Detection of volatile
organic compounds (VOCs) at room temperature
(RT) currently remains a challenge for metal oxide semiconductor (MOS)
gas sensors. Herein, for the first time, we report on the utilization
of porous SnO2 thin films for RT detection of VOCs by defect
engineering of oxygen vacancies. The oxygen vacancies in the three-dimensional-ordered
SnO2 thin films, prepared by a colloidal template method,
can be readily manipulated by thermal annealing at different temperatures.
It is found that oxygen vacancies play an important role in the RT
sensing performances, which successfully enables the sensor to respond
to triethylamine (TEA) with an ultrahigh response, for example, 150.5–10
ppm TEA in a highly selective manner. In addition, the sensor based
on oxygen vacancy-rich SnO2 thin films delivers a fast
response and recovery speed (53 and 120 s), which can be further shortened
to 10 and 36 s by elevating the working temperature to 120 °C.
Notably, a low detection limit of 110 ppb has been obtained at RT.
The overall performances surpass most previous reports on TEA detection
at RT. The outstanding sensing properties can be attributed to the
porous structure with abundant oxygen vacancies, which can improve
the adsorption of molecules. The oxygen vacancy engineering strategy
and the on-chip fabrication of porous MOS thin film sensing layers
deliver great potential for creating high-performance RT sensors.
Van der Waals p-n junctions of 2D materials present great potential for electronic devices due to the fascinating properties at the junction interface. In this work, an efficient gas sensor based on planar 2D van der Waals junctions is reported by stacking n-type and p-type atomically thin MoS 2 films, which are synthesized by chemical vapor deposition (CVD) and soft-chemistry route, respectively. The electrical conductivity of the van der Waals p-n junctions is found to be strongly affected by the exposure to NO 2 at room temperature (RT). The MoS 2 p-n junction sensor exhibits an outstanding sensitivity and selectivity to NO 2 at RT, which are unavailable in sensors based on individual n-type or p-type MoS 2 . The sensitivity of 20 ppm NO 2 is improved by 60 times compared to a p-type MoS 2 sensor, and an extremely low limit of detection of 8 ppb is obtained under ultraviolet irradiation. Complete and very fast sensor recovery is achieved within 30 s. These results are superior to most of the previous reports related to NO 2 detection. This work establishes an entirely new sensing platform and proves the feasibility of using such materials for the high-performance detection of gaseous molecules at RT.
BackgroundOrphan drugs are intended to treat, prevent or diagnose rare diseases. In recent years, China healthcare policy makers and patients have become increasingly concerned about orphan drug issues. However, very few studies have assessed the availability and affordability of orphan drugs for rare diseases in China. The aim of this study was to provide an overview of the availability and affordability of orphan drugs in China and to make suggestions to improve patient access to orphan drugs.MethodsTwo components of the availability of orphan drugs were examined. Market availability was assessed by the extent to which orphan drugs were marketed in China with a comparison to orphan drugs in international markets, such as the U.S., EU and Japan. We conducted surveys and collected data from 24 tertiary public hospitals in China to measure hospital-level availability of orphan drugs. The affordability of orphan drugs was calculated using hospital dispensary prices and was expressed as days of average daily income required for the cost of a course of treatment. Affordability was also analyzed under the Chinese basic medical insurance system.ResultsOrphan drugs approved in the U.S., EU and Japan had 37.8 %, 24.6 % and 52.4 % market availability in China, respectively. Median availability of 31 orphan drugs surveyed at the 24 tertiary public hospitals was 20.8 % (very low). Within a periodic treatment course, the average treatment cost of 23 orphan drugs is approximately 4, 843. 5 USD, which equates to 505.6 days of per capita net income for an urban resident with a middle income (187.4 days for a high-income urban resident) or 1,582.8 days’s income for a rural resident with a middle income (657.2 days for a high-income rural resident). Except for homoharringtonine, 22 orphan drugs for 14 rare diseases were unaffordable for the most of residents in China. With 5 % out-of-pocket expenses, only three generics could be afforded by middle-income residents, whereas seven drugs for high-income urban residents.ConclusionsThe Chinese government can take more responsibility for improving the availability and affordability of orphan drugs through setting up incentive policies and public platforms for sharing of orphan drug information. Control of the high price of orphan drugs, combined with a joint funding model from both government and private enterprise can efficiently reduce the economic burden of affected patients in China.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-016-0392-4) contains supplementary material, which is available to authorized users.
We report the electrical, magnetic and thermal measurements on a layered cobalt oxyhydrate Na0.31CoO2·1.3H2O. Bulk superconductivity at 4.3 K has been confirmed, however, the measured superconducting fraction is relatively low probably due to the sample's intrinsic two-dimensional characteristic. The compound exhibits weak-coupled and extreme type-II superconductivity with the average energy gap ∆a(0) and the Ginzburg-Landau parameter κ of ∼ 0.50 meV and ∼ 140, respectively. The normalized electronic specific heat data in the superconducting state well fit the T 3 dependence, suggesting point nodes for the superconducting gap structure.
A short-course administration of galectin-9 significantly prolonged the survival of fully allogeneic cardiac allografts, which was associated with the suppression of Th1 and Th17 immune responses.
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