This article provides a comprehensive review of current research activities that concentrate on one‐dimensional (1D) nanostructures—wires, rods, belts, and tubes—whose lateral dimensions fall ...anywhere in the range of 1 to 100 nm. We devote the most attention to 1D nanostructures that have been synthesized in relatively copious quantities using chemical methods. We begin this article with an overview of synthetic strategies that have been exploited to achieve 1D growth. We then elaborate on these approaches in the following four sections: i) anisotropic growth dictated by the crystallographic structure of a solid material; ii) anisotropic growth confined and directed by various templates; iii) anisotropic growth kinetically controlled by supersaturation or through the use of an appropriate capping reagent; and iv) new concepts not yet fully demonstrated, but with long‐term potential in generating 1D nanostructures. Following is a discussion of techniques for generating various types of important heterostructured nanowires. By the end of this article, we highlight a range of unique properties (e.g., thermal, mechanical, electronic, optoelectronic, optical, nonlinear optical, and field emission) associated with different types of 1D nanostructures. We also briefly discuss a number of methods potentially useful for assembling 1D nanostructures into functional devices based on crossbar junctions, and complex architectures such as 2D and 3D periodic lattices. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials might be directed.
Current research activities concentrating on one‐dimensional (1D) nanostructures—wires, rods, belts, and tubes—are comprehensively reviewed. Chemical methods of synthesis are introduced and a range of growth mechanisms discussed in terms of shape control. The generation of heterostructured nanowires is detailed, as is the range of unique properties of 1D nanostructures. The assembly of 1D nanostructures into functional devices is also mentioned. The article concludes with perspectives on future research and related issues.
Tellurium nanotubes with well‐controlled structures (see Figure) are obtained via concentration depletion at the surfaces of seeds. The lengths of these inorganic nanotubes can be varied by adjusting ...the growth time (see cover), and the outer diameters of the tubes can be controlled by changing the initial concentration of the precursor acid.
We have recently developed a simple and versatile route to the large‐scale synthesis of metal nanostructures with well‐defined hollow interiors. The key step of this process involves a replacement ...reaction between the surface of a nanoscale template and the solution of an appropriate salt precursor. The capability and feasibility of this method have been demonstrated by preparing hollow nanostructures of gold with a range of different morphologies (e.g., triangular rings, prism‐shaped boxes, cubic boxes, spherical capsules, and tubes). In addition to gold, this method also worked well for other metals such as platinum and palladium (see Figure for an SEM image of Pd nanotubes). These metal nanostructures with hollow interiors are useful as fillers for generation of ultralight composites; they are also interesting for new types of applications that include use as components for highly sensitive colorimetric sensors and as effective, recoverable catalysts.
A simple and versatile route has been developed for the large‐scale synthesis of metal nanostructures with well‐defined hollow interiors. The capability of the method has been demonstrated by preparing a range of hollow nanostructures of gold (e.g., triangular rings, prism‐shaped or cubic boxes, spherical capsules, and tubes), and it also works well for other metals such as Pt and Pd (see Figure for an SEM image of Pd nanotubes).
This article describes a soft, solution‐phase approach to the large‐scale synthesis of uniform nanowires of trigonal selenium (t‐Se) with lateral dimensions controllable in the range of ∼10 to ∼800 ...nm, and lengths up to hundreds of micrometers. These highly anisotropic, one‐dimensional (1D) nanostructures were directly nucleated and grown from aqueous solutions without the help of any physical templates, such as channel‐like structures etched in porous materials, or scaffolds assembled from surfactants or block‐copolymers. The 1D morphology of the product was solely determined by the linear characteristics of the building blocks—i.e., the extended, helical chains of atoms contained in the crystalline lattice of t‐Se. A blue shift was observed for the bandgap and interchain transition of these nanowires when their diameters were reduced from ∼32 to ∼10 nm. The photoconductivity of individual nanowires has also been measured using the four‐probe method, and an increase by ∼150 times was found when the sample was taken from the dark and exposed with ∼3 μW μm–2 tungsten light. Since no exotic seeds were involved in this synthetic process, every nanowire (including both ends) should be made entirely of pure selenium, crystallized in the trigonal phase. We believe the protocol described here can be scaled up for the high‐volume production of t‐Se nanowires that can subsequently serve as the physical or chemical templates to generate 1D nanostructures of various kinds of functional materials. The synthetic strategy itself, may also be extendable to other systems containing chain‐like building blocks. The single crystallinity and absence of kinks and other related defects in these nanowires should make them particularly useful in fabricating nanoscale electronic, optical, or mechanical nanodevices.
Highly pure trigonal selenium nanowires (see Figure) have been obtained by soft solution processing. Spectral measurements suggest a blue‐shift in the bandgap and exciton peaks for these t‐Se nanowires when their mean diameter is decreased. The absence of kinks and related defects in these selenium nanowires makes this new class of 1D nanostructures particularly useful in the fabrication of electronic, optical, or electromechanical devices.
Single crystalline selenium nanowires have been successfully synthesized using a sonochemical process. These uniform nanowires can be grown in solutions or on substrates at room temperature with ...yields approaching 100 %. The nanowires could also be directed to grow into self‐connecting networks (see Figure), and to form electrically continuous connections between two electrodes.
The purpose of this study was to compare self-reported symptoms for exercise-induced asthma (EIA) to postexercise challenge pulmonary function test results in elite athletes.
Elite athletes (N = 158; ...83 men and 75 women; age: 22 +/- 4.4 yr) performed pre- and post-exercise spirometry and were grouped according to postexercise pulmonary function decrements (PFT-positive, PFT-borderline, and PFT-normal for EIA). Before the sport/environment specific exercise challenge, subjects completed an EIA symptoms-specific questionnaire.
Resting FEV1 values were above predicted values (114--121%) and not different between groups. Twenty-six percent of the study population demonstrated >10% postexercise drop in FEV1 and 29% reported two or more symptoms. However, the proportion of PFT-positive and PFT-normal athletes reporting two or more symptoms was not different (39% vs. 41%). Postrace cough was the most reported symptom, reported significantly more frequently for PFT-positive athletes (P < 0.05). Sensitivity/specificity analysis demonstrated a lack of effectiveness of self-reported symptoms to identify PFT-positive or exclude PFT-normal athletes. Postexercise lower limit reference ranges (MN-2SDs) were determined from normal athletes for FEV1, FEF25--75% and PEF to be -7%, -12.5%, and -18%, respectively.
Although questionnaires provide reasonable estimates of EIA prevalence among elite cold-weather athletes, the use of self-reported symptoms for EIA diagnosis in this population will likely yield high frequencies of both false positive and false negative results. Diagnosis should include spirometry using an exercise/environment specific challenge in combination with the athlete's history of asthma symptoms.
Abstract Purpose To survey the prevalence of body art and incidence of medical complications among university students comparing results in 2001 and 2006. Methods Students reported body piercings and ...tattoos and occurrence of medical complications. Results Prevalence of body piercing was 51% and tattooing 22%. Piercing medical complication incidence was 19%. No tattooing medical complications occurred. Conclusions Body art is prevalent among undergraduate university students, with prevalence essentially unchanged during two consecutive 5-year samples. Medical complications occur frequently among those with piercings.
Three perioperative factors impair host defence against recurrence during cancer surgery: the surgical stress response, use of volatile anaesthetic, and opioids for analgesia. All factors are ...ameliorated by regional anaesthesia-analgesia. We tested the primary hypothesis that breast cancer recurrence after potentially curative surgery is lower with regional anaesthesia-analgesia using paravertebral blocks and the anaesthetic propofol than with general anaesthesia with the volatile anaesthetic sevoflurane and opioid analgesia. A second hypothesis was that regional anaesthesia-analgesia reduces persistent incisional pain.
We did a randomised controlled trial at 13 hospitals in Argentina, Austria, China, Germany, Ireland, New Zealand, Singapore, and the USA. Women (age <85 years) having potentially curative primary breast cancer resections were randomised by computer to either regional anaesthesia-analgesia (paravertebral blocks and propofol) or general anaesthesia (sevoflurane) and opioid analgesia. The primary outcome was local or metastatic breast cancer recurrence. The secondary outcome was incisional pain at 6 months and 12 months. Primary analyses were done under intention-to-treat principles. This trial is registered with ClinicalTrials.gov, NCT00418457. The study was stopped after a preplanned futility boundary was crossed.
Between Jan 30, 2007, and Jan 18, 2018, 2132 women were enrolled to the study, of whom 24 were excluded before surgery. 1043 were assigned to regional anaesthesia-analgesia and 1065 were allocated to general anaesthesia. Baseline characteristics were well balanced between study groups. Median follow-up was 36 (IQR 24–49) months. Among women assigned regional anaesthesia-analgesia, 102 (10%) recurrences were reported, compared with 111 (10%) recurrences among those allocated general anaesthesia (hazard ratio 0·97, 95% CI 0·74–1·28; p=0·84). Incisional pain was reported by 442 (52%) of 856 patients assigned to regional anaesthesia-analgesia and 456 (52%) of 872 patients allocated to general anaesthesia at 6 months, and by 239 (28%) of 854 patients and 232 (27%) of 852 patients, respectively, at 12 months (overall interim-adjusted odds ratio 1·00, 95% CI 0·85–1·17; p=0·99). Neuropathic breast pain did not differ by anaesthetic technique and was reported by 87 (10%) of 859 patients assigned to regional anaesthesia-analgesia and 89 (10%) of 870 patients allocated to general anaesthesia at 6 months, and by 57 (7%) of 857 patients and 57 (7%) of 854 patients, respectively, at 12 months.
In our study population, regional anaesthesia-analgesia (paravertebral block and propofol) did not reduce breast cancer recurrence after potentially curative surgery compared with volatile anaesthesia (sevoflurane) and opioids. The frequency and severity of persistent incisional breast pain was unaffected by anaesthetic technique. Clinicians can use regional or general anaesthesia with respect to breast cancer recurrence and persistent incisional pain.
Sisk Healthcare Foundation (Ireland), Eccles Breast Cancer Research Fund, British Journal of Anaesthesia International, College of Anaesthetists of Ireland, Peking Union Medical College Hospital, Science Fund for Junior Faculty 2016, Central Bank of Austria, and National Healthcare Group.
To survey the prevalence of body art (body piercing and tattooing) in university undergraduate students and to determine the incidence of medical complications from these procedures.
Between February ...and May 2001, students were offered the opportunity to complete an anonymous, voluntary survey at the beginning of class or organizational meetings. The survey instrument requested information concerning body piercing and tattooing (current or removed) by body site, age, sex, height, weight, body mass index, undergraduate class, athletic status, and the occurrence of medical complications.
Four hundred fifty-four (94.4%) of 481 students completed the survey (14.7% of total campus enrollment). The prevalence of body piercing was 51%, and that of tattooing was 23%. The χ
2 analysis showed female students were more likely to be pierced than males (
P=.002); there was no significant difference in the prevalence of tattooing by sex. Male athletes were more likely to be tattooed than male nonathletes (
P=.02). No relationships were shown between piercing/tattooing and age or measures of body somatotype. The incidence of medical complications of piercing was 17%, and these complications included bleeding, tissue trauma, and bacterial infections. Pierced navels were particularly prone to infection. There were no reported medical complications from tattooing. Eighteen percent of piercings (58/315) and 4% of tattoos (6/149) had been removed.
Body art is prevalent among undergraduate university students, and there is a significant incidence of medical complications among students with piercing. Male athletes were significantly more likely to be tattooed than male nonathletes.
Se@CdSe nanocables and CdSe nanotubes with diameters of around 50 nm (see Figure) can be directly synthesized via a template‐ engaged approach in aqueous solution. The walls of these nanotubes are ...composed of CdSe nanoparticles 5–10 nm in size. It is believed this approach can be potentially extended to process many other chalcogenides into tubular nanostructures.
