Interparticle Interactions and Self-Assembly of Functionalized Nanodiamonds

Although unpassivated detonation nanodiamonds are known to form tightly bound (and sometimes ordered) superstructures, in most high performance applications the surface are deliberately functionalized, and this can profoundly alter the aggregation behavior. In the present study, we model the aggregation of functionalized nanodiamonds and show that functionalization greatly reduces the Coulombic interactions characteristic of unsaturated particles. Our results provide new insights into the interactions of functionalized nanoparticles.

Nanodiamond for hydrogen storage: temperature-dependent hydrogenation and charge-induced dehydrogenation

Carbon-based hydrogen storage materials are one of hottest research topics in materials science. Although the majority of studies focus on highly porous loosely bound systems, these systems have various limitations including use at elevated temperature. Here we propose, based on computer simulations, that diamond nanoparticles may provide a new promising high temperature candidate with a moderate storage capacity, but good potential for recyclability. The hydrogenation of nanodiamonds is found to be easily achieved, in agreement with experiments, though we find the stability of hydrogenation is dependent on the morphology of nanodiamonds and surrounding environment. Hydrogenation is thermodynamically favourable even at high temperature in pure hydrogen, ammonia, and methane gas reservoirs, whereas water vapour can help to reduce the energy barrier for desorption. The greatest challenge in using this material is the breaking of the strong covalent C-H bonds, and we have identified that the spontaneous release of atomic hydrogen may be achieved through charging of hydrogenated nanodiamonds. If the degree of induced charge is properly controlled, the integrity of the host nanodiamond is maintained, which indicates that an efficient and recyclable approach for hydrogen release may be possible.

Effect of donor cell type on nuclear remodelling in rabbit somatic cell nuclear transfer embryos

Cloned rabbits have been produced for many years by somatic cell nuclear transfer (SCNT). The efficiency of cloning by SCNT, however, has remained extremely low. Most cloned embryos degenerate in utero, and the few that develop to term show a high incidence of post-natal death and abnormalities. The cell type used for donor nuclei is an important factor in nuclear transfer (NT). As reported previously, NT embryos reconstructed with fresh cumulus cells (CC-embryos) have better developmental potential than those reconstructed with foetal fibroblasts (FF-embryos) in vivo and in vitro. The reason for this disparity in developmental capacity is still unknown. In this study, we compared active demethylation levels and morphological changes between the nuclei of CC-embryos and FF-embryos shortly after activation. Anti-5-methylcytosine immunofluorescence of in vivo-fertilized and cloned rabbit embryos revealed that there was no detectable active demethylation in rabbit zygotes or NT-embryos derived from either fibroblasts or CC. In the process of nuclear remodelling, however, the proportion of nuclei with abnormal appearance in FF-embryos was significantly higher than that in CC-embryos during the first cell cycle. Our study demonstrates that the nuclear remodelling abnormality of cloned rabbit embryos may be one important factor for the disparity in developmental success between CC-embryos and FF-embryos.

Obesity, alexithymia and psychopathology: a case-control study

OBJECTIVE

The relationship between psychopathology and alexithymia in obese patients is uncertain. The present study was performed to evaluate this relationship in a clinical sample of patients attending a centre for the diagnosis and treatment of obesity compared to a matched sample of non-obese subjects.

METHODS

293 consecutive obese patients (48 males, 245 females, mean age 45, 41±13.55 yrs; mean BMI 35.60±6.20) were compared with a control group made of 293 non-obese subjects (48 males, 245 females, mean age 45, 66±13.86 yrs; mean BMI 21.8±2.06); all subjects were interviewed by means of SCID I and SCID II together with several self-evaluation instruments including the TAS-20 (Toronto Alexithymia Scale) and SCL-90 (Symptom Check List, Revised).

RESULTS

Alexithymia was significantly more frequent among obese patients compared to "normal" controls (12.9% vs 6.9%, p=0.010); moreover obese patients achieved significantly higher mean scores on subscales 1 and 2 and on overall scale of the Toronto Alexithymia Scale; comorbidity with axis I/II disorders, in particular Binge Eating Disorder, was associated with a significantly higher frequency of alexithymic traits and higher scores at TAS.

CONCLUSIONS

Alexithymia and psychopathology are strongly correlated among obese patients seeking treatment. Routine evaluation of personality traits and comorbid psychopathology may be relevant in treatment of obesity.

Half metallicity in BC2)N nanoribbons: stability, electronic structures, and magnetism

Nanoribbons are suggested to be among the most promising candidates being considered as building blocks in future electronics. In this study, we use density functional calculations to examine the structures and electronic properties of BC(2)N nanoribbons with bare zigzag-shaped edges (zz-BC(2)NNRs). Four different types of atomistic edge configurations are considered, including ribbons terminated with two C edges, B and N edges, B an C edges, and C and N edges. We find the existence of half-metallicity in the ground state of the zz-BC(2)NNRs with two bare C edges and with bare C and N edges. The other two configurations of the zz-BC(2)NNRs can be either semiconducting or metallic, depending on the specific configuration. We also find that the stability of the zz-BC(2)NNRs are largely dependent on ribbon width. The zz-BC(2)NNRs become energetically more stable when the nanoribbon width exceeds 3.3 nm. It is interesting to find that half-metallic zz-BC(2)NNRs with a width of 0.7 nm are thermodynamically more stable than either metallic or semiconducting counterparts. Therefore, the possibility of synthesizing half-metallic zz-BC(2)NNRs exists.

Modeling the thermostability of surface functionalisation by oxygen, hydroxyl, and water on nanodiamonds

Understanding nanodiamond functionalisation is of great importance for biological and medical applications. Here we examine the stabilities of oxygen, hydroxyl, and water functionalisation of the nanodiamonds using the self-consistent charge density functional tight-binding simulations. We find that the oxygen and hydroxyl termination are thermodynamically favourable and form strong C–O covalent bonds on the nanodiamond surface in an O2 and H2 gas reservoir, which confirms previous experiments. Yet, the thermodynamic stabilities of oxygen and hydroxyl functionalisation decrease dramatically in a water vapour reservoir. In contrast, H2O molecules are found to be physically adsorbed on the nanodiamond surface, and forced chemical adsorption results in decomposition of H2O. Moreover, the functionalisation efficiency is found to be facet dependent. The oxygen functionalisation prefers the {100} facets as opposed to alternative facets in an O2 and H2 gas reservoir. The hydroxyl functionalisation favors the {111} surfaces in an O2 and H2 reservoir and the {100} facets in a water vapour reservoir, respectively. This facet selectivity is found to be largely dependent upon the environmental temperature, chemical reservoir, and morphology of the nanodiamonds.

Structural, electronic and magnetic properties of ultra-narrow NbSe2 nanoribbons

Structural, electronic and magnetic properties of ultra-narrow NbSe2 nanoribbons with different chirality and edge structures are studied by using density functional theory calculations. Armchair-like NbSe2 nanoribbons exhibit nonmagnetic and metal behavior. Zigzag-like NbSe2 nanoribbons always have ferromagnetic ground states with electronic types ranging from semiconductor, metal, even to half-metal. And stability estimation indicates that the zigzag-like NbSe2 nanoribbons with 50% Se passivation at Nb edges are the most energetically stable. All these findings suggest potential applications of NbSe2 nanoribbons in spintronic devices.

Relapse of amoebic infection 10 years after the infection

A 52-year-old man with schizophrenia, who had a history of amoebic liver abscess treated with combination antimicrobial agents, presented 10 years later with severe rectal bleeding. Diagnosis of amoebic colitis was confirmed by histological examination of endoscopic biopsy. Doctors treating patients with amoebic infection should be aware of the risk of eradication failure. Post-treatment stool testing, preferably by antigen testing or polymerase chain reaction, should be performed after antimicrobial treatment.

Hepatocarcinogenesis of regenerative and dysplastic nodules in Chinese patients

OBJECTIVES

To determine the development rate of hepatocellular carcinoma and survival of patients diagnosed to have regenerative, and low-grade and high-grade dysplastic liver nodules.

DESIGN

Retrospective descriptive study.

SETTING

Acute public hospital, Hong Kong.

PATIENTS

Patients with non-malignant liver nodules confirmed by imaging-guided liver biopsy between January 1997 and December 2008.

MAIN OUTCOME MEASURES

Rates of hepatocellular carcinoma development and survival.

RESULTS

A total of 147 patients with non-malignant liver nodules were followed up over a median duration of 29 months. The initial histological diagnosis included regenerative nodules (n=74), low-grade dysplastic nodules (n=34), and high-grade dysplastic nodules (n=39). The respective cumulative hepatocellular carcinoma development rate during the first, second, third, and fourth year were 3%, 5%, 9% and 12% for simple regenerative nodules, 29%, 35%, 38% and 44% for low-grade dysplastic nodules, and 38%, 41%, 51% and 51% for high-grade dysplastic nodules. The hepatocellular carcinoma development rate was highest in those with high-grade dysplastic nodules. Multivariate analysis showed that histological dysplastic changes were associated with increased alpha-fetoprotein levels and advanced age, which were both independent predictors of hepatocellular carcinoma development. Histological dysplastic changes, male sex, advanced age, prolonged prothrombin time, and ultrasound appearances were independent predictors of mortality.

CONCLUSION

The presence of dysplastic change in liver nodules increased the risk of hepatocellular carcinoma development and death.

Abstract P1-01-19: Comparison of Ultrasound-Guided Fine Needles Aspiration Cytology and Ultrasound Guided Core Biopsy in Pre-Operative Axillary Staging for Early Breast Cancer

Introduction: Pre-operative axillary staging is now widely accepted as a prerequisite in surgical management of the axilla for patients newly diagnosed with early breast cancer. For those patients having breast tumour excision who are found to have nodal involvement, axillary clearance can be performed at the same time without prior sentinel node biopsy. Ultrasound (US) alone has low sensitivity, but can be used to direct needle biopsy. We assessed and compared the sensitivity and specificity of US-guided core biopsies (USCB) and US-guided fine needle cytology (USFNAC) used in our unit.

Patients and methods: A retrospective and prospective data collection was performed between November 2007 and May 2010 on all newly diagnosed breast cancer patients in our unit since the introduction of routine pre-operative axillary US. Patients whose nodes looked benign or normal on US were offered sentinel node biopsy (SNB). Patients found to have suspicious nodes were offered USFNAC or USCB, according to the individual preference of the radiologists. Patients with positive cytology or histology underwent axillary node clearances (ANC), those with benign cytology or histology were offered SNB. The final histology results were reviewed and correlated to their pre-operative histology or cytology.

Results: Of 559 Axillary ultrasound scans performed in our department between November 2007 and May 2010, 229 patients had pre-operative US scans of the axilla for newly diagnosed, clinically node-negative breast cancer. Of these 46 had USFNAC, 44 had USCB and 139 had normal/benign US. The USFNAC and USCB groups had similar proportions of positive results on postoperative histology, namely 70% and 79% respectively, allowing direct comparisons to be made. Of the 46 USFNAC patients, 17 (37%) had positive cytology (all confirmed by axillary clearance final histology). The 29 USFNAC patients with negative cytology had 15 (52%) with positive histology on sentinel node biopsy. The sensitivity of USFNAC was 53% and the specificity 100%. Of the 44 USCB patients, 26 (59%) were positive (all confirmed by axillary clearance final histology). Of the 18 USCB-negative patients, 7 (39%) were found to be positive on axillary clearance. The sensitivity of USCB was 79% and the specificity 100%. Of the 139 patients with normal US, 42 (30%) were found to be positive on sentinel node biopsies. For US alone, sensitivity was 61% and specificity was 80%.

Conclusion: US staging of the axilla is superior to clinical staging. However, there is still a high incidence of false negative results, making US a crude way of assessing the axilla and confirming the necessity for sentinel node biopsy in US-negative axillae. For patients with axillae that are indeterminate on US, our data supports routine use of ultrasound core biopsy (USCB) over Ultrasound fine needle aspiration cytology (USFNAC) for preoperative staging of the axilla, where technically feasible.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-01-19.

Adsorption of nucleic acid bases and amino acids on single-walled carbon and boron nitride nanotubes: a first-principles study

We study the adsorptions of nucleic acid bases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) and four amino acids phenylalanine, tyrosine, tryptophan, alanine on the single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (SWBNNTs) by using density functional theory. We find that the aromatic content plays a critical role in the adsorption. The adsorptions of nucleic acid bases and amino acids on the (7, 7) SWBNNT are stronger than those on the (7, 7) SWCNT. Oxidative treatment of SWCNTs favors the adsorption of biomolecules on nanotubes.

Study on the dispersion of charged single-wall carbon nanotube bundles by first principles calculation

We have investigated the dispersion of charged single-wall carbon nanotube bundles by using density functional theory. We obtained the variation of equilibrium spacing between tubes as a function of charge density for the (4, 4) and (7, 0) tubes with different charge signs and the minimum charge density to cause separation. We also calculated the cohesive energies between two charged tubes as a function of interwall spacing and found that extra energy supply can promote separation of nanotube bundle. Our results are in good agreement with the experimental values.