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Papers by nguyen tien

Thau rửa bể nước ăn theo quy trình chuẩn, loại bỏ hoàn toàn chất bẩn mà không gây hư hại đến bể c... more Thau rửa bể nước ăn theo quy trình chuẩn, loại bỏ hoàn toàn chất bẩn mà không gây hư hại đến bể chứa. Dịch vụ thau bể nước uy tín,giá tốt nhất thủ đô.

Lecture Notes in Mathematics, 1989

P ~ 7/zeo~ oz Vector S/ace, 1!/ £cmc.~mw__'87, S~'s L4'M 1 3 9 1 ... Let (~,F,P) b... more P ~ 7/zeo~ oz Vector S/ace, 1!/ £cmc.~mw__'87, S~'s L4'M 1 3 9 1 ... Let (~,F,P) be a probability space and (F n , na I) an incre- ... A sequence (X n , na I) is said to be uniformly ... (I-1) sup { I IXnldP} + O as a + ~ . n~ IXni>a ... (I-2) sup {aP(IXnl > a)} + 0 as a + nEIN

In this report we present some noncommutative weak and strong laws of large numbers. Two case are... more In this report we present some noncommutative weak and strong laws of large numbers. Two case are considered: a von Neumann algebra with a normal faithful state on it and the algebra of measurable operators with normal faithful trace.

Journal of Applied Physics, 2010

We present the theory of an ad hoc mechanism for electron scattering in heavily-doped zinc oxide ... more We present the theory of an ad hoc mechanism for electron scattering in heavily-doped zinc oxide (ZnO) surface quantum wells (SFQWs). We show that the carriers must be extra scattered in the in-plane from roughness-induced fluctuations in the donor density. In combination with the normal scattering from roughness-induced fluctuations in the potential barrier position, this gives rise to an effective roughnessrelated process, referred to as combined surface roughness (CSR) scattering. The CSR scattering is determined by both the roughness and doping profiles. The fluctuating donor density dominates CSR scattering at small angles and is important for large correlation length. The electron mobility in heavilydoped ZnO SFQWs is ruled by CSR scattering. This enables a successful explanation of the mobility data of accumulation layers near the ZnO surface at extremely high electron densities, which has not been explained so far.

Lobachevskii Journal of Mathematics, 2009

In this paper we establish Marcinkiewicz-Zygmund type laws of large numbers for double arrays of ... more In this paper we establish Marcinkiewicz-Zygmund type laws of large numbers for double arrays of random elements in Banach spaces. Our results extend those of Hong and Volodin [6]. ?? Pleiades Publishing, Ltd.

Journal of Applied Physics, 2011

We present the theory of an ad hoc scattering mechanism for carriers confined in a heterostructur... more We present the theory of an ad hoc scattering mechanism for carriers confined in a heterostructure (HS) made of polar materials, such as zinc blends, nitrides, and oxides. We show that the carriers in an actual polar HS must be laterally scattered extra from both piezoelectric and spontaneous polarization charges bound on a rough interface of the system. This is due to roughness-induced fluctuations in the position of interface polarization charges, so referred to as polarization roughness (PR) scattering. The new scattering is combined with the normal surface roughness (SR) scattering, giving rise to an effective roughness-related process, which is referred to as polarization surface roughness (PSR) scattering. The PSR scattering is found to be more important for nearly forward events and at small sheet carrier densities, and it is one of the key mechanisms governing transport in polar HSs. This enables a successful explanation of the mobility data on polar HSs made, e.g., of AlGaN/GaN, which has not been understood so far, starting only from the traditional scattering mechanisms.

Advanced Materials, 2009

Since the first description of their use as potential elements for electronic devices, in 1987, o... more Since the first description of their use as potential elements for electronic devices, in 1987, organic thin-film transistors (OTFTs) have been intensively studied, due to their potentially lower cost, higher performance, and higher compatibility with flexible electronic applications, as compared to conventional silicon technology. Recently, new functions of OTFTs and their integrated circuits have been being considered, in an attempt to take advantage of organic electronic devices in different applications, such as memory, radio-frequency identification (RFID), and sensors. For functional organic devices, organic smart materials with ferroelectric, piezoelectric, and pyroelectric properties can be directly integrated into the OTFT device structure. Good candidates are poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene, P(VDF-TrFE). The piezo-and pyroelectricity of PVDF and P(VDF-TrFE) were studied in depth, and have been successfully applied in many research fields, but the applications of these properties in OTFTs are limited to external sensing modules. On the other hand, there have been both theoretical and experimental reports of memory applications based on the ferroelectricity of P(VDF-TrFE) in OTFTs. High current on-off ratio and fast switching dipoles, which imply a small remnant polarization, are the key aspects in this case. In applications making use of the pyroelectric and piezoelectric properties of P(VDF-TrFE), however, the switching of small remnant polarization should be avoided, and a stable large polarization is required instead. Thus, physical models based on the assumption of small and easy-to-switch remnant polarizations are not appropriate in interpreting the experimental observation in this work, showing a very large remnant polarization, and need to be modified in order to accurately interpret the experimental information.

ACS Nano, 2011

Physically responsive field-effect transistors (physi-FETs) that are sensitive to physical stimul... more Physically responsive field-effect transistors (physi-FETs) that are sensitive to physical stimuli have been studied for decades. The important issue for separating the responses of sensing materials from interference by other subcomponents in a FET transducer under global physical stimuli has not been completely resolved. In addition, challenges remain with regard to the design and employment of smart materials for flexible physi-FETs with a large electro-physical coupling effect. In this article, we propose the direct integration of nanocomposite (NC) gate dielectrics of barium titanate (BT) nanoparticles (NPs) and highly crystalline poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) into flexible organic FETs to achieve a large electro-physical coupling effect. Additionally, a new alternating current biasing method is proposed for precise extraction and quantification of tiny variations in the remnant polarization of NCs caused by mechanical stimuli. An investigation of physi-FETs under static mechanical stimuli revealed the first ever reported giant, positive piezoelectric coefficients of d(33) up to 960 pC/N in the NCs. The large coefficients are presumably due to the significant contributions of the intrinsic positive piezoelectricity of the BT NPs and P(VDF-TrFE) crystallites.

Journal of Hospital Infection, 2005

A cohort study of surgical site infections (SSIs) was conducted in 582 orthopaedic surgical patie... more A cohort study of surgical site infections (SSIs) was conducted in 582 orthopaedic surgical patients at Cho Ray Hospital, a reference hospital in Ho Chi Minh City, Vietnam, in order to determine the incidence and analyse risk factors for SSIs in this population. The SSI incidence rate was 12.5% (73 of 582); 3.6% incisional SSIs, 6.8% deep incisional SSIs and 2.1% organ/space SSIs. The incidence increased from 2% in clean wounds to 44.6% in dirty wounds, or 1.3% in patients with a National Nosocomial Infections Surveillance (NNIS) risk index of 0 to 75% in patients with an NNIS risk ratio of 3. In multi-variate analysis, having a dirty wound [odds ratio (OR) 8.7; 95% confidence intervals (CI) 4.6-16.4], American Society of Anesthesiologists' score O2 (OR 3.9; 95%CI 1.8-8.8), procedures with external fixation (OR 2.9; 95%CI 1.4-5.9), emergency surgery with motor-vehicle-related trauma (OR 2.1; 95%CI 1.2-3.9), or duration of procedure O2 h (OR 2.1; 95%CI 1.1-4.2) were independent risk factors for SSI. Lack of appropriate prophylaxis was of borderline significance (OR 3.2; 95%CI 0.9-11.1, PZ0.06). Among 76 patients with SSIs, 22 patients were discovered during postdischarge follow-up. These late SSIs had age as an additional risk factor (OR 2.8; 95%CI 1.1-7.2). Our data show that SSIs were frequent and differed widely by wound class. The NNIS risk index was predictive of SSI for this population. With a high number of motor vehicle accidents in Vietnam, the majority of orthopaedic operations are trauma related. Emergency surgery for injuries sustained in these accidents, and procedures with external fixation were especially prone to infections.

Infection Control and Hospital Epidemiology, 2006

To determine the pathogens associated with surgical site infections (SSIs) and describe patterns ... more To determine the pathogens associated with surgical site infections (SSIs) and describe patterns of antimicrobial use and resistance in orthopedic and neurosurgical patients in a large university hospital in Vietnam. Prospective cohort study. Cho Ray Hospital, Ho Chi Minh City, Vietnam. All patients who had operations during a 5-week study period. Of 702 surgical patients, 80 (11.4%) developed an SSI. The incidence of SSI among orthopedic patients was 15.2% (48 of 315), and among neurosurgical patients it was 8.3% (32 of 387). Postoperative bacterial cultures of samples from the surgical sites were performed for 55 (68.8%) of the 80 patients with SSI; 68 wound swab specimens and 10 cerebrospinal fluid samples were cultured. Of these 78 cultures, 60 (76.9%) were positive for a pathogen, and 15 (25%) of those 60 cultures yielded multiple pathogens. The 3 most frequently isolated pathogens were Pseudomonas aeruginosa (29.5% of isolates), Staphylococcus aureus (11.5% of isolates), and Escherichia coli (10.3% of isolates). Ninety percent of S. aureus isolates were methicillin resistant, 91% of P. aeruginosa isolates were ceftazidime resistant, and 38% of E. coli isolates were cefotaxime resistant. All but 1 of the 702 patients received antimicrobial therapy after surgery, and the median duration of antimicrobial therapy was 11 days. Commonly used antimicrobials included aminopenicillins and second- and third-generation cephalosporins. Two or more agents were given to 634 (90%) of the patients, and most combination drug regimens (86%) included an aminoglycoside. Our data indicate that the incidence of SSI is high in our study population, that the main pathogens causing SSI are gram-negative bacteria and are often resistant to commonly used antimicrobials, that the use of broad-spectrum antimicrobials after surgery is widespread, and that implementation of interventions aimed at promoting appropriate and evidence-based use of antimicrobials are needed in Vietnam.

British Journal of Clinical Pharmacology, 2002

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1999

The ecology of hepatitis E virus (HEV) transmission in South-East Asia was assessed from a review... more The ecology of hepatitis E virus (HEV) transmission in South-East Asia was assessed from a review of 6 published and 3 unpublished NAMRU-2 reports of hepatitis outbreak investigations, cross-sectional prevalence studies, and hospital-based case-control studies. Findings from Indonesia and Viet Nam show epidemic foci centred in jungle, riverine environments. In contrast, few cases of acute, clinical hepatitis from cities in Indonesia, Viet Nam and Laos could be attributed to HEV. When communities in Indonesia were grouped into areas of low (<40%), medium (40-60%), and high (>60%) prevalence of anti-HEV antibodies, uses of river water for drinking and cooking, personal washing, and human excreta disposal were all significantly associated with high prevalence of infection. Conversely, boiling of river drinking water was negatively associated with higher prevalence (P < 0.01). The protective value ofboiling river water was also shown in sporadic HEV transmission in Indonesia and in epidemic and sporadic spread in Viet Nam. Evidence from Indonesia indicated that the decreased dilution of HEV in river water due to unusually dry weather contributed to risk of epidemic HEV transmission. But river flooding conditions and contamination added to the risk of HEV infection in Viet Nam. These findings attest to a unique combination of ecological and environmental conditions predisposing to epidemic HEV spread in South-East Asia.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2010

A dynamic school-based cohort of 2-15 year-olds was established in Long Xuyen, Viet Nam to provid... more A dynamic school-based cohort of 2-15 year-olds was established in Long Xuyen, Viet Nam to provide epidemiological data for a dengue vaccine efficacy trial. Active surveillance of febrile episodes identified clinically-suspected dengue and acute and convalescent sera were collected. IgG seroconversion between annual seroprevalence surveys identified sub-clinical infections. In 2004, 2190 children were enrolled with 3239, 3146, and 3081 present each year from 2005 to 2007 consecutively. In all, 627 children had a total of 690 clinically-suspected dengue episodes (394 hospitalisations, 296 outpatients) with 284-310 (41.2-45.0%) laboratory-confirmed depending on testing. Dengue serotype 2 was predominant in 2004 and 2005, and serotype 1 in 2006 and 2007. The acute dengue disease incidence rate per 1000 person-years ranged from 16.9 in 2005 to 40.4 in 2007. The average annual incidence of primary dengue infection (IgG seroconversion in previously naïve children) was 11.4% and the symptomatic to asymptomatic primary infection ratio ranged from 1:3-1:6. Study withdrawal rate, a feasibility indicator for conducting efficacy trials, was low: 4.2% per year when excluding children who changed schools. Our 2004-2007 results confirm the high transmission of dengue in children in Long Xuyen and demonstrate the suitability of this study site for a large scale efficacy trial.

New England Journal of Medicine, 2004

Recent outbreaks of avian influenza A (H5N1) in poultry throughout Asia have had major economic a... more Recent outbreaks of avian influenza A (H5N1) in poultry throughout Asia have had major economic and health repercussions. Human infections with this virus were identified in Vietnam in January 2004. We report the clinical features and preliminary epidemiologic findings among 10 patients with confirmed cases of avian influenza A (H5N1) who presented to hospitals in Ho Chi Minh City and Hanoi, Vietnam, in December 2003 and January 2004. In all 10 cases, the diagnosis of influenza A (H5N1) was confirmed by means of viral culture or reverse transcriptase-polymerase chain reaction with primers specific for H5 and N1. None of the 10 patients (mean age, 13.7 years) had preexisting medical conditions. Nine of them had a clear history of direct contact with poultry (median time before onset of illness, three days). All patients presented with fever (temperature, 38.5 to 40.0 degrees C), respiratory symptoms, and clinically significant lymphopenia (median lymphocyte count, 700 per cubic millimeter). The median platelet count was 75,500 per cubic millimeter. Seven patients had diarrhea. In all patients, there were marked abnormalities on chest radiography. There was no definitive evidence of human-to-human transmission. Eight patients died, one patient has recovered, and one is recovering. Influenza A (H5N1) infection, characterized by fever, respiratory symptoms, and lymphopenia, carries a high risk of death. Although in all 10 cases the infection appears to have been acquired directly from infected poultry, the potential exists for genetic reassortment with human influenzaviruses and the evolution of human-to-human transmission. Containment of influenza A (H5N1) in poultry throughout Asia is therefore urgently required.

Journal of Virological Methods, 2007

Reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplifica... more Reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplification method that can be completed within 35 min at 62.5 • C. In the present study, RT-LAMP was used to develop a rapid and sensitive laboratory diagnostic system for the H5N1 highly pathogenic avian influenza (HPAI). The sensitivity of the system was 0.1-0.01 plaque-forming units per reaction for HPAI-H5N1 viruses belonging to the genetically and antigenically distinct clade 1, represented by A/Vietnam/JP1203/2004, and clade 2, represented by A/Indonesia/JP283/2006. This RT-LAMP sensitivity is 10-fold higher than the sensitivity of standard one-step RT-PCR. By using viral RNAs extracted from avian influenza viruses of H1-H15 hemagglutinin (HA) subtypes and human pathogenic respiratory viruses, it was confirmed that the RT-LAMP system amplifies specifically RNA of the H5 subtype virus. The system detected H5-HA genes in throat swabs collected from humans as well as from wild birds. These results suggest that the present RT-LAMP system is a useful diagnostic tool for surveillance of recent outbreaks of the HPAI-H5N1 virus.

Journal of Clinical Virology, 2007

Background: Between January 2005 and April 2006, six patients of influenza A/H5N1 virus infection... more Background: Between January 2005 and April 2006, six patients of influenza A/H5N1 virus infection were reported in Cambodia, all with fatal outcome. Objectives: We describe the virological findings of these six H5N1 patients in association with clinical and epidemiologic findings. Study design: Broncho-alveolar lavage, nasopharyngeal, throat and rectal swabs and sera were cultured for virus isolation and viral load quantified in clinical specimens by real-time RT-PCR. We compared sequences obtained from different body sites within the same patient to detect viral quasi-species. Results: H5N1 virus strains isolated in Cambodia belong to genotype Z, clade 1 viruses. H5N1 viruses were isolated from serum and rectal swab specimens in two patients. The haemagglutinin gene sequences of the virus in different body sites did not differ. Amino acid substitutions known to be associated with a change in virus binding were not observed. Conclusion: The high frequency of virus isolation from serum and faecal swabs highlights that H5N1 is likely to be a disseminated infection in humans and this has implications for antiviral treatment, biosafety in clinical laboratories and on risks for nosocomial and human-to-human transmission. There were no tissue-specific adaptive mutations in the HA gene from viruses isolated from different organs.

Archives of Virology, 2007

A phylogenetic analysis of VP1 and VP4 nucleotide sequences of 52 recent CVA16 strains demonstrat... more A phylogenetic analysis of VP1 and VP4 nucleotide sequences of 52 recent CVA16 strains demonstrated two distinct CVA16 genogroups, A and B, with the prototype strain being the only member of genogroup A. CVA16 G-10, the prototype strain, showed a nucleotide difference of 27.7-30.2% and 19.9-25.2% in VP1 and VP4, respectively, in relation to other CVA16 strains, which formed two separate lineages in genogroup B with nucleotide variation of less than 13.4% and less than 16.3% in VP1 and VP4, respectively. Lineage 1 strains circulating before 2000 were later displaced by lineage 2 strains. Ã Hand, foot, and mouth disease (HFMD) is a common febrile illness of children associated with infections of species A enteroviruses from the genus Enterovirus within the family Picornaviridae. Lesions on the skin and oral mucosa typically characterize the illness, with herpangina also presented in some patients. Several enterovirus serotypes have been associated with this disease, the majority of these being members of human enterovirus A, such as coxsackieviruses (CV) A2, A4, A5, A8, A10, A16 and human enterovirus (HEV) 71 . Of these, CVA16 and HEV71 are the major causative agents associated with HFMD, and co-circulation of both of these serotypes during outbreaks of HFMD

Archives de Pédiatrie, 2004

Mots clés : Méningite bactérienne ; Méningite à Haemophilus influenzae ; Méningite à pneumocoques... more Mots clés : Méningite bactérienne ; Méningite à Haemophilus influenzae ; Méningite à pneumocoques ; Pays en voie de développement