Publications by authors named "Ronghui Ma"

16 Publications

  • Page 1 of 1

Evaluation of Stem Engagement Activities On the Attitudes and Perceptions of Mechanical Engineering S-STEM Scholars.

J Biomech Eng 2021 Jul 10. Epub 2021 Jul 10.

Department of Mechanical Engineering.

Since 2009, the ME STEM Program at the University of Maryland Baltimore County has provided financial support and program activities to ME undergraduate students aiming at improving their retention and graduation rates. The objective of this study is to identify program activities that were most effective to help students for improvements. Current ME S-STEM scholars were asked to complete a survey that measures their scientific efficacy, engineering identity, expectations, integration, and sense of belonging, as well as how program activities impact their attitudes and perceptions. Analyses of 36 surveys showed that scholars reported high levels of engineering identity, expectations, and sense of belonging. However, further improvements were needed to help students in achieving scientific efficacy and academic integration into the program. Results demonstrated that proactive mentoring was the most effective method contributing to positive attitudes and perceptions. The implemented S-STEM research-related activities and internship were viewed favorably by the scholars in helping them establish their scientific efficacy and engineering identity, and understand their expectations and goals. Community building activities were considered helpful for them to integrate into campus life and improve their sense of belonging to the campus and program. Scholars identified mentoring, research related activities, internships, and social interaction with faculty and their peers as important factors for their retention and graduation. Although the sample size was small in the study, we believe that the cost-effective activities identified could be adopted by other institutions to further improve students' retention and graduation rates in engineering programs.
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http://dx.doi.org/10.1115/1.4051715DOI Listing
July 2021

Combined Treatment of Cinobufotalin and Gefitinib Exhibits Potent Efficacy against Lung Cancer.

Evid Based Complement Alternat Med 2021 20;2021:6612365. Epub 2021 Mar 20.

Department of Respiratory Neurology, The Affiliated Tumor Hospital of Xinjiang Medical University, Urumqi 830000, China.

This study aimed to evaluate the efficacy of cinobufotalin combined with gefitinib in the treatment of lung cancer. A549 cells were treated with gefitinib, cinobufotalin, or cinobufotalin plus gefitinib. MTT assay, annexin-V/PI staining and flow cytometry, TUNEL staining, DCFH-DA staining, Western blot, and real-time RT-PCR were performed to investigate the synergistic inhibitory effect of cinobufotalin combined with gefitinib on the growth of A549 cells. Results showed that cinobufotalin synergized with gefitinib displayed inhibited cell viability and enhanced apoptosis in the combination group. Cinobufotalin combined with gefitinib induced a significant enhancement in reactive oxygen species (ROS) production accompanied by cell cycle arrest in the S phase arrest, characterized by upregulation of p21 and downregulation of cyclin A, cyclin E, and CDK2. Besides, cinobufotalin plus gefitinib downregulated the levels of HGF and c-Met. In summary, cinobufotalin combined with gefitinib impedes viability and facilitates apoptosis of A549 cells, indicating that the combined therapy might be a new promising treatment for lung cancer patients who are resistant to gefitinib.
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http://dx.doi.org/10.1155/2021/6612365DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8189783PMC
March 2021

Theoretical evaluation of enhanced gold nanoparticle delivery to PC3 tumors due to increased hydraulic conductivity or recovered lymphatic function after mild whole body hyperthermia.

Med Biol Eng Comput 2021 Feb 11;59(2):301-313. Epub 2021 Jan 11.

Department of Mechanical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD, 21250, USA.

The objective of this study is to investigate the effect of hyperthermia-induced improvement of hydraulic conductivity and lymphatic function on both tumoral IFP reduction and nanoparticle delivery to PC3 tumors. We developed a theoretical model for nanoparticle transport in a tumor incorporating Starling's law, Darcy's law, transient convection, and diffusion of chemical species in porous media, and nanoparticle accumulation in tumors. Results have shown that both mechanisms were effective to decrease the IFP at the tumor center from 1600 Pa in the control without heating to 800 Pa in tumors with whole body heating. IFP reductions not only elevate the nanoparticle concentration in the tumor, but also result in a more uniform nanoparticle concentration in the tumor than that in the control without heating. Due to the IFP reductions at the tumor center and/or local blood perfusion increases, the final amount of accumulated nanoparticles in the tumor increased by more than 35-95% when compared to the control without heating. We conclude that increases in the hydraulic conductivity and recovery of lymphatic functions are possible mechanisms that lead to IFP reductions and enhancement in nanoparticle deposition in PC3 tumors observed in our in vivo experimental studies.
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http://dx.doi.org/10.1007/s11517-020-02308-4DOI Listing
February 2021

Establishing the Need to Broaden Bioengineering Research Exposure and Research Participation in Mechanical Engineering and Its Positive Impacts on Student Recruitment, Diversification, Retention and Graduation: Findings From the UMBC ME S-STEM Scholarship Program.

J Biomech Eng 2020 11;142(11)

Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250.

The objectives of this study were to evaluate the current status of exposure to bio-engineering research in community college (CC) students and University of Maryland Baltimore County (UMBC) students, and to estimate relationships between research activities sponsored by the Mechanical Engineering (ME) S-STEM Scholarship Program and improvement in student enrollment/diversification, retention rates, and graduation rates. The analysis drew on data from ME undergraduate academic records at UMBC from 2008 to 2019. A survey was designed to assess the research exposure of CC and UMBC students and their evaluation of the research components included in recruitment and curriculum activities. Results show that exposure to research measured by attending a research seminar was low for the participants, around 37% for CC students and 21% for ME students at UMBC. The survey results indicate the positive impact of the scholarship programs at UMBC on the research exposure and research experience. The impact is more evident in students who originally transferred from a CC. The large increase in recruited female and CC students over the past 10 years indicated that the research-related activities of the ME S-STEM program played an instrumental role in those increases. Because of the research-related activities, the ME S-STEM program achieved retention and graduation rates higher than those in the ME undergraduate program (89% versus 60% for the 6 year graduation rate), as well a higher percentage of students enrolled in graduate school (30% versus 10%). We conclude that there is still a need to implement research-related activities in the ME undergraduate program, starting with student recruitment and continuing through the academic program. Results suggest that there is a positive impact of ME S-STEM research activities on student diversification, retention rates, and percentage of our graduates who are pursuing graduate degree.
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http://dx.doi.org/10.1115/1.4047839DOI Listing
November 2020

Investigation of Biotransport in a Tumor With Uncertain Material Properties Using a Nonintrusive Spectral Uncertainty Quantification Method.

J Biomech Eng 2017 Sep;139(9)

Department of Mechanical Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250 e-mail:

In this study, statistical models are developed for modeling uncertain heterogeneous permeability and porosity in tumors, and the resulting uncertainties in pressure and velocity fields during an intratumoral injection are quantified using a nonintrusive spectral uncertainty quantification (UQ) method. Specifically, the uncertain permeability is modeled as a log-Gaussian random field, represented using a truncated Karhunen-Lòeve (KL) expansion, and the uncertain porosity is modeled as a log-normal random variable. The efficacy of the developed statistical models is validated by simulating the concentration fields with permeability and porosity of different uncertainty levels. The irregularity in the concentration field bears reasonable visual agreement with that in MicroCT images from experiments. The pressure and velocity fields are represented using polynomial chaos (PC) expansions to enable efficient computation of their statistical properties. The coefficients in the PC expansion are computed using a nonintrusive spectral projection method with the Smolyak sparse quadrature. The developed UQ approach is then used to quantify the uncertainties in the random pressure and velocity fields. A global sensitivity analysis is also performed to assess the contribution of individual KL modes of the log-permeability field to the total variance of the pressure field. It is demonstrated that the developed UQ approach can effectively quantify the flow uncertainties induced by uncertain material properties of the tumor.
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http://dx.doi.org/10.1115/1.4037102DOI Listing
September 2017

MicroCT image based simulation to design heating protocols in magnetic nanoparticle hyperthermia for cancer treatment.

J Therm Biol 2016 Dec 7;62(Pt B):129-137. Epub 2016 Jul 7.

Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, United States. Electronic address:

Objectives: The objective is to design heating protocols to completely damage PC3 tumors after a single magnetic nanoparticle hyperthermia session with minimal collateral thermal damage, based on microCT image generated tumor and mouse models.

Methods: Tumor geometries and volumetric heat generation rate distributions that are generated from microCT scans in our previous study are imported into COMSOL 4.3® multiphysics for heat transfer simulations and heating protocol design using the Arrhenius damage model. Then, parametric studies are performed to evaluate how significantly the infusion rate affects the protocol design and its resulted collateral thermal damage.

Results: The simulated temperature field in the generated tumor geometry and volumetric heat generation rate distribution are reasonable and correlates well with the amount of the total thermal energy deposited into the tumors. The time needed for complete thermal damage is determined to be approximately 12min or 25min if one uses the Arrhenius integral Ω equal to 1 or 4 as the damage threshold, when the infusion rate is 3μL/min. The heating time increases 26% or 91% in the higher infusion rate groups of 4 or 5μL/min, respectively. Collateral thermal damage to the surrounding tissue is also assessed. Although the two larger infusion rate groups can still cause thermal damage to the entire tumor, the collateral thermal damage would have exceeded the design criterion of 5%, while the assessment criterion is acceptable only in the infusion rate group of 3μL/min. Based on the results of this study, we identify an injection strategy and heating protocols to be implemented in future animal experiments to evaluate treatment efficacy for model validation.
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http://dx.doi.org/10.1016/j.jtherbio.2016.06.025DOI Listing
December 2016

Determination of time of death in forensic science via a 3-D whole body heat transfer model.

J Therm Biol 2016 Dec 7;62(Pt B):109-115. Epub 2016 Jul 7.

Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250, United States. Electronic address:

This study is focused on developing a whole body heat transfer model to accurately simulate temperature decay in a body postmortem. The initial steady state temperature field is simulated first and the calculated weighted average body temperature is used to determine the overall heat transfer coefficient at the skin surface, based on thermal equilibrium before death. The transient temperature field postmortem is then simulated using the same boundary condition and the temperature decay curves at several body locations are generated for a time frame of 24h. For practical purposes, curve fitting techniques are used to replace the simulations with a proposed exponential formula with an initial time delay. It is shown that the obtained temperature field in the human body agrees very well with that in the literature. The proposed exponential formula provides an excellent fit with an R value larger than 0.998. For the brain and internal organ sites, the initial time delay varies from 1.6 to 2.9h, when the temperature at the measuring site does not change significantly from its original value. The curve-fitted time constant provides the measurement window after death to be between 8h and 31h if the brain site is used, while it increases 60-95% at the internal organ site. The time constant is larger when the body is exposed to colder air, since a person usually wears more clothing when it is cold outside to keep the body warm and comfortable. We conclude that a one-size-fits-all approach would lead to incorrect estimation of time of death and it is crucial to generate a database of cooling curves taking into consideration all the important factors such as body size and shape, environmental conditions, etc., therefore, leading to accurate determination of time of death.
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http://dx.doi.org/10.1016/j.jtherbio.2016.07.004DOI Listing
December 2016

Identification of infusion strategy for achieving repeatable nanoparticle distribution and quantification of thermal dosage using micro-CT Hounsfield unit in magnetic nanoparticle hyperthermia.

Int J Hyperthermia 2016 12;32(2):132-43. Epub 2016 Jan 12.

a Department of Mechanical Engineering , University of Maryland Baltimore County , Baltimore and.

Objectives: The objective of this study was to identify an injection strategy leading to repeatable nanoparticle deposition patterns in tumours and to quantify volumetric heat generation rate distribution based on micro-CT Hounsfield unit (HU) in magnetic nanoparticle hyperthermia.

Methods: In vivo animal experiments were performed on graft prostatic cancer (PC3) tumours in immunodeficient mice to investigate whether lowering ferrofluid infusion rate improves control of the distribution of magnetic nanoparticles in tumour tissue. Nanoparticle distribution volume obtained from micro-CT scan was used to evaluate spreading of the nanoparticles from the injection site in tumours. Heating experiments were performed to quantify relationships among micro-CT HU values, local nanoparticle concentrations in the tumours, and the ferrofluid-induced volumetric heat generation rate (q(MNH)) when nanoparticles were subject to an alternating magnetic field.

Results: An infusion rate of 3 µL/min was identified to result in the most repeatable nanoparticle distribution in PC3 tumours. Linear relationships have been obtained to first convert micro-CT greyscale values to HU values, then to local nanoparticle concentrations, and finally to nanoparticle-induced q(MNH) values. The total energy deposition rate in tumours was calculated and the observed similarity in total energy deposition rates in all three infusion rate groups suggests improvement in minimising nanoparticle leakage from the tumours. The results of this study demonstrate that micro-CT generated q(MNH) distribution and tumour physical models improve predicting capability of heat transfer simulation for designing reliable treatment protocols using magnetic nanoparticle hyperthermia.
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http://dx.doi.org/10.3109/02656736.2015.1119316DOI Listing
January 2017

MicroCT image-generated tumour geometry and SAR distribution for tumour temperature elevation simulations in magnetic nanoparticle hyperthermia.

Int J Hyperthermia 2013 Dec 30;29(8):730-8. Epub 2013 Sep 30.

Department of Mechanical Engineering, University of Maryland Baltimore County , Baltimore , Maryland .

Objectives: The objective of this study was to develop and test computer algorithms to export micro computed tomography (microCT) images and to generate tumour geometry and specific absorption rate (SAR) distribution for heat transfer simulation in magnetic nanoparticle hyperthermia.

Methods: Computer algorithms were written to analyse and export microCT images of 3D tumours containing magnetic nanoparticles. MATLAB(®) and ProE(®) programs were used to generate a prototype of the tumour geometry. The enhancements in the microCT pixel index number due to presence of nanoparticles in the tumours were first converted into corresponding SAR values. The SAR data were then averaged over three-dimensional clusters of pixels using the SAS(®) program. This greatly decreased the size of the SAR file, while in the meantime it ensured that the amount of total energy deposited in the tumour was conserved. Both the tumour geometry and the SAR file were then imported into the COMSOL(®) software package to simulate temperature elevations in the tumour and their surrounding tissue region during magnetic nanoparticle hyperthermia.

Results: A linear relationship was obtained to relate individual pixel index numbers in the microCT images to the SAR values under a specific magnetic field. The generated prototype of the tumour geometry based on only 30 slices of microCT images resembled the original tumour shape and size. The tumour geometry and the simplified SAR data set were successfully accepted by the COMSOL software for heat transfer simulation. Up to 20 °C temperature elevations from its baseline temperature were found inside the tumours, implying possible thermal damage to the tumour during magnetic nanoparticle hyperthermia.
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http://dx.doi.org/10.3109/02656736.2013.836757DOI Listing
December 2013

Computational simulation of temperature elevations in tumors using Monte Carlo method and comparison to experimental measurements in laser photothermal therapy.

J Biomech Eng 2013 Dec;135(12):121007

Accurate simulation of temperature distribution in tumors induced by gold nanorods during laser photothermal therapy relies on precise measurements of thermal, optical, and physiological properties of the tumor with or without nanorods present. In this study, a computational Monte Carlo simulation algorithm is developed to simulate photon propagation in a spherical tumor to calculate laser energy absorption in the tumor and examine the effects of the absorption (μ(a)) and scattering (μ(s)) coefficients of tumors on the generated heating pattern in the tumor. The laser-generated energy deposition distribution is then incorporated into a 3D finite-element model of prostatic tumors embedded in a mouse body to simulate temperature elevations during laser photothermal therapy using gold nanorods. The simulated temperature elevations are compared with measured temperatures in PC3 prostatic tumors in our previous in vivo experimental studies to extract the optical properties of PC3 tumors containing different concentrations of gold nanorods. It has been shown that the total laser energy deposited in the tumor is dominated by μ(a), while both μ(a) and μ(s) shift the distribution of the energy deposition in the tumor. Three sets of μ(a) and μ(s) are extracted, representing the corresponding optical properties of PC3 tumors containing different concentrations of nanorods to laser irradiance at 808 nm wavelength. With the injection of 0.1 cc of a 250 optical density (OD) nanorod solution, the total laser energy absorption rate is increased by 30% from the case of injecting 0.1 cc of a 50 OD nanorod solution, and by 125% from the control case without nanorod injection. Based on the simulated temperature elevations in the tumor, it is likely that after heating for 15 min, permanent thermal damage occurs in the tumor injected with the 250 OD nanorod solution, while thermal damage to the control tumor and the one injected with the 50 OD nanorod solution may be incomplete.
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http://dx.doi.org/10.1115/1.4025388DOI Listing
December 2013

Numerical study of nanofluid infusion in deformable tissues for hyperthermia cancer treatments.

Med Biol Eng Comput 2011 Nov 14;49(11):1233-40. Epub 2011 Aug 14.

Department of Mechanical Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.

Direct infusion by means of needles is one of the widely used methods for the delivery of nanoparticles in tumors for hyperthermia cancer treatments. During an infusion process, infusion-induced deformation can substantially affect the dispersion of the nanoparticles injected in a biological tissue. In this study, a poroelastic model is developed to investigate fluid transport and flow-induced tissue deformation in a tumor during an infusion process. A surface tracking technique is employed to predict the shape of nanofluid spreading after injection. The model is then used to simulate the formation of backflow and the change of tissue porosity due to the deformation. Specifically, we quantify the influence of the backflow on the spreading shape of the nanofluid and its dependence on injection parameters such as infusion rates, needle diameters, and tumor elastic properties. It is found that backflow is an important factor causing an irregular distribution of the nanofluid injected in a tumor. A higher infusion rate, larger needle diameter, and lower elastic modulus yield a longer backflow length and cause a more irregular spreading shape of the nanofluid. The infusion-induced tissue deformation also leads to a pore swelling and an increase of the porosity in the vicinity of the needle tip and the needle outer surface. It is anticipated that the increased pore size may facilitate the particle penetration in a tumor. To achieve a controlled heat generation, the injection parameters should be selected judiciously with the consideration of tumor sizes, tumor properties, and thresholds at which tumors break under the infusion pressure.
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http://dx.doi.org/10.1007/s11517-011-0819-yDOI Listing
November 2011

Nanoparticle distribution and temperature elevations in prostatic tumours in mice during magnetic nanoparticle hyperthermia.

Int J Hyperthermia 2011 ;27(5):491-502

Department of Mechanical Engineering, University of Maryland Baltimore County , Baltimore, MD 21250, USA.

Among a variety of hyperthermia methods, magnetic nanoparticle hyperthermia is a highly promising approach for its confined heating within the tumour. In this study we perform in vivo animal experiments on implanted prostatic tumours in mice to measure temperature distribution in the tumour during magnetic nanoparticle hyperthermia. Temperature elevations are induced by a commercially available ferrofluid injected via a single injection to the centre of the tumour, when the tumour is subject to an alternating magnetic field. Temperature mapping in the tumours during magnetic nanoparticle hyperthermia has demonstrated the feasibility of elevating tumour temperatures higher than 50°C using only 0.1 cm(3) ferrofluid injected in the tumour under a relatively low magnetic field (3 kA/m). Detailed 3-D nanoparticle concentration distribution is quantified using a high-resolution microCT imaging system. The calculated nanoparticle distribution volume based on the microCT scans is useful to analyse nanoparticle deposition in the tumours. Slower ferrofluid infusion rates result in smaller nanoparticle distribution volumes in the tumours. Nanoparticles are more confined in the vicinity of the injection site with slower infusion rates, causing higher temperature elevations in the tumours. The increase in the nanoparticle distribution volume in the tumour group after the heating from that in the tumour group without heating suggests possible nanoparticle re-distribution in the tumours during the heating.
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http://dx.doi.org/10.3109/02656736.2011.584856DOI Listing
November 2011

Evolution of hsp70 gene expression: a role for changes in AT-richness within promoters.

PLoS One 2011 31;6(5):e20308. Epub 2011 May 31.

Institute of Zoology, Chinese Academy of Sciences, Beijing, China.

In disparate organisms adaptation to thermal stress has been linked to changes in the expression of genes encoding heat-shock proteins (Hsp). The underlying genetics, however, remain elusive. We show here that two AT-rich sequence elements in the promoter region of the hsp70 gene of the fly Liriomyza sativae that are absent in the congeneric species, Liriomyza huidobrensis, have marked cis-regulatory consequences. We studied the cis-regulatory consequences of these elements (called ATRS1 and ATRS2) by measuring the constitutive and heat-shock-induced luciferase luminescence that they drive in cells transfected with constructs carrying them modified, deleted, or intact, in the hsp70 promoter fused to the luciferase gene. The elements affected expression level markedly and in different ways: Deleting ATRS1 augmented both the constitutive and the heat-shock-induced luminescence, suggesting that this element represses transcription. Interestingly, replacing the element with random sequences of the same length and A+T content delivered the wild-type luminescence pattern, proving that the element's high A+T content is crucial for its effects. Deleting ATRS2 decreased luminescence dramatically and almost abolished heat-shock inducibility and so did replacing the element with random sequences matching the element's length and A+T content, suggesting that ATRS2's effects on transcription and heat-shock inducibility involve a common mechanism requiring at least in part the element's specific primary structure. Finally, constitutive and heat-shock luminescence were reduced strongly when two putative binding sites for the Zeste transcription factor identified within ATRS2 were altered through site-directed mutagenesis, and the heat-shock-induced luminescence increased when Zeste was over-expressed, indicating that Zeste participates in the effects mapped to ATRS2 at least in part. AT-rich sequences are common in promoters and our results suggest that they should play important roles in regulatory evolution since they can affect expression markedly and constrain promoter DNA in at least two different ways.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0020308PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3105046PMC
October 2011

Multi-scale study of nanoparticle transport and deposition in tissues during an injection process.

Med Biol Eng Comput 2010 Sep 21;48(9):853-63. Epub 2010 May 21.

Department of Mechanical Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.

In magnetic nanoparticle hyperthermia for cancer treatment, controlling the nanoparticle distribution delivered in tumors is vital for achieving an optimum distribution of temperature elevations that enables a maximum damage of the tumorous cells while minimizing the heating in the surrounding healthy tissues. A multi-scale model is developed in this study to investigate the spatial distribution of nanoparticles in tissues after nanofluid injection into the extracellular space of tissues. The theoretical study consists of a particle trajectory tracking model that considers particle-surface interactions and a macroscale model for the transport of nanoparticles in the carrier solution in a porous structure. Simulations are performed to examine the effects of a variety of injection parameters and particle properties on the particle distribution in tissues. The results show that particle deposition on the cellular structure is the dominant mechanism that leads to a non-uniform particle distribution. The particle penetration depth is sensitive to the injection rate and surface properties of the particles, but relatively insensitive to the injected volume and concentration of the nanofluid.
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http://dx.doi.org/10.1007/s11517-010-0615-0DOI Listing
September 2010

Response of the enzymes to nitrogen applications in cotton fiber (Gossypium hirsutum L.) and their relationships with fiber strength.

Sci China C Life Sci 2009 Nov 24;52(11):1065-72. Epub 2009 Nov 24.

Key Laboratory of Crop Growth Regulation of the Ministry of Agriculture, Nanjing Agricultural University, Nanjing, China.

To investigate the response of key enzymes to nitrogen (N) rates in cotton fiber and its relationship with fiber strength, experiments were conducted in 2005 and 2006 with cotton cultivars in Nanjing. Three N rates 0, 240 and 480 kgN/hm(2), signifying optimum and excessive nitrogen application levels were applied. The activities and the gene expressions of the key enzymes were affected by N, and the characteristics of cellulose accumulation and fiber strength changed as the N rate varied. Beta-1,3-glucanase activity in cotton fiber declined from 9 DPA till boll opening, and the beta-1, 3-glucanase coding gene expression also followed a unimodal curve in 12-24 DPA. In 240 kgN/hm(2) condition, the characteristics of enzyme activity and gene expression manner for sucrose synthase and beta-1,3-glucanase in developing cotton fiber were more favorable for forming a longer and more steady cellulose accumulation process, and for high strength fiber development.
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http://dx.doi.org/10.1007/s11427-009-0147-8DOI Listing
November 2009

An in-vivo experimental study of temperature elevations in animal tissue during magnetic nanoparticle hyperthermia.

Int J Hyperthermia 2008 Nov;24(7):589-601

Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA.

In magnetic nanoparticle hyperthermia in cancer treatment, the local blood perfusion rate and the amount of nanofluid delivered to the target region are important factors determining the temperature distribution in tissue. In this study, we evaluate the effects of these factors on the heating pattern and temperature elevations in the muscle tissue of rat hind limbs induced by intramuscular injections of magnetic nanoparticles during in vivo experiments. Temperature distribution in the vicinity of the injection site is measured inside the rat limb after the nanoparticle hyperthermia. The measured temperature elevations at the injection site are 3.5 degrees +/- 1.8 degrees C and 6.02 degrees +/- 0.8 degrees C above the measured body temperature, when the injection amount is 0.1 cc and 0.2 cc, respectively. The full width of half maximum (FWHM) of the temperature elevation, an index of heat transfer in the radial direction from the injection site is found to be approximately 31 mm for both injection amounts. The temperature measurements, together with the measured blood perfusion rate, ambient air temperature, and limb geometry, are used as inputs into an inverse heat transfer analysis for evaluation of the specific absorption rate (SAR) by the nanoparticles. It has been shown that the nanoparticles are more concentrated in the vicinity of the injection site when the injection amount is bigger. The current in vivo experimental studies have demonstrated the feasibility of elevating the tissue temperature above 43 degrees C under the experimental protocol and equipment used in this study.
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http://dx.doi.org/10.1080/02656730802203377DOI Listing
November 2008