichloromethane, in which case they exhibit very gradual and incomplete SCO, similar to those of the complexes with L....

Sensors (Basel, Switzerland), Jan 22, 2018

Rice is a major staple food for nearly half of the world's population and has a considerable ... more Rice is a major staple food for nearly half of the world's population and has a considerable contribution to the global agricultural economy. While spaceborne Synthetic Aperture Radar (SAR) data have proved to have great potential to provide rice cultivation area, few studies have been performed to provide practical information that meets the user requirements. In rice growing regions where the inter-field crop calendar is not uniform such as in the Mekong Delta in Vietnam, knowledge of the start of season on a field basis, along with the planted rice varieties, is very important for correct field management (timing of irrigation, fertilization, chemical treatment, harvest), and for market assessment of the rice production. The objective of this study is to develop methods using SAR data to retrieve in addition to the rice grown area, the sowing date, and the distinction between long and short cycle varieties. This study makes use of X-band SAR data from COSMO-SkyMed acquired fr...

Journal of the American Chemical Society, Nov 13, 2017

Despite the great potential of heteroatom-contained polycyclic aromatic hydrocarbons in organic o... more Despite the great potential of heteroatom-contained polycyclic aromatic hydrocarbons in organic optoelectronics, there are very limited reports on hetero-aromatics containing B-N-B bond in the π-scaffold. Herein, stable 1,9-dibora-9a-azaphenalenyl (DBAP) derivatives, named as BNB-embedded phenalenyls, are presented. The DBAP skeleton contains a three-center two-π-electron B-N-B moiety with total 12 π-electrons and can be regarded as the isoelectronic structure of phenalenyl cation. Chemical reduction of the phenyl derivative of DBAP by potassium generated the dianion containing 14 delocalized π-electrons, which can be regarded as isoelectronic structure of phenalenyl anion. The dianion is sandwiched and stabilized by two bulky [K([18]crown-6)]+ counter ions according to its X-ray structure. However, its monoanion (an isoelec-tronic structure of phenalenyl radical) generated by mixing equal mole of neutral compound and dianion gave an unusual B-N-B embedded benzo[cd]fluoranthene dian...

Journal of the American Chemical Society, 2017

We propose a simple method for predicting the spin state of homoleptic complexes of the Fe(II) d ... more We propose a simple method for predicting the spin state of homoleptic complexes of the Fe(II) d 6 ion with chelating diimine ligands. The approach is based on the analysis of a single metric parameter within a free (noncoordinated) ligand: the interatomic separation between the N-donor metal-binding sites. An extensive analysis of existing complexes allows the determination of critical N•••N distances that dictate the regions of stability for the high-spin and lowspin complexes, as well as the intermediate range in which the magnetic bistability (spin crossover) can be observed. The prediction has been tested on several complexes that demonstrate the validity of our method.