Direct measurement of repulsive and attractive pair potentials using pairs of optical traps.

We present a technique for measuring the interactions between pairs of colloidal particles in two optical traps. This method is particularly suitable for measuring strongly attractive potentials, an otherwise challenging task. The interaction energy is calculated from the distribution of inter-particle separations by accounting for the contribution from the optical traps with arbitrary trap profiles. The method is simple to implement and applicable to different types of pair potentials and optical trapping geometries. We apply the method to measure dipolar pair interactions in experiments with paramagnetic colloids in external magnetic fields. We obtain consistent and accurate results in all regimes, from strongly attractive to repulsive potentials. By means of computer simulations, we demonstrate that the proposed method can be successfully applied to systems with complex pair interactions characterized by multiple attractive and repulsive regimes, which are ubiquitous in soft and biological matter.

Dynamics of a colloidal particle driven by continuous time-delayed feedback.

We perform feedback experiments and simulations in which a colloidal dumbbell particle, acting as a particle on a ring, is followed by a repulsive optical trap controlled by a continuous-time-delayed feedback protocol. The dynamics are described by a persistent random walk similarly to that of an active Brownian particle, with a transition from predominantly diffusive to driven behavior at a critical delay time. We model the dynamics in the short and long delay regimes using stochastic delay differential equations and derive a condition for stable driven motion. We study the stochastic thermodynamic properties of the system, finding that the maximum work done by the trap coincides with a local minimum in the mutual information between the trap and the particle position at the onset of stable driven dynamics.

A novel procedure to obtain nanocrystalline diamond/porous silicon composite by chemical vapor deposition/infiltration processes.

Nanocrystalline diamond (NCD) films were formed on porous silicon (PS) substrate by Chemical Vapor Deposition/Infiltration (CVD/CVI) process using a hot filament reactor. This innovative procedure is determinant to grow a controlled three-dimensional diamond structure with diamond grains formation in the pores, covering uniformly the different growth planes. In this CVI process, a piece of reticulated vitreous carbon (RVC) was used, under de PS substrate, as an additional solid source of hydrocarbon that ensures the production of pertinent carbon growth species directly on PS and into its pores. PS substrates were obtained by anodization etching process of n-type silicon wafer in a hydrofluoric acid (HF) solution containing acetonitrile (CH3CN) which result in an uniform and well controlled porous distribution and size when compared with the usual ethanol solution. Depositions were performed using Ar-H2-CH4 where the methane concentration varied from 0 up to 1.0 vol%, to analyze the influence of RVC use as an additional carbon source on growth mechanism. Scanning Electron Microscopy (SEM) and Field Emission Gun (FEG) were used to investigate PS and NCD film morphology. SEM images of NCD showed faceted nanograins with average size from 5 to 16 nm and uniform surface texture covering all the supports among the pores resulting in an apparent micro honeycomb structure. Raman spectra confirmed the existence of sp2-bonded carbon at the grain boundaries. The spectra showed a peak that may be deconvoluted in two components at 1332 cm(-1) (diamond) and 1345 cm(-1) (D band). Two shoulders at 1150 and 1490 cm(-1) also appear and are assigned to transpolyacetylene (TPA) segments at the grain boundaries of NCD surfaces. In addition, X-ray diffraction analyses of all films presented characteristic diamond diffraction peaks corresponding to (111), (220) and (311).

Stacking-fault based microscopic model for platelets in diamond.

We propose a new model for {001} platelets in diamond based on the formation of a metastable stacking-fault. The core of the defect is a double layer of threefold coordinated sp2 carbon atoms embedded in the sp3 diamond matrix. The properties of the model were determined using ab initio calculations. All significant experimental signatures attributed to the platelets are fully accounted for. The model is also very appealing from the point of view of kinetics, since naturally occurring shearing processes will lead to the formation of the metastable fault.

Distinct patterns of Trypanosoma cruzi infection in Leontopithecus rosalia in distinct Atlantic coastal rainforest fragments in Rio de Janeiro--Brazil.

Previous studies on infection of Trypanosoma cruzi in the Poço das Antas Biological Reserve population of wild free-ranging Leontopithecus rosalia have shown the presence of genotype T. cruzi II, associated in Brazil with human disease. Herein, this study has been extended, the infection being evaluated in L. rosalia of 3 different tamarin populations, inhabiting distinct forest areas located in the same Atlantic Coastal Rainforest. Edentata, Marsupialia, Rodentia and Chiroptera were examined exclusively in the Poço das Antas Biological Reserve. Excluding Chiroptera, T. cruzi infection was found in all orders. Biochemical and molecular characterization demonstrated that golden lion tamarins maintained stable infections by T. cruzi II. The isolates from the other mammals corresponded to T. cruzi I, suggesting independent transmission cycles occurring among the sylvatic mammals inside Poço das Antas Biological Reserve. Significant differences in the infection patterns presented by the 3 populations of wild and captive-born golden lion tamarins were noticed. In Poço das Antas a considerably higher number of positive haemocultures from tamarins with positive serological titres was observed in comparison to those obtained from other areas. The implications for conservation and public health of an active sylvatic cycle in the Atlantic Coastal Rainforest of Rio de Janeiro are discussed.

Depression before and after uterine cervix and breast cancer neoadjuvant chemotherapy.

Depression in cancer patients is common and may affect treatment outcome either directly (by lowering defenses) or indirectly (by lowering compliance). Neoadjuvant chemotherapy for advanced uterine cervix or breast cancer is a strenuous undertaking and may lead to depression and impair patients' willingness to comply with the rest of the treatment (eg, surgery or radiotherapy). We compare Beck Depression Inventory (BDI) scores both before and after neoadjuvant chemotherapy in order to verify if depression influences treatment outcome. We studied 22 advanced uterine cervix and 20 breast cancer patients submitted to three courses of neoadjuvant chemotherapy. We used cisplatin and ifosfamide for cervix, and fluorouracil, adriamycin, and cyclophosphamide for breast cancer. We did not identify significant differences in the number of depressed patients, before and after treatment. Cognitive affective, somatic-performance, and total BDI scores were not significantly different from before to after chemotherapy for both breast and uterine cervix cancer. After treatment, the number of depressive breast cancer patients increased while the number of uterine cervix cancer patients decreased. This trend to depression was found more often in less responsive breast cancer patients than in the more responsive cervix cancer patients. We were not able to link depression to treatment failure or success, but patients who responded to treatment were less depressed at the end of treatment.

Acoustic differences between spontaneous and induced long calls of golden lion tamarins, Leontopithecus rosalia.

Long calls are emitted by several primate taxa and appear to have multiple functions related to spacing mechanisms and reproduction. Yet, in some species the spontaneous rate of emission of these calls is low, and playbacks are used to elicit long calls to augment the sample size of studies. The objective of this study was to compare the acoustic structure of spontaneously emitted and experimentally induced long calls of golden lion tamarins. Results from 6 adult tamarins show that spontaneously emitted long calls differ acoustically from experimentally induced long calls in several frequency measures. Several explanations for these differences are discussed. We conclude that regardless of the underlying mechanisms, playbacks elicit responses that may be different from naturally occurring calls.

Morphometric Characterization of HPV-Related Lesions of Uterine Cervix.

OBJECTIVES: This study addresses three issues related to human papillomavirus (HPV) cervical lesions: identification of HPV in histologic normal tissue, identification of HPV subtypes with risk for cervical cancer, and histologic differences between HPV not associated to cervical intraepithelial neoplasia (CIN1) lesions (condyloma) and HPV associated to CIN1 lesions. MATERIALS AND METHODS: The authors histologically classified 48 cervical biopsy slides into three groups: normal (n = 22), condyloma (n = 20), and CIN1 (n = 6). Morphometric analyses of nuclear and cytoplasmic ratio for area, length, and diameter of 25 cells per case were performed. Histologic reports and in situ hybridization for HPV subtype were compared to morphometric data to assess correlation among them. RESULTS: Using image analysis, the authors correctly classified all cases except two into histologic or in situ hybridization diagnosis. Morphometry helped identify viral changes in cells that appeared histologically normal, HPV subtype at risk in condyloma lesions, and condyloma from those combining HPV lesions and CIN1. CONCLUSIONS: There were enough data supporting morphometric distinction of HPV-related cervical lesions assessed by nuclear and cytoplasmic ratio.

Food transfers in wild and reintroduced golden lion tamarins, Leontopithecus rosalia.

We collected data from wild and reintroduced golden lion tamarins (Leontopithecus rosalia) to describe the behavior of donor and recipient during food transfers, evaluate the effect of supplemental feeding on food transfer behavior, and examine various hypotheses concerning the function of food transfers in primates. Behavioral observations were conducted on 12 groups of tamarins with young (N = 30) between the ages of 1 week and 1 year old. Results show that food transfers involve various behaviors, from steals by recipients to offers by donors; transfers mostly derive from adults and are directed at immature weaned young (between 3 and 9 months old); and that most items transferred were prey or fruits that require skill to process. Eleven percent of food transfers were preceded by an adult vocalization specific to that context, whereas 86% were preceded by conspicuous infant vocalizations and begging behavior. The most common vocalizations were loud and atonal (rasps) and broad banded frequency modulated (trills). Infants born to reintroduced parents vocalized less, whereas reintroduced adults vocalized more before transferring food than their wild counterparts. Reintroduced adults and young received more food transfers (4.4 per hr) than did wild-born adults and young (2.2 per hr). Our findings suggest that food transfer in golden lion tamarins is best understood as provisioning of young that have not fully developed foraging skills to ensure they get the necessary resources for growth and survival.

Higher incidence of Gastrospirillum sp. in swine with gastric ulcer of the pars oesophagea.

Gastric ulcer in swine is characterized by an area of acid-peptic digestion, occurs usually in the pars oesophagea of the stomach, and has unknown etiopathogenesis. The present work was carried out to investigate the prevalence of the newly described spiral-shaped microorganism Gastrospirillum sp. ("Gastrospirillum suis") in stomachs of abattoir pigs with and without gastric ulcer. Stomachs were removed from 32 consecutive pigs presenting apparently normal mucosa and from 32 additional consecutive pigs presenting frank, chronic gastric ulcer of the pars oesophagea. Fragments of antral, oxyntic, cardiac and pars oesophagea regions were taken from each stomach and processed for histology and for identification of Gastrospirillum sp. in tissue sections. The microorganisms were identified mainly in the mucous layer and in gastric foveolas of the antral and oxyntic mucosa. Forty pigs (62.5%) were positive for Gastrospirillum sp.; among them, 27 (67.5%) had gastric ulcer, and 13 (32.5%) had no ulcer. Twenty-four pigs (37.5%) were negative for Gastrospirillum sp.; among them, five (20.8%) presented with gastric ulcer, and 19 (79.2%) had no ulcer. There was a significant difference between pigs with and without gastric ulcer in regard to the presence of Gastrospirillum sp. (P < 0.01). The spiral-shaped microorganism Gastrospirillum sp. that inhabits the stomach of pigs should be considered a possible factor connected with the etiopathogenesis of swine gastric ulcer.