2,076 research outputs found
The Role of the Spleen in Lymphocyte Migration
In all species studied so far it was found that more lymphocytes migrate to the spleen than to all the lymph nodes together. Specific molecules on lymphocytes and endothelial cells regulate their entry into lymph nodes, but none of the known molecules play a role in homing to the spleen. The splenic compartments, comprising the red pulp, marginal zone, periarterial lymphatic sheath (PALS) and follicles, all show different kinetics for migrating lymphocytes. By combining 51Cr lymphocyte labeling with morphometry and two color immunohistochemistry, the migratory route of lymphocyte subsets can be followed through the spleen and absolute numbers of lymphocytes calculated in each compartment. T lymphocytes home preferentially to the PALS and B lymphocytes home not only to follicles but also in large numbers to the marginal zone and red pulp. CD4+ and CD8+ lymphocytes migrate similarly at early time points, but at 24 hours CD4+ lymphocytes are preferentially found in the PALS with CD8+ lymphocytes in the red pulp and marginal zone. The functional significance of the different routes of lymphocytes through the spleen has yet to be defined in relationship to specific immune functions and regulatory factors on splenic lymphocyte homing
What is the clinical relevance of different lung compartments?
The lung consists of at least seven compartments with relevance to immune reactions. Compartment 1 - the bronchoalveolar lavage (BAL), which represents the cells of the bronchoalveolar space: From a diagnostic point of view the bronchoalveolar space is the most important because it is easily accessible in laboratory animals, as well as in patients, using BAL. Although this technique has been used for several decades it is still unclear to what extent the BAL represents changes in other lung compartments. Compartment 2 - bronchus-associated lymphoid tissue (BALT): In the healthy, BALT can be found only in childhood. The role of BALT in the development of the mucosal immunity of the pulmonary surfaces has not yet been resolved. However, it might be an important tool for inhalative vaccination strategies. Compartment 3 - conducting airway mucosa: A third compartment is the bronchial epithelium and the submucosa, which both contain a distinct pool of leukocytes (e.g. intraepithelial lymphocytes, IEL). This again is also accessible via bronchoscopy. Compartment 4 - draining lymph nodes/Compartment 5 - lung parenchyma: Transbronchial biopsies are more difficult to perform but provide access to two additional compartments - lymph nodes with the draining lymphatics and lung parenchyma, which roughly means "interstitial" lung tissue. Compartment 6 - the intravascular leukocyte pool: The intravascular compartment lies between the systemic circulation and inflamed lung compartments. Compartment 7 - periarterial space: Finally, there is a unique, lung-specific space around the pulmonary arteries which contains blood and lymph capillaries. There are indications that this "periarterial space" may be involved in the pulmonary host defense
Suitable Design for Electromagnetic Pulse Processes
Basic conventional production processes, such as arc welding or forming, are more or less
thoroughly investigated, reliable process guidelines have been developed and trained
engineers are available. This allows them to be put into use usually fast, thus facilitating a
wide application.
The usage of electromagnetic pulse processes, on the contrary, still lacks a broad
propagation. Despite having a history reaching back several decades, these processes are
mostly limited to niche applications. Admittedly, theoretical considerations have been made
and various experiments have been carried out. However, when a given joining or forming
task needs to be realized with electro-magnetic force, a huge invest is necessary even before
the first part is made. This involves the design of the machine, especially of the tool coil, as
well as the design of the workpieces to be processed.
In industrial environmentsthis challenge is tackled step by step: After the theoretical product
concept in close collaboration with the customer, numerical and experimental trials are
carried out. In many cases, iterations are necessary and both geometry and process are
optimized. The experimental trials can be conducted with universal sheet welding tool coils
or tube compression tool coils with custom field shapers. This procedure allows keeping the
prototyping costs low, but at the same time provides valid information on the feasibility in
general, the requirements to the workpieces, the design of the tool coil and the properties of
the pulse generator. Subsequently, the tool coil is designed and manufactured according to
the prior findings. The pulse generator as modular component is assembled and adapted to
the customer’s requirements.
The iterative product and process design is the most important phase of the whole procedure,
which is in accordance with good project management. It significantly lowers the risk of an
expensive project cancellation during the late steps
Carbon radio recombination lines from gigahertz to megahertz frequencies towards Orion A
Context. The combined use of carbon radio recombination lines (CRRLs) and the
158 m-[CII] line is a powerful tool for the study of the energetics and
physical conditions (e.g., temperature and density) of photodissociation
regions (PDRs). However, there are few observational studies that exploit this
synergy. Aims. Here we explore the relation between CRRLs and the 158
m-[CII] line in light of new observations and models. Methods. We present
new and existing observations of CRRLs in the frequency range 0.15--230 GHz
with ALMA, VLA, the GBT, Effelsberg 100m, and LOFAR towards Orion~A (M42). We
complement these observations with SOFIA observations of the 158 m-[CII]
line. We studied two PDRs: the foreground atomic gas, known as the Veil, and
the dense PDR between the HII region and the background molecular cloud.
Results. In the Veil we are able to determine the gas temperature and electron
density, which we use to measure the ionization parameter and the photoelectric
heating efficiency. In the dense PDR, we are able to identify a layered PDR
structure at the surface of the molecular cloud to the south of the Trapezium
cluster. There we find that the radio lines trace the colder portion of the
ionized carbon layer, the C/C/CO interface. By modeling the emission of
the ~m-[CII] line and CRRLs as arising from a PDR we derive a thermal
pressure K cm and a radiation field
close to the Trapezium. Conclusions. This work provides
additional observational support for the use of CRRLs and the 158 m-[CII]
line as complementary tools to study dense and diffuse PDRs, and highlights the
usefulness of CRRLs as probes of the C/C/CO interface.Comment: 18 pages, 16 figures, accepted for publication in A&
Probing of local ferroelectricity in BiFeO3 thin films and (BiFeO3)m(SrTiO3)m superlattices
Ferroelectric BiFeO3 thin films and artificial superlattices of
(BiFeO3)m(SrTiO3)m (m~ 1 to 10 unit cells) were fabricated on (001)-oriented
SrTiO3 substrates by pulsed laser ablation. The variation of leakage current
and macroscopic polarization with periodicity was studied. Piezo force
microscopy studies revealed the presence of large ferroelectric domains in the
case of BiFeO3 thin films while a size reduction in ferroelectric domains was
observed in the case of superlattice structures. The results show that the
modification of ferroelectric domains through superlattice, could provide an
additional control on engineering the domain wall mediated functional
properties.Comment: 14 pages, To be published in J. Mag. Mag Mater. proceedings of EMRS
200
- …