Infrared tunable, two colour-band photodetectors on flexible platforms using 0D/2D PbS-MoS2 hybrids.

Two-dimensional (2D) MoS2 nanosheets have been integrated with zero-dimensional (0D) PbS quantum dots to achieve a superior optical response extending to the short-wavelength infrared region along with a broadband visible response for multispectral photodetection. The 0D/2D hybrid nanostructures have been synthesized by a one pot, stabilizer-free solvothermal growth process. Microscopic and spectroscopic studies confirmed the formation of PbS QD decorated semiconducting 2H-MoS2 layers. The size tunable absorption features with longer photo-generated carrier lifetime of synthesized hybrid nanostructures indicate that the integration of PbS QDs in MoS2 could be a viable approach for fabricating two-colour band photodetectors, viz. visible broadband and wavelength selective short-wave IR photodetectors. Devices have also been demonstrated on polyethylene terephthalate substrates using a solution-based synthesis technique for flexible and ultrathin optoelectronic device applications. The photodetection performance of fabricated devices suggests that the synergic 0D/2D hybrid nanostructures are significantly superior to solution processed hybrid devices operating in the infrared region. The successful integration of 0D QDs in 2D materials may pave the way for novel, high performance, next-generation CMOS compatible flexible photonic devices.

Synergistic effect of polymer encapsulated silver nanoparticle doped WS2 sheets for plasmon enhanced 2D/3D heterojunction photodetectors.

Chemical doping and plasmonic enhanced photoresponsivity of two dimensional (2D) n-WS2/p-Si heterojunctions are demonstrated for the first time. Novel PVP coated Ag0 intercalation induced synthesis has led to the formation of impurity-free, chemically doped few-layer n-WS2 with reversed conductivity following the Maxwell-Wagner-Sillars interfacial effect. The resultant composite film exhibits excellent stability and tunable plasmonic absorption due to silver nanoparticles of different sizes. A sharp band-edge absorption of the hybrid material indicates the presence of spin-orbit coupled direct band gap transitions in WS2 layers, in addition to a broader plasmonic peak attributed to Ag nanoparticles. Stabilized Ag-nanoparticle (∼4-6 nm) embedded electron rich n-WS2 has been used to fabricate plasmon enhanced, silicon compatible heterojunction photodetectors. The detectors exhibited superior properties, possessing a photo-to-dark current ratio of ∼103, a very high responsivity (8.0 A W-1) and an EQE of 2000% under 10 V bias with a broad spectral photoresponse in the wavelength range of 400-1100 nm. The results provide a new paradigm for intercalant impurity-free metal nanoparticle assisted exfoliation of n-type few-layer WS2, with the nanoparticles playing a dual role towards the realization of 2D materials based broadband heterojunction optoelectronic devices by inducing chemical doping as well as tunable plasmon enhanced absorption.

A prototype ultrasound-guided laparoscopic radiofrequency ablation system.

BACKGROUND: Advanced laparoscopic procedures, particularly laparoscopic liver resection and ablation, may benefit from image-guided surgery techniques that involve interactive three-dimensional imaging and instrument tracking. METHODS: A prototype system for laparoscopic ultrasound-guided radiofrequency ablation was designed and implemented. This system uses an infrared camera to track instruments and runs on a personal computer. Features of the system include spatially registered ultrasound visualization, volume reconstruction, and interactive targeting. Targeting of accuracy studies was performed by directing a tracked needle to a phantom target. RESULTS: Ultrasound data collection and volume reconstruction can be achieved within minutes and interactively reviewed by the surgeon. Early results with phantom experiments demonstrate a targeting accuracy of 5 to 10 mm. CONCLUSIONS: These results support the further development of this and similar image-guided surgery systems for specific laparoscopic procedures. Eventually, rigorous clinical evaluation will be necessary to prove their value.

Unilateral pellucid marginal degeneration.

Pellucid marginal degeneration (PMD) is a rare and usually a bilateral condition. We report a case of typical PMD with a unilateral presentation.

Cytologic screening for the detection of cancer in the uterine cervix--a survey in Patna (India).

Cytologic screening of the uterine cervix of 10,012 married women of Patna (India) was conducted to find out precancerous and cancerous lesions in different age and parity groups. Of the "pap" smears, 80.1% were normal, 11.1% were inflammatory, 5.8% showed dyskaryosis and 2.8% had cellular profiles suggestive of malignancy. In higher age groups i.e., in 40-49 and 50-59 years, the percentage of inflammatory smears were increased to 15 and 35.8; and invasive carcinoma to 8.28 and 14.19, respectively. Higher parity groups (four and above) had greater incidence of invasive carcinoma (6.7%) than those of lower parity groups (1.88%).

Evidence that increased circulating 1 alpha, 25-dihydroxyvitamin D is the probable cause for abnormal calcium metabolism in sarcoidosis.

Mean plasma 1(alpha),25-dihydroxyvitamin D[1(alpha),25(OH)(2)D] was significantly increased and serum parathyroid hormone was suppressed in three patients with sarcoidosis and hypercalcemia. Prednisone lowered the mean plasma 1(alpha),25(OH)(2)D to normal range and corrected the hypercalcemia. To elucidate the mechanism for the increased sensitivity to vitamin D in this disorder, the effects of orally-administered vitamin D(2) were determined in seven normal subjects, four patients with sarcoidosis and normal calcium metabolism and three patients with sarcoidosis and a history of hypercalcemia who were normocalcemic when studied. Serum and urinary calcium, serum 25-hydroxyvitamin D (25-OHD), plasma 1(alpha),25(OH)(2)D and, in some studies, calcium balance were measured. Vitamin D(2), 250 mug a day for 12 d, produced little, if any, change in mean plasma 1(alpha),25(OH)(2)D and in urinary calcium in the normals and in the patients with normal calcium metabolism. In contrast, vitamin D(2) produced increases in plasma 1(alpha),25(OH)(2)D from concentrations which were within the normal range (20-55 pg/ml) to abnormal values and increased urinary calcium in two patients with abnormal calcium metabolism. In an abbreviated study in the third patient, vitamin D(2), 250 mug a day for 4 d, also increased plasma 1(alpha),25(OH)(2)D abnormally from a normal value. There was a highly significant correlation between plasma 1(alpha),25(OH)(2)D and urinary calcium. Serum 25-OHD and serum calcium remained within the normal range in all subjects and patients. These findings provide evidence that the defect in calcium metabolism in sarcoidosis probably results from impaired regulation of the production and(or) degradation of 1(alpha),25(OH)(2)D. Prednisone may act to correct the abnormal calcium metabolism by reducing circulating 1(alpha),25(OH)(2)D.

Nucleic acid interaction with VERO cells. A temperature barrier in the interaction pattern.

The interaction of VERO cell monolayers with spin (nitroxide)-(labeled polynucleotides (1(N)n) was examined by electron spin resonance (ESR) spectroscopy at various temperatures. Nitroxide labels covalently linked to (A)n, (dUfl)n, (U)n and (A)n . (U)n were used to monitor the interaction. The VERO cells were grown on small quartz plates with a cell viability of 95% or better and then used directly for the ESR studies. The ESR results indicated that the interaction between VERO cells and spin-labeled nucleic acids is temperature dependent. No temperature dependence was found when VERO cells were in contact with nitroxide radicals which were free in solution or covalently bound to Sepharose 4B. The temperature dependence established with nitroxide-labeled nucleic acids indicates that a temperature barrier must exist between 20 and 26 degrees C for the interaction between nucleic acids and VERO cells; namely, at 26 degrees C or above spin-labeled nucleic acids interact significantly with a VERO cell surface; whereas, at 20 degrees C the ESR signal reports no interaction. It is concluded that a temperature-dependent phase transition of membrane components or cell surface products active at 26 degrees C or above play a key role in the nucleic acid cell surface interaction process.

Acquired resistance to parathyroid hormone.

Studies are presented in a patient with pseudohypoparathyroidism who showed a partial response to parathyroid extract. Resistance to the extract was observed after its short-term administration for the gourth time. Serum from the patient contained antibodies of the gamma G globulin class which bound 125I-labelled bovine parathyroid hormone. Prior incubation of parathyroid hormone with the serum prevented the activation in vitro of adenylate cyclase from pork renal cortex. The antibodies were directed primarily toward the C-terminal portion of the molecule. Thus, clinical resistance to parathyroid hormone is attributed to specific antibodies.

On the lipolytic action of parathyroid hormone in man.

An investigation was carried out to determine whether bovine PTH stimulates lipolysis in human fat tissue, whether this action is mediated by cyclic adenosine 3', 5'-monophosphate and whether the N-terminal 1-34 peptide of bovine PTH is responsible for the lipolytic effect. Studies were also performed to determine if parathyroid extract (PTE) produces lipolysis in normal subjects and in patients with pseudohypoparathyroidism in whom there is a defect in the adenylate system in response to PTH in the renal cortex and presumably in the skeletal system as well. It was found that highly purified bovine PTH in the concentration range between 10(-9) M and 10(-5) M stimulated lipolysis in vitro by human fat in a dose-dependent manner. Significant increases in glycerol production were observed at concentrations of PTH as low as 10(-9) M and maximal increases were seen at 10(-6) M. The hormone significantly increased the concentration of cyclic adenosine 3' ,5'-monophosphate in fat tissue. The synthetic N-terminal 1-34 peptide of bovine PTH was as effective as the native hormone in stimulating glycerol production at a concentration of 10(-9) M-10(-6) M. PTE, 100 mU per kg per min for 30 min given intravenously, produced transient increases in the concentration of plasma free fatty acid in each of eight normal subjects, three patients with hypoparathyroidism and eight patients with pseudohypoparathyroidism. Purified bovine PTH also increased plasma free fatty acid in each of two normal subjects. It is concluded that PTH stimulates lipolysis in human subcutaneous fat, that this action of the hormone is mediated through cyclic adenosine 3', 5'-monophosphate and that the N-terminal 1-34 peptide portion of the hormone is responsible for this lipolytic action. Further, PTE stimulates lipolysis in vivo in man. There appears to be no defect in the adenylate cyclase system in the fat cell in response to PTH in patients with pseudohypoparathyroidism.

Demonstration of a diurnal variation in serum parathyroid hormone in primary and secondary hyperparathyroidism.

It had been reported previously that there is a diurnal variation in serum parathyroid hormone (PTH) in normal subjects but not in patients with primary hyperparathyroidism. Studies were performed to determine whether there is a diurnal variation in serum PTH in primary or secondary hyperparathyroidism and whether the nocturnal increase in serum PTH, if present, could be prevented by induced hypercalcemia. Serum PTH and calcium were measured in five normal subjects, two patients with pseudohypoparathyroidism, and fourteen patients with primary hyperparathyroidism, twelve of whom were subsequently found to have parathyroid adenomas. In the normals, there was a mean decline in serum PTH of 0.07 ng/ml before noon and a mean increase of 0.04 ng/ml after 8 PM. In primary hyperparathyroidism there was a mean decline in serum PTH before noon of 0.11 ng/ml and a mean increase of 0.11 ng/ml after 8 PM. In both groups, the lowest mean serum calcium values were noted between midnight and 6:00 AM. Patients with pseudohypoparathyroidism showed a nocturnal increase in serum PTH. In each of two normal subjects, two patients with primary hyperparathyroidism, and two patients with pseudohypoparathyroidism, calcium, 4 mg/kg body weight per hour for 4 hours (8:00 PM to 12 midnight), produced hypercalcemia and prevented the nocturnal increase in serum PTH. We have concluded that a diurnal variation in serum PTH often occurs in both normal subjects and in patients with primary or secondary hyperparathyroidism and that nocturnal increases in serum PTH can be prevented by induced hypercalcemia.

Electron spin resonance for detecting polyadenylate tracts in RNA's.

Electron spin resonance is used to detect RNA's that contain polyadenylate tracts. The method depends on the ability of RNA's that contain polyadenylate sequences to associate with poly(2'-deoxy-2'-fluoro)uridylic acid, which has been spin-labeled with 4-(2-iodoacetamido)-2,2,6,6-tetramethylpiperidinooxyl. The formation of the hybridization product can be detected by monitoring the decrease in mobility of the spin probe.