Autonomous atmospheric water seeping MOF matrix.

The atmosphere contains an abundance of fresh water, but this resource has yet to be harvested efficiently. To date, passive atmospheric water sorbents have required a desorption step that relies on steady solar irradiation. Since the availability and intensity of solar radiation vary, these limit on-demand desorption and hence the amount of harvestable water. Here, we report a polymer-metal-organic framework that provides simultaneous and uninterrupted sorption and release of atmospheric water. The adaptable nature of the hydro-active polymer, and its hybridization with a metal-organic framework, enables enhanced sorption kinetics, water uptake, and spontaneous water oozing. We demonstrate continuous water delivery for 1440 hours, producing 6 g of fresh water per gram of sorbent at 90% relative humidity (RH) per day without active condensation. This leads to a total liquid delivery efficiency of 95% and an autonomous liquid delivery efficiency of 71%, the record among reported atmospheric water harvesters.

The quantum-confined Stark effect in layered hybrid perovskites mediated by orientational polarizability of confined dipoles.

The quantum-confined Stark effect (QCSE) is an established optical modulation mechanism, yet top-performing modulators harnessing it rely on costly fabrication processes. Here, we present large modulation amplitudes for solution-processed layered hybrid perovskites and a modulation mechanism related to the orientational polarizability of dipolar cations confined within these self-assembled quantum wells. We report an anomalous (blue-shifting) QCSE for layers that contain methylammonium cations, in contrast with cesium-containing layers that show normal (red-shifting) behavior. We attribute the blue-shifts to an extraordinary diminution in the exciton binding energy that arises from an augmented separation of the electron and hole wavefunctions caused by the orientational response of the dipolar cations. The absorption coefficient changes, realized by either the red- or blue-shifts, are the strongest among solution-processed materials at room temperature and are comparable to those exhibited in the highest-performing epitaxial compound semiconductor heterostructures.

Effect of disorder on transport properties in a tight-binding model for lead halide perovskites.

The hybrid organic-inorganic lead halide perovskite materials have emerged as remarkable materials for photovoltaic applications. Their strengths include good electric transport properties in spite of the disorder inherent in them. Motivated by this observation, we analyze the effects of disorder on the energy eigenstates of a tight-binding model of these materials. In particular, we analyze the spatial extension of the energy eigenstates, which is quantified by the inverse participation ratio. This parameter exhibits a tendency, and possibly a phase transition, to localization as the on-site energy disorder strength is increased. However, we argue that the disorder in the lead halide perovskites corresponds to a point in the regime of highly delocalized states. Our results also suggest that the electronic states of mixed-halide materials tend to be more localized than those of pure materials, which suggests a weaker tendency to form extended bonding states in the mixed-halide materials and is therefore not favourable for halide mixing.

Power-free, digital and programmable dispensing of picoliter droplets using a Digit Chip.

There is a growing need for power-free methods to manipulate small volumes of liquids and thereby enable use of diagnostic assays in resource-limited settings. Most existing self-powered devices provide analog manipulation of fluids using paper, capillary or pressure-driven pumps. These strategies are well-suited to manipulating larger micro- and milliliter-scale volumes at constant flow rates; however, they fail to enable the manipulation of nanoliter and picoliter volumes required in assays using droplets, capillary sampling (e.g. finger prick), or expensive reagents. Here we report a device, termed the Digit Chip, that provides programmable and power-free digital manipulation of sub-nanoliter volumes. The device consists of a user-friendly button interface and a series of chambers connected by capillary valves that serve as digitization elements. Via a button press, the user dispenses and actuates ultra-small, quantitatively-programmed volumes. The device geometry is optimized using design models and experiments and precisely dispenses volumes as low as 21 pL with 97% accuracy. The volume dispensed can be tuned in 10 discrete steps across one order-of-magnitude with 98% accuracy. As a proof-of-principle that nanoliter-scale reagents can be precisely actuated and combined on-chip, we deploy the device to construct a precise concentration gradient with 10 discrete concentrations. Additionally, we apply this device alongside an inexpensive smartphone-based fluorescence imaging platform to perform a titration of E. coli with ampicillin. We observe the onset of bacterial death at a concentration of 5 µg mL-1, increasing to a maximum at 50 µg mL-1. These results establish the utility of the Digit Chip for diagnostic applications in low-resource environments.

Broadband Epsilon-near-Zero Reflectors Enhance the Quantum Efficiency of Thin Solar Cells at Visible and Infrared Wavelengths.

The engineering of broadband absorbers to harvest white light in thin-film semiconductors is a major challenge in developing renewable materials for energy harvesting. Many solution-processed materials with high manufacturability and low cost, such as semiconductor quantum dots, require the use of film structures with thicknesses on the order of 1 µm to absorb incoming photons completely. The electron transport lengths in these media, however, are 1 order of magnitude smaller than this length, hampering further progress with this platform. Herein, we show that, by engineering suitably disordered nanoplasmonic structures, we have created a new class of dispersionless epsilon-near-zero composite materials that efficiently harness white light. Our nanostructures localize light in the dielectric region outside the epsilon-near-zero material with characteristic lengths of 10-100 nm, resulting in an efficient system for harvesting broadband light when a thin absorptive film is deposited on top of the structure. By using a combination of theory and experiments, we demonstrate that ultrathin layers down to 50 nm of colloidal quantum dots deposited atop the epsilon-near-zero material show an increase in broadband absorption ranging from 200% to 500% compared to a planar structure of the same colloidal quantum-dot-absorber average thickness. When the epsilon-near-zero nanostructures were used in an energy-harvesting module, we observed a spectrally averaged 170% broadband increase in the external quantum efficiency of the device, measured at wavelengths between 400 and 1200 nm. Atomic force microscopy and photoluminescence excitation measurements demonstrate that the properties of these epsilon-near-zero structures apply to general metals and could be used to enhance the near-field absorption of semiconductor structures more widely. We have developed an inexpensive electrochemical deposition process that enables scaled-up production of this nanomaterial for large-scale energy-harvesting applications.

Atomistic model of fluorescence intermittency of colloidal quantum dots.

Optoelectronic applications of colloidal quantum dots demand a high emission efficiency, stability in time, and narrow spectral bandwidth. Electronic trap states interfere with the above properties but understanding of their origin remains lacking, inhibiting the development of robust passivation techniques. Here we show that surface vacancies improve the fluorescence yield compared to vacancy-free surfaces, while dynamic vacancy aggregation can temporarily turn fluorescence off. We find that infilling with foreign cations can stabilize the vacancies, inhibiting intermittency and improving quantum yield, providing an explanation of recent experimental observations.

Dynamic Trap Formation and Elimination in Colloidal Quantum Dots.

Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping.

The human relevant potency threshold: reducing uncertainty by human calibration of cumulative risk assessments.

The 2008 National Research Council report "Phthalates and Cumulative Risk Assessment: Tasks Ahead," rejected the underlying premises of TEQ-like approaches - e.g., chemicals are true congeners; are metabolized and detoxified similarly; produce the same biological effects by the same mode of action; exhibit parallel dose response curves - instead asserting that cumulative risk assessment should apply dose addition (DA) to all chemicals that produce "common adverse outcomes" (CAOS). Published mixtures data and a human health risk assessment for phthalates and anti-androgens were evaluated to determine how firmly the DA-CAOS concept is supported and with what level of statistical certainty the results may be extrapolated to lower doses in humans. Underlying assumptions of the DA-CAOS concept were tested for accuracy and consistency against data for two human pharmaceuticals and its logical predictions were compared to human clinical and epidemiological experience. Those analyses revealed that DA-CAOS is scientifically untenable. Therefore, an alternative approach was developed - the Human-Relevant Potency-Threshold (HRPT) - that appears to fit the data better and avoids the contradictions inherent in the DA-CAOS concept. The proposed approach recommends application of independent action for phthalates and other chemicals with potential anti-androgenic properties at current human exposure levels.

RANKL inhibition is an effective adjuvant for docetaxel in a prostate cancer bone metastases model.

BACKGROUND: Docetaxel induces an anti-tumor response in men with advanced prostate cancer (PCa); however, the side effects associated with docetaxel treatment can be severe, resulting in discontinuation of therapy. Thus, identification of an effective adjuvant therapy to allow lower doses of docetaxel is needed. Advanced PCa is typically accompanied by skeletal metastasis. Receptor activator of NFkB ligand (RANKL) is a key pro-osteoclastic factor. Targeting RANKL decreases establishment and progression of PCa growth in bone in murine models. METHODS: The efficacy of inhibiting RANKL, using a recombinant soluble RANK extracellular domain fused with the immunoglobulin Fc domain (RANK-Fc), was tested as an adjuvant therapy with docetaxel for PCa bone metastasis in a murine intra-tibial model. RESULT: The combination of RANK-Fc and docetaxel reduced tumor burden in bone greater than either treatment alone. CONCLUSION: The combination of docetaxel with a RANKL-inhibiting agent merits further investigation for treatment of advance PCa.

A solution-processed 1.53 mum quantum dot laser with temperature-invariant emission wavelength.

Sources of coherent, monochromatic short-wavelength infrared (1-2 mum) light are essential in telecommunications, biomedical diagnosis, and optical sensing. Today's semiconductor lasers are made by epitaxial growth on a lattice-matched single-crystal substrate. This strategy is incompatible with integration on silicon. Colloidal quantum dots grown in solution can, in contrast, be coated onto any surface. Here we show a 1.53 mum laser fabricated using a remarkably simple process: dipping a glass capillary into a colloidal suspension of semiconductor quantum dots. We developed the procedures to produce a smooth, low-scattering-loss film inside the capillary, resulting in a whispering gallery mode laser with a well-defined threshold. While there exist three prior reports of optical gain in infrared-emitting colloidal quantum dots [1,2,3], this work represents the first report of an infrared laser made using solution processing. We also report dlambda(max)/dT, the temperature-sensitivity of lasing wavelength, of 0.03 nm/K, the lowest ever reported in a colloidal quantum dot system and 10 times lower than in traditional semiconductor quantum wells.

Room-temperature amplified spontaneous emission at 1300 nm in solution-processed PbS quantum-dot films.

We report room-temperature amplified spontaneous emission and spectral narrowing at infrared wavelengths in solution-processed films made up of PbS quantum-dot nanocrystals. The results are relevant to optical amplification and lasing integrated upon a variety of substrates. The active optical medium operates at room temperature without any additional matrix material, providing an optical gain of 260 cm(-1) and a pump threshold of 1 mJ/cm(-2). Nanocrystals synthesized in an aqueous solution and stabilized by use of short ligands result in high quantum-dot volume fractions in solid films and in a redshift emission relative to absorption.

Optical control over photoconductivity in polyferrocenylsilane films.

We report the study and elucidate the origin of the photoconductivity of polyferrocenylsilanes achieved through photooxidation performed by ultraviolet irradiation in the presence of chloroform. The persistence over months of the changes in the optoelectronic properties allowed more detailed studies of the charge photogeneration process. The photocurrent spectrum mimics that of the absorption indicating that the photooxidized material is not a mechanical mixture of oxidized and unoxidized polymer units. Photomodulation spectroscopy revealed the existence of long-lived photoexcited states with a lifetime in the millisecond range. They have been interpreted as trapped excitons at the oxidized sites where the polymer is deformed due to the presence of the chloroform derived counter ions. Because of the relatively long lifetime of the trapped excitons they can dissociate and the formed charge carriers can be separated in an externally applied electric field. The effect of the polymer chain deformation around the oxidized unit extends over the neighboring polymer units. In light of the potential applications of this class of polymers in various electronic and photonic devices, the clarification of such a basic process as the photocurrent generation will be a key factor for further technological development.

The minimum speech test battery in profound unilateral hearing loss.

OBJECTIVE: Individuals with monaural hearing experience disadvantages compared with normal hearing counterparts because of the loss of the head shadow effect, the squelch effect, and binaural summation. In this study the Minimum Speech Test Battery (MSTB), a battery designed to document word recognition in bilaterally hearing impaired cochlear implant candidates, was administered to unilaterally hearing-impaired and normal hearing subjects to study its possible use in measuring hearing difficulty in monaural subjects. STUDY DESIGN: Repeated measures design with the MSTB administered in sound-field in a sound-isolated booth in 1) quiet; 2) speech toward good ear, noise (+10 dB S/N) toward impaired ear; 3) speech toward impaired ear, noise toward good ear; and 4) bilateral speech and noise. SETTING: Academic otologic practice. PATIENTS: Ten adults with normal hearing and 10 adults with normal or near-normal hearing in one ear and profound hearing loss in the contralateral ear. MAIN OUTCOME MEASURES: The MSTB, composed of the Consonant-Nucleus-Consonant (CNC) test and the Hearing In Noise Test (HINT). RESULTS: As expected, performance differences between the groups were not found in quiet conditions. Analysis of variance and regression analysis confirmed that the impaired group performed significantly worse than control subjects on HINT testing when noise was directed toward the good ear. Analysis of variance and regression analysis confirmed that the impaired group performed significantly worse than control subjects on CNC testing when noise was directed toward the good ear and in bilateral noise. CONCLUSIONS: The MSTB may be useful in measuring the hearing difficulty of patients with monaural hearing.

Mastoid oscillation in canalith repositioning for paroxysmal positional vertigo.

OBJECTIVE: The canalith repositioning procedure (CRP) was developed to treat paroxysmal positional vertigo (PPV). Successful CRP results in cessation of PPV and positional nystagmus. Mastoid oscillation (MO) has been advocated to enhance the efficacy of CRP. The authors sought to objectively determine the effect of MO on CRP. STUDY DESIGN: Retrospective review. SETTING: Ambulatory referral center. PATIENTS: Patients with PPV seen from 1993 through 1999 (N = 168). INTERVENTIONS: Canalith repositioning procedure performed without MO (n = 104) and performed with MO (n = 64). MAIN OUTCOME MEASURE: Presence or absence of nystagmus on Dix-Hallpike testing 6 weeks after CRP. RESULTS: Eighty-four percent of patients treated with MO had resolution, and 16% had persistent nystagmus. Seventy-three percent of patients without MO had resolution, and 27% had persistent nystagmus. Although suggesting a trend, the difference did not reach the level of significance (p = 0.151). CONCLUSIONS: Mastoid oscillation does not significantly enhance the efficacy of the CRP.

Time-resolved luminescence in conducting polymer/antidot nanocomposites.

We report modification of the structure and properties of conjugated polymers through controlled embedding wide-gap nanocrystals (antidots) within the polymer matrix. Investigations were carried out by means of stationary and time-resolved photoluminescence. Antidots strongly modify the luminescence spectrum of poly(p-phenylene vinylene) but have almost no influence on the spectrum of poly(2-(6-cyano-6'-methylheptyloxy)-1, 4-phenylene. We explain this observation with respect to the different chain structure and electron density distribution in these two materials. The temporal evolution of luminescence spectra in polymer/antidot composites contains a series of characteristic times. The shortest of these (0.35-0.6 ns) are independent of antidot material and characterize processes in the polymer matrix. Larger times considerably exceeding 1 ns are composition-sensitive and attributable to carrier capture by nanocrystals. The qualitative character of the modification of luminescence spectra associated with the inclusion of antidots depends strongly on the characteristics of the polymer matrices and more weakly on the antidot material. This suggests that the predominant effect of the nanocrystals relates to the modification of the matrix near the polymer-inorganic interface.

Occupational hazard evaluation of p-bromobenzyl bromide from tests for genotoxicity.

As part of an occupational hazard evaluation, p-bromobenzyl bromide (p-BBB) was evaluated for genotoxic activity in the Ames microbial mutagenicity assay, the alkaline elution assay for DNA strand breaks in rat hepatocytes and the in vitro chromosome aberration assay in Chinese hamster ovary cells. The compound produced equivocal results in the microbial mutagenicity assay but was negative in the alkaline elution assay for DNA strand breaks in rat hepatocytes. The compound produced weakly positive results in the in vitro chromosome aberration assay. There was substantial cytotoxicity in all three assays. It is concluded that p-BBB is weakly genotoxic.

Cochlear implantation in sudden bilateral sensorineural hearing loss.

Although 1-4% of all cases of sudden sensorineural hearing loss (SSHL) are bilateral, all such patients reported to date have experienced significant recovery of hearing in at least one ear. We report a case of profound, bilateral idiopathic SSHL without recovery which was treated with cochlear implantation; the first such report to our knowledge. The patient achieved open-set spondee recognition. Individuals with sudden bilateral hearing loss in whom treatable causes have been eliminated may benefit from cochlear implantation.

Measurement of facial movement with computer software.

OBJECTIVE: To adapt desktop computer software to objectively grade facial movement. DESIGN: The criteria of the facial nerve grading system by House and Brackmann, the current "gold standard," are prone to ambiguous interpretation. Proposed objective grading systems compare the movement of points on each side of the face or use subtraction and thresholding of digitized images of the face to yield images that represent moving areas of the face. The movement of a point on the face and the area of motion determined by digital subtraction were compared during an increasing smile in healthy subjects. The Nottingham system (calculated using measurement of the movement of 4 points on the face) using desktop computer software (Adobe Photoshop 3.0, Adobe Systems Inc, Mountain View, Calif) to measure movement of the points was compared with the system by House and Brackmann. The computer software was used to subtract digitized images and derive a facial movement score, which was compared with the scores of the systems by Nottingham and House and Brackmann. SETTING: Academic otologic practice. STUDY PARTICIPANTS: Nine patients with varying degrees of facial nerve disability and 7 individuals with normal facial nerve function. RESULTS: The movement of the oral commissure compared with the apparent area of movement of the face determined by digital subtraction had high intersubject variability. In patients with facial weakness, the Nottingham score had a correlation coefficient of -0.97 compared with the House and Brackmann grade, and the digital subtraction score had a correlation coefficient of -0.62 (paired Student t test). CONCLUSIONS: The desktop computer software can be used to calculate the Nottingham score. Digital subtraction as a measure of facial function warrants further study.

Sudden sensorineural hearing loss following nonotologic, noncardiopulmonary bypass surgery.

OBJECTIVES: To report 3 cases of sudden sensorineural hearing loss (SSHL) following nonotologic surgery in which cardiopulmonary bypass (CPB) surgery was not involved and to review reports in the literature of similar cases. DATA SOURCES: Clinical records and MEDLINE and Healthstar databases. STUDY SELECTION: Reports in the world literature of cases of SSHL following nonotologic, non-CPB surgery. DATA SYNTHESIS: While said to be more common after CPB surgery, fewer than 20 cases of SSHL following non-otologic, non-CPB surgery have been reported. A number of proposed causes of SSHL temporally related to non-otologic, non-CPB surgery have been theorized; however, the true cause is unknown. This report presents 3 cases of SSHL following nonotologic, non-CPB surgery. Two patients had profound unilateral loss; 1 had moderate bilateral loss. None of the patients demonstrated recovery despite diuretic and prednisone therapy; in approximately 30% of the cases reported to date, the patients experienced significant improvement. CONCLUSIONS: Sudden sensorineural hearing loss following nonotologic, non-CPB surgery is rare, and its cause remains unknown. The scarcity of reports of SSHL following nonotologic, non-CPB surgery raises the possibility that the apparent association may be spurious.