tip position Dotaz Zobrazit nápovědu
We study the conductance of N-heterocyclic carbene-based (NHC) molecules on gold by means of first-principles calculations based on density-functional theory and non-equilibrium Green's functions. We consider several tip structures and find a strong dependence of the position of the NHC molecular levels with the atomistic structure of the tip. The position of the lowest unoccupied molecular orbital (LUMO) can change by almost 0.8 eV with tip shape. Through an analysis of the net charge transfer, electron redistribution and work function for each tip structure, we rationalize the LUMO shifts in terms of the sum of the work function and the maximum electrostatic potential arising from charge rearrangement. These differences in the LUMO position, effectively gating the molecular levels, result in large conductance variations. These findings open the way to modulating the conductance of NHC-based molecular circuits through the controlled design of the tip atomistic structure.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Field-enhanced metal-induced solid phase crystallization (FE-MISPC) of amorphous silicon is scaled down to nanoscale dimensions by using a sharp conductive tip in atomic force microscopy (AFM) as one of the electrodes. The room temperature process is driven by the electrical current of the order of 100 pA between the tip and the bottom nickel electrode. This results in energy transfer rates of 30-50 nJ s(-1). Amplitude of the current is limited by a MOSFET transistor to avoid electrical discharge from parasitic parallel capacitance. Limiting the current amplitude and control of the transferred energy (approximately 100 nJ) enables formation of silicon crystals with dimensions smaller than 100 nm in the amorphous film. Formation of the nanocrystals is localized by the AFM tip position. The presence of nanocrystals is detected by current-sensing AFM and independently corroborated by micro-Raman spectroscopy. The nanocrystal formation is discussed based on a model considering microscopic electrical contact, thermodynamics of crystallization and silicide formation.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Tip growth is one of the most preferable models in the study of plant cell polarity; cell wall deposition is restricted mainly to a certain area of the cell, and cell expansion at this specific area leads to the development of tubular outgrowth. Tip-growing root hairs are well-established systems for such studies, because their lateral position within the root makes them easily accessible for experimental approaches and microscopic observations. Fundamental structural and molecular processes driving tip growth are exocytosis, endocytosis, and all aspects of vesicular and endosomal dynamic trafficking, as related to targeted membrane flow. Study of vesicles and endosomes in living root hairs, however, is rather difficult, due to their small size and due to the resolution limits of conventional light microscopes. Here we present noninvasive approaches for visualizing vesicular and endosomal compartments in the tip of growing root hairs using electronic light microscopy, contrast-enhanced video light microscopy, and confocal laser scanning microscopy (CLSM). These methods allow utilizing the maximum resolution of the light microscope. Together with protocols for appropriate preparation of living plant samples, the described methods should help improve our understanding on how tiny vesicles and endosomes support the process of tip growth in root hairs.
- MeSH
- Arabidopsis růst a vývoj ultrastruktura MeSH
- endozomy metabolismus ultrastruktura MeSH
- exocytóza genetika MeSH
- konfokální mikroskopie MeSH
- kořeny rostlin růst a vývoj ultrastruktura MeSH
- molekulární biologie metody MeSH
- polarita buněk MeSH
- transport proteinů MeSH
- transportní vezikuly metabolismus ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
PURPOSE OF THE STUDY: This study investigated the relationship between the position of the tip of the coracoid process (CP) relative to the glenoid with subscapularis (Ssc) tears. We hypothesized that the coracoid tip is more inferior, lateral and posterior in patients with Ssc tear. MATERIAL AND METHODS: This research enrolled 34 isolated Ssc tears and 44 controls. We introduced the axial central glenoid-coracoid angle (acGCA) and sagittal central glenoid-coracoid angle (scGCA) to evaluate the position of the tip of the CP relative to the glenoid center on MRI images. In both groups, acGCA, scGCA on MRI and critical shoulder angle (CSA), glenoid inclination (GI) on true anterior-posterior shoulder radiography were evaluated. RESULTS: When both groups were compared in terms of acGCA, the acGCA values of the Ssc tear group were significantly higher than the control group (p<0.001). The best cut-off value of acGCA for Ssc tears was 28.3°. acGCA values higher than 28.3° showed 93.3% sensitivity and 93.1% specificity for Ssc tears (likelihood ratio:13.53, AUC: 0.979, 95% CI of AUC: 0.950- 0.999). In terms of acGCA, the power analysis between Ssc tears group and control group was 99.9% between Ssc tears and the control group (effect size d=2.63). When both groups were compared in terms of scGCA, the scGCA values of the Ssc tear group were significantly higher than the control group (p<0.001). The best cut-off value of scGCA for Ssc tears was 41.4°. Scores of scGCA greater than 41.8° showed 80% sensitivity and 89.7% specificity for Ssc tears (likelihood ratio: 7.73, AUC: 0.899 95% CI of AUC: 0.837-0.958). In terms of scGCA, the power analysis between Ssc tear and control group was 99.8% (effect size d=1.23). When both groups were compared in terms of CSA and GI; CSA and GI values in the Ssc tear group were significantly higher (p<0.001 and p<0.012, respectively). CONCLUSIONS: AcGCA values higher than 28.3° indicate that the coracoid tip is located more laterally and posteriorly; scGCA values higher than 41.8° indicate that the coracoid tip is located more inferiorly and these two new indexes are showing that more laterally, posteriorly and inferiorly coracoid tip is related to subscapularis tears. KEY WORDS: coracoid process, subscapularis tear, coracoid morphology, scapula morphology.
- MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- magnetická rezonanční tomografie * metody MeSH
- poranění rotátorové manžety * diagnostické zobrazování MeSH
- processus coracoideus * zranění diagnostické zobrazování MeSH
- ramenní kloub diagnostické zobrazování MeSH
- senzitivita a specificita MeSH
- studie případů a kontrol MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The shape and form of the flagellated eukaryotic parasite Leishmania is sculpted to its ecological niches and needs to be transmitted to each generation with great fidelity. The shape of the Leishmania cell is defined by the sub-pellicular microtubule array and the positioning of the nucleus, kinetoplast and the flagellum within this array. The flagellum emerges from the anterior end of the cell body through an invagination of the cell body membrane called the flagellar pocket. Within the flagellar pocket the flagellum is laterally attached to the side of the flagellar pocket by a cytoskeletal structure called the flagellum attachment zone (FAZ). During the cell cycle single copy organelles duplicate with a new flagellum assembling alongside the old flagellum. These are then segregated between the two daughter cells by cytokinesis, which initiates at the anterior cell tip. Here, we have investigated the role of the FAZ in the morphogenesis of the anterior cell tip. We have deleted the FAZ filament protein, FAZ2 and investigated its function using light and electron microscopy and infection studies. The loss of FAZ2 caused a disruption to the membrane organisation at the anterior cell tip, resulting in cells that were connected to each other by a membranous bridge structure between their flagella. Moreover, the FAZ2 null mutant was unable to develop and proliferate in sand flies and had a reduced parasite burden in mice. Our study provides a deeper understanding of membrane-cytoskeletal interactions that define the shape and form of an individual cell and the remodelling of that form during cell division.
- MeSH
- buněčná membrána MeSH
- cytokineze MeSH
- cytoskelet metabolismus MeSH
- flagella fyziologie ultrastruktura MeSH
- interakce hostitele a parazita * MeSH
- Leishmania růst a vývoj ultrastruktura MeSH
- leishmanióza parazitologie MeSH
- morfogeneze * MeSH
- myši inbrední BALB C MeSH
- myši MeSH
- protozoální proteiny genetika metabolismus MeSH
- Psychodidae parazitologie MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- protozoální proteiny MeSH
Terminating the tip of an atomic force microscope with a CO molecule allows data to be acquired with a well-known and inert apex. Previous studies have shown conflicting results regarding the electrostatic interaction, indicating in some cases that the negative charge at the apex of the CO dominates, whereas in other cases the positive charge at the end of the metal tip dominates. To clarify this, we investigated [Formula: see text](111). [Formula: see text] is an ionic crystal and the (111) surface does not possess charge inversion symmetry. Far from the surface, the interaction is dominated by electrostatics via the negative charge at the apex. Closer to the surface, Pauli repulsion and CO bending dominate, which leads to an unexpected appearance of the complex 3-atom unit cell. We compare simulated data in which the electrostatics are modeled by point particles versus a charge density calculated by DFT. We also compare modeling Pauli repulsion via individual Lennard-Jones potentials versus a total charge density overlap. In doing so, we determine forcefield parameters useful for future investigations of biochemical processes.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Transjugular intrahepatic portosystemic shunt (TIPS) is a side-to-side portocaval shunt for threatening complications of portal hypertension. TIPS effectively decreases portal hypertension connecting the hepatic and portal vein with an expandable metal stent without the mortality and morbidity of an open surgical procedure. Technical success can be achieved in over 90% of patients, with procedure related mortality of 1-2%. The main problem is stenosis or occlusion of the shunt by neo-intimal hyperplasia narrowing the lumen of the shunt in 20-80% of patients during 6-12 months, but fortunately, most stenotic stents can be revised successfully. Recent indications for TIPS are acute variceal hemorrhage refractory to endoscopic treatment and recurrent variceal bleeding despite sclerotherapy or band ligation. TIPS insertion in the treatment of refractory ascites seems to be promising.
Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is very important for the high performance of the CE-ESI-MS devices and their applications for highly sensitive analyses of ionogenic compounds. In this study, we utilize a nanoflow sheath-liquid CE-ESI-MS interface composed of a quartz emitter and a separation fused silica capillary treated by etching, which are threaded to cross coupling for sheath liquid and electrode connection. Specifically, we have tested the ability of the interface to decouple the ESI potential from the separation potential at different positions of the separation capillary and ESI emitter tube tips. The interface with the separation capillary tip protruding the emitter tip by 20 μm did not provide sufficient robustness. The real ESI potential (delivered as 2.0 kV from the independent high voltage power supply HV2) ranged from 2.1 kV to 4.5 kV depending on the applied separation voltage (12.0-20.0 kV, provided by the power supply HV1) and electric conductivity of the background electrolyte (BGE) used. The interface robustness was partially improved when the capillary tip was aligned with the emitter tip. However, the complete decoupling of the spray and separation potentials was achieved only when the capillary tip was retracted 20 μm inside the emitter. In this arrangement, the ESI potential was stable and independent of both the separation potential (voltage) and the BGE conductivity. Moreover, this setting provided better sensitivity for the CE-ESI-MS analysis of selected drugs and benzylpyridinium cations than the setup with the capillary tip aligned with or protruding the emitter tip.
- Klíčová slova
- Capillary electrophoresis, ESI potential decoupling, ESI-MS interface, Electrospray ionization, Mass spectrometry, Spray potential,
- Publikační typ
- časopisecké články MeSH
The most commonly used permanent venous access devices in cancer patients are the port, PICC port and PICC catheter (peripherally inserted central catheter). It is always necessary to consider the type of venous access needed for each individual cancer patient. Implantation should be performed using modern instruments to minimize the risk of early and late complications and thereby a delay in oncological treatment. The use of ultrasound is recommended at all stages of introduction. Precise tip placement of the central catheter in the sinoatrial junction region further reduces the number of thromboses arising in the catheter. A trend towards the treatment of catheter infections is certainly to maintain the venous access without compromising the patients health. Permanent venous access devices allow the application of chemotherapy and repeated blood sample collections with minimal impact on the quality of life in cancer patients.
- Klíčová slova
- port, PICC, cancer patient, complication, tip position,
- MeSH
- katetrizace centrálních vén * MeSH
- katétrové infekce * MeSH
- kvalita života MeSH
- lidé MeSH
- nádory * MeSH
- periferní katetrizace * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The purpose of the study was to compare the stability of the plate osteosyntheses of intra-articular calcaneal fractures using various types of a sustentacular screw insertions. A geometrical model of a calcaneal fracture was created. The fracture was fixed with a plate and screws with a uniform distribution. The individual models differed regarding the position of the sustentacular screw. The screw was inserted using three different variants: Model A: into the tip of sustentaculum tali, Model B: under the sustentaculum tali, and Model C: into the inferior peripherial rim of the sustentacular fragment. In all three variants, the screw was either locked into the plate via threads or unlocked. The model was loaded with force in the vertical direction. The stiffness of individual models was evaluated using the finite element method, which was expressed as the maximum force (Fmax) that the system was able to transmit and by determining the magnitude and distribution of reduced stress (σred) on the individual parts of the model of a fixed calcaneal fracture. The greatest stiffness of the system was observed in the Model B (Fmax = 335.8 N). The least stiffness was observed in Model C (Fmax = 296.3 N). This model also produced the greatest load on bone tissue was observed (σmaxred = 67.5 MPa). The least load on bone tissue was measured in Model B (σmaxred = 53.7 MPa). The load on the plate was similar in all three models (814.0-820.0 MPa). The analyses suggest that in a plate osteosynthesis of a calcaneal fracture, the insertion of a sustentacular screw under the tip of the sustentaculum tali is acceptable in terms of osteosynthesis stability. This sustentacular screw position reduces the risk of the screw penetrating into the talocalcaneal joint.
- Klíčová slova
- Sustentacular screw, calcaneus, finite element method, fracture, stability,
- MeSH
- biomechanika MeSH
- fraktury kostí * chirurgie MeSH
- kostní destičky MeSH
- kostní šrouby MeSH
- lidé MeSH
- patní kost * chirurgie MeSH
- vnitřní fixace fraktury MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
