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1.
Swiss J Econ Stat ; 158(1): 10, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35528701

RESUMEN

Using a representative sample of European firms, we study whether financing constraints affect employers' investments in employee training and physical capital differently. We measure financing constraints with an index that combines survey and balance sheet data. We instrument this index with the non-performing loans ratio of the bank that provided the last loan to the firms or with the average ratio of banks in the local area. We find that financing constraints have no effect on investment in training, but substantially reduce investment in physical capital.

2.
Biomed Eng Online ; 20(1): 8, 2021 Jan 07.
Artículo en Inglés | MEDLINE | ID: mdl-33413423

RESUMEN

BACKGROUND: Only a small fraction of the information available is generally used in the majority of camera-based sensing approaches for vital sign monitoring. Dedicated skin pixels, for example, fall into this category while other regions are often disregarded early in the processing chain. METHODS: We look at a simple processing chain for imaging where a video stream is converted to several other streams to investigate whether other image regions should also be considered. These streams are generated by mapping spatio-temporal and -spectral features of video segments and, thus, compressing the information contained in several seconds of video and encoding these in a new image. Two typical scenarios are provided as examples to study the applicability of these maps: face videos in a laboratory setting and measurements of a baby in the neonatal intensive care unit. Each measurement consists of the synchronous recording of photoplethysmography imaging (PPGI) and infrared thermography (IRT). We report the results of a visual inspection of those maps, evaluate the root mean square (RMS) contrast of foreground and background regions, and use histogram intersections as a tool for similarity measurements. RESULTS: The maps allow us to distinguish visually between pulsatile foreground objects and an image background, which is found to be a noisy pattern. Distortions in the maps could be localized and the origin could be discovered. The IRT highlights subject contours for the heart frequency band, while silhouettes show strong signals in PPGI. Reflections and shadows were found to be sources of signals and distortions. We can testify advantages for the use of near-infrared light for PPGI. Furthermore, a difference in RMS contrast for pulsatile and non-pulsatile regions could be demonstrated. Histogram intersections allowed us to differentiate between the background and foreground. CONCLUSIONS: We introduced new maps for the two sensing modalities and presented an overview for three different wavelength ranges. The maps can be used as a tool for visualizing aspects of the dynamic information hidden in video streams without automation. We propose focusing on an indirect method to detect pulsatile regions by using the noisy background pattern characteristic, for example, based on the histogram approach introduced.


Asunto(s)
Procesamiento de Imagen Asistido por Computador , Rayos Infrarrojos , Fotopletismografía , Análisis Espacio-Temporal , Termografía , Frecuencia Cardíaca , Humanos , Grabación en Video
3.
Sensors (Basel) ; 20(21)2020 Oct 22.
Artículo en Inglés | MEDLINE | ID: mdl-33105767

RESUMEN

Laser-induced fluorescence (LIF) spectroscopy using dyes is frequently applied for characterization of liquids and two-phase flows. The technique is utilized e.g., for mixing studies, thermometry, or droplet sizing. One major application of the LIF technique combined with Mie-scattering is the planar measurement of droplet sizes in spray systems. However, its uncertainty is determined, among others, by varying dye concentration and temperature changes occurring during mixing and droplet evaporation. Systematic experimental investigations are necessary to determine the influence of dye enrichment effects on the LIF-signal of single droplets. For these investigations, the fluorescence dye Eosin-Y is dissolved in water and ethanol, which are typical solvents and working fluids in bio-medical applications and power engineering. A photo-physical characterization of the mixtures under various conditions was conducted using a spectrometric LIF setup and a micro cell. For ethanol, a small temperature dependency of the Eosin-Y LIF signal is observed up to 373 K. Photo-dissociation of Eosin-Y is negligible for solution in ethanol while it is distinct in water. The LIF signals of the single droplets are studied with an acoustic levitator. Effects of droplet evaporation, droplet deformation and varying dye concentration on the LIF-signal are studied. The single droplet measurements revealed a complex change of the fluorescence signal with reduced droplet size. This is due to droplet deformations leading to variations in the internal illumination field as well as dye enrichment during evaporation.

5.
Arch Gynecol Obstet ; 301(1): 129-135, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31883045

RESUMEN

PURPOSE: Estimating fetal weight using ultrasound measurements is an essential task in obstetrics departments. Most of the commonly used weight estimation formulas underestimate fetal weight when the actual birthweight exceeds 4000 g. Porter et al. published a specially designed formula in an attempt to improve detection rates for such macrosomic infants. In this study, we question the usefulness of the Porter formula in clinical practice and draw attention to some critical issues concerning the derivation of specialized formulas of this type. METHODS: A retrospective cohort study was carried out, including 4654 singleton pregnancies with a birthweight ≥ 3500 g, with ultrasound examinations performed within 14 days before delivery. Fetal weight estimations derived using the Porter and Hadlock formulas were compared. RESULTS: Of the macrosomic infants, 27.08% were identified by the Hadlock formula, with a false-positive rate of 4.60%. All macrosomic fetuses were detected using the Porter formula, with a false-positive rate of 100%; 99.96% of all weight estimations using the Porter formula fell within a range of 4300 g ± 10%. The Porter formula only provides macrosomic estimates. CONCLUSIONS: The Porter formula does not succeed in distinguishing macrosomic from normal-weight fetuses. High-risk fetuses with a birthweight ≥ 4500 g in particular are not detected more precisely than with the Hadlock formula. For these reasons, we believe that the Porter formula should not be used in clinical practice. Newly derived weight estimation formulas for macrosomic fetuses must not be based solely on a macrosomic data set.


Asunto(s)
Macrosomía Fetal/diagnóstico , Peso Fetal/fisiología , Ultrasonografía Prenatal/métodos , Femenino , Humanos , Embarazo , Estudios Retrospectivos
6.
Reprod Sci ; 26(7): 1013-1018, 2019 07.
Artículo en Inglés | MEDLINE | ID: mdl-30419800

RESUMEN

The role of three-dimensional power Doppler ultrasonography of the endometrium in assisted reproduction is still far from clear. In this retrospective cohort study, transvaginal three-dimensional power Doppler examinations were performed 30 min before frozen-thawed embryo transfer. After pregnancy tests, two cohorts were established: P (pregnant, n = 31) and NP (nonpregnant, n = 31). The study only included nullipara with no uterine abnormalities who were undergoing infertility treatment at the Department of Gynecology, Obstetrics and Gynecological Endocrinology, Kepler University Hospital, Linz, Austria. The main outcome measures were the vascularization flow index (VFI), flow index (FI), and vascularization index (VI) in the endometrium/subendometrium, assessed using Virtual Organ Computer-aided AnaLysis (VOCAL™), and the endometrial volume. A total of 62 patients were enrolled in the study, forming two cohorts (pregnant, P; nonpregnant, NP). There were no significant differences between the two cohorts with regard to demographic data, numbers of embryos transferred, or embryo grading, but there was a significant difference in endometrial volume (cohort P, 3.17 ± 0.84 mL; cohort NP, 2.36 ± 0.9 mL; P = 0.001) and the pregnancy rate rises with larger volume. No differences were observed in the vascularization parameters FI, VFI, and VI in the endometrium and subendometrium. In the cohort of pregnant patients, there were 26 (41.9%) live births, with 21 term deliveries (80.8%). The endometrial volume was larger in the cohort of pregnant patients. Measurements were performed 30 min before embryo transfer, and no differences were observed in vascularization parameters in the subendometrium and endometrium.


Asunto(s)
Criopreservación , Transferencia de Embrión , Endometrio/diagnóstico por imagen , Fertilización In Vitro , Infertilidad/terapia , Ultrasonografía Doppler , Adulto , Implantación del Embrión , Transferencia de Embrión/efectos adversos , Endometrio/fisiopatología , Femenino , Fertilidad , Fertilización In Vitro/efectos adversos , Humanos , Imagenología Tridimensional , Infertilidad/diagnóstico por imagen , Infertilidad/fisiopatología , Nacimiento Vivo , Valor Predictivo de las Pruebas , Embarazo , Índice de Embarazo , Estudios Retrospectivos , Factores de Tiempo , Resultado del Tratamiento
7.
Arch Gynecol Obstet ; 299(2): 345-351, 2019 02.
Artículo en Inglés | MEDLINE | ID: mdl-30460613

RESUMEN

PURPOSE: This study evaluated the extent to which migrant women participate in the mandatory oral glucose tolerance test (OGTT) for gestational diabetes mellitus (GDM) screening in Austria. METHODS: A retrospective data analysis was carried out of births at an obstetrics unit in a university hospital between January 2013 and December 2015. The inclusion criteria were singleton pregnancies, live births, birth weight ≥ 3500, and no preexisting diabetes mellitus. The patient's extramurally obtained OGTT values and history of GDM were checked. If the mother's country of birth was not Austria, the woman was classified as a migrant. Three groups were defined: group 1-women with normal OGTT; group 2-women with pathological OGTT; and group 3-women without OGTT or with an incomplete OGTT. MAIN OUTCOME MEASURES: Numbers of complete and incomplete OGTTs and rate of women with pathological OGTTs not treated in accordance with the guidelines among mothers born in Austria or migrants. The groups were compared using the t-test, chi-squared test, or Fisher's exact test. RESULTS: A total of 3293 births met the inclusion criteria, and 43.52% of all mothers were migrants; 16.8% of all women had pathological OGTT findings. Only 60.1% of the latter received treatment in accordance with the guidelines. The proportion of mothers born in Austria who did not have OGTTs, or only incomplete ones, was 5.4%. In the group of migrant women, the corresponding figure was 10.5% (P < 0.01). CONCLUSIONS: Migrant women have significantly lower rates of participation in GDM screening.


Asunto(s)
Diabetes Gestacional/diagnóstico , Participación del Paciente/estadística & datos numéricos , Adulto , Austria , Femenino , Humanos , Tamizaje Masivo , Embarazo , Estudios Retrospectivos , Migrantes
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 2713-2718, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31946455

RESUMEN

With the advent of sensitive and affordable cameras, classical contact-based photoplethysmography (PPG) could be enhanced to the spatial domain. Cost-efficient cameras are available in everyday items such as smartphones or computer webcams. The PPG signal, blood volume changes in the vascularity, can be measured remotely by using the camera as a 2-D-PPG detector. However, the evaluation of the extracted signals has mostly been limited to the pulse rate and sometimes the systolic amplitude. In this work, we motivate to generate images and video sequences based on features from the PPG waveform commonly not extracted via cameras. This is achieved by calculating the features for timeseries extracted from an evenly spaced grid of virtual PPG sensors. We briefly discuss the adaption of conventional PPG algorithms to camera-based PPG imaging (PPGI). The extracted parameters are associated with vessel properties and thus, mapping these to images could lead to enhanced vascular diagnostics. In this work, we test the feasibility of the mapping approach: we present the preliminary results gathered from the analysis of two videos of lab experiments with healthy subjects.


Asunto(s)
Fotopletismografía , Algoritmos , Volumen Sanguíneo , Frecuencia Cardíaca , Procesamiento de Señales Asistido por Computador
9.
Arch Gynecol Obstet ; 298(6): 1101-1106, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-30284620

RESUMEN

PURPOSE: Sonographic fetal weight (FW) estimation to detect macrosomic fetuses is an essential part of everyday routine work in obstetrics departments. Most of the commonly used weight estimation formulas underestimate FW when the actual birth weight (BW) exceeds 4000 g. One of the best-established weight estimation formulas is the Hadlock formula. In an effort to improve the detection rates of macrosomic infants, Hart et al. published a specially designed formula including maternal weight at booking. The usefulness of the Hart formula was tested. METHODS: Retrospective study of 3304 singleton pregnancies, birth weight ≥ 3500 g. The accuracy of the Hadlock and Hart formula were tested. A subgroup analysis examined the influence of the maternal weight. The Chi-squared test and one-way analysis of variation were carried out. For all analyses, p < 0.05 was considered statistically significant. RESULTS: The overall percentages of births falling within ± 5% and ± 10% of the BW using the Hadlock formula were 27% and 53%, respectively. Using the Hart formula, 24% and 54% were identified within these levels. With the Hart formula, 94% of all weight estimations fall within 4200 g ± 5% and nearly 100% fall within 4200 g ± 10%. CONCLUSIONS: Applying the Hart formula results in an overestimation of fetal weight in neonates with a birth weight < 4000 g and fails to identify high-risk fetuses. We, therefore, do not consider Hart's formula to be of clinical relevance.


Asunto(s)
Macrosomía Fetal/diagnóstico , Peso Fetal/fisiología , Ultrasonografía Prenatal/métodos , Adulto , Femenino , Macrosomía Fetal/patología , Humanos , Recién Nacido , Masculino , Embarazo , Estudios Retrospectivos
10.
BMC Musculoskelet Disord ; 19(1): 83, 2018 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-29544497

RESUMEN

BACKGROUND: Being at risk for malnutrition can be observed among hospitalized patients of all medical specialties. There are only few studies in arthroplasty dealing with defining and assessing malnutrition as such a potentially risk. This study aims to identify the risk for malnutrition following primary (pAP) and revision arthroplasty (rAP) (1) using non-invasive interview based assessment tools and to analyze effects on clinical outcome (2) and quality of life (3). METHODS: A consecutive series of hospitalized patients of a Department of Arthroplasty at a Level 1 Trauma Center in Western Europe was observed between June 2014 and June 2016. Patients were monitored for being at risk for malnutrition at hospital admission (T1) and 6 months post surgery (T2) by non-invasive interview based assessment tools (NRS 2002, SF-MNA, MNA). Adverse events, length of hospital stay and quality of life (HRQL, SF-36) were monitored. RESULTS: 351 (283 pAP/ 68 rAP) patients were included. At T1, 13.4% (47) / 23.9% (84) / 27.4% (96) and at T2 7.3% (18) / 17.1% (42) / 16.0% (39) of all patients were at risk for malnutrition regarding NRS/SF-MNA/MNA. Prevalence of malnutrition risk was higher in rAP (22.1-29.4%) compared to pAP (11.3-26.9%). Patients being at risk for malnutrition showed prolonged hospitalization (NRS 14.5 to 12.5, SF-MNA 13.7 to 12.4, MNA 13.9 to 12.3 days, p < 0.05), delayed mobilization (NRS 2.1 to 1.7, SF-MNA 1.8 to 1.7, MNA 1.9 to 1.7 days), lower values in HRQL and more adverse events. CONCLUSIONS: There is a moderate to high prevalence of risk for malnutrition in arthroplasty that can easily be assessed through interview based screening tools. Being at risk for malnutrition can reduce the clinical outcome following pAP and rAP. Patients with an impaired nutritional status show reduced values in physical and mental aspects of HRQL. Non-invasive interview-based nutritional assessment can predict adverse events in primary and revision total arthroplasty and can therefore help identifying patients at risk before surgery. TRIAL REGISTRATION: The study protocol was approved by the local ethics committee (193/2014BO2) and registered at the German Clinical Trials Register according to WHO standard ( DKRS00006192 ).


Asunto(s)
Artroplastia/efectos adversos , Desnutrición/diagnóstico , Evaluación Nutricional , Reoperación/efectos adversos , Adulto , Anciano , Anciano de 80 o más Años , Artroplastia/tendencias , Femenino , Estudios de Seguimiento , Humanos , Masculino , Desnutrición/epidemiología , Persona de Mediana Edad , Estado Nutricional/fisiología , Valor Predictivo de las Pruebas , Estudios Prospectivos , Reoperación/tendencias , Factores de Tiempo
11.
Eur J Health Econ ; 19(8): 1087-1110, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-29445942

RESUMEN

The present paper provides first empirical evidence on the relationship between market size and the number of firms in the healthcare industry for a transition economy. We estimate market-size thresholds required to support different numbers of suppliers (firms) for three occupations in the healthcare industry in a large number of distinct geographic markets in Slovakia, taking into account the spatial interaction between local markets. The empirical analysis is carried out for three time periods (1995, 2001 and 2010) which characterise different stages of the transition process. Our results suggest that the relationship between market size and the number of firms differs both across industries and across periods. In particular, we find that pharmacies, as the only completely liberalised market in our dataset, experience the largest change in competitive behaviour during the transition process. Furthermore, we find evidence for correlation in entry decisions across administrative borders, suggesting that future market analysis should aim to capture these regional effects.


Asunto(s)
Competencia Económica/organización & administración , Competencia Económica/tendencias , Sector de Atención de Salud/organización & administración , Sector de Atención de Salud/tendencias , Odontólogos/tendencias , Sector de Atención de Salud/economía , Humanos , Modelos Económicos , Farmacias/tendencias , Médicos/tendencias , Características de la Residencia , Eslovaquia , Factores Socioeconómicos , Análisis Espacial
12.
GMS J Med Educ ; 34(5): Doc67, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-29226235

RESUMEN

There is an absence of broad-based and binding curricular requirements for structured competency-based post-graduate medical training in Germany, and thus no basis for comparing the competencies of physicians undergoing training in a medical specialty (Ärzte im Weiterbildung). In response, the German Society of Primary Care Pediatrics' working group on post-graduate education (DGAAP) has identified realistic entrustable professional activities (EPAs) in primary care, defined their number, scope and content, selected competency domains, specified required knowledge and skills, and described appropriate assessment methods. These guidelines are referred to as PaedCompenda and can be accessed electronically by educators in pediatric medicine; the use and effectiveness of these guidelines are monitored by the German Association for Medical Education's committee on post-graduate education (GMA). Teaching and training in pediatric medicine should take EPAs into consideration. To accomplish this, phases dedicated to primary care should be integrated into formal medical specialty training. Primary care pediatrics must enhance the sites where such training takes place into learning environments that prepare physicians trainees and turn the practicing specialists into mentoring educators.


Asunto(s)
Curriculum , Pediatría/educación , Competencia Clínica , Educación de Postgrado en Medicina , Alemania , Atención Primaria de Salud
13.
Phys Rev E ; 94(4-1): 042124, 2016 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-27841546

RESUMEN

Grand-canonical fluctuations of Bose-Einstein condensates of light are accessible to state-of-the-art experiments [J. Schmitt et al., Phys. Rev. Lett. 112, 030401 (2014).PRLTAO0031-900710.1103/PhysRevLett.112.030401]. We phenomenologically describe these fluctuations by using the grand-canonical ensemble for a weakly interacting Bose gas at thermal equilibrium. For a two-dimensional harmonic trap, we use two models for which the canonical partition functions of the weakly interacting Bose gas are given by exact recurrence relations. We find that the grand-canonical condensate fluctuations for weakly interacting Bose gases vanish at zero temperature, thus behaving qualitatively similarly to an ideal gas in the canonical ensemble (or microcanonical ensemble) rather than the grand-canonical ensemble. For low but finite temperatures, the fluctuations remain considerably higher than for the canonical ensemble, as predicted by the ideal gas in the grand-canonical ensemble, thus clearly showing that we are not in a regime in which the ensembles are equivalent.

14.
Eur J Obstet Gynecol Reprod Biol ; 200: 89-93, 2016 May.
Artículo en Inglés | MEDLINE | ID: mdl-26995147

RESUMEN

OBJECTIVE: Only one phase III trial has been published to date on the efficacy and safety of misoprostol vaginal inserts for inducing labor. The aim of this study was to compare misoprostol inserts with dinoprostone inserts. STUDY DESIGN: This retrospective cohort study evaluated the reduction in time to vaginal delivery and delivery within 24h, in routine clinical work, in 119 labor inductions using a 200-µg misoprostol vaginal insert (Misodel(®); June-October 2014) in comparison with 124 inductions using a 10-mg dinoprostone insert (Propess(®); December 2013-April 2014). RESULTS: Vaginal delivery within 24h occurred in 77.3% (n=92) of the misoprostol cohort and 74.2% (n=92) of the dinoprostone cohort (P=0.654). Time from insert application to vaginal delivery (min) was 761.76 (±409.44, cohort M) versus 805.17 (±473.00, cohort D) (P=0.817). Cesarean delivery was performed in 10.1% (n=12) versus 10.5% (n=13) in the misoprostol and dinoprostone cohorts, respectively (P≥0.999). The modified Bishop scores were 2.0 versus 3.0 (P=0.001), mean body mass index (BMI) was 24.72 versus 23.95 (P=0.033), and fetal scalp blood testing was required in 12.6% (n=15) versus 3.2% (n=4; P=0.008). No differences were observed with regard to the rates of transfer to the neonatal unit or any type of fetal acidosis. CONCLUSIONS: The groups thus had similar results for rates of vaginal delivery within 24h, cesarean delivery and fetal outcomes. The misoprostol group had lower modified Bishop scores, higher BMIs, and a higher rate of fetal scalp blood testing.


Asunto(s)
Dinoprostona/administración & dosificación , Trabajo de Parto Inducido/métodos , Misoprostol/administración & dosificación , Oxitócicos , Administración Intravaginal , Adulto , Estudios de Cohortes , Femenino , Edad Gestacional , Humanos , Embarazo , Estudios Retrospectivos
15.
Disabil Rehabil Assist Technol ; 8(6): 482-95, 2013 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23350878

RESUMEN

PURPOSE: To present the AsTeRICS construction set, and examine different combinations of sensors installed in the platform and how users interact with them. METHOD: Nearly 50 participants from Austria, Poland and Spain were included in the study. They had a heterogeneous range of diagnoses, but as a common feature all of them experienced motor limitations in their upper limbs. The study included a 1 h session with each participant where the user interacted with a personalized combination of sensors, based on a previous assessment on their motor capabilities performed by healthcare professionals. The sensors worked as substitutes for a standard QWERTY keyboard and a standard mouse. Semi-structured interviews were conducted to obtain participants' opinions. All collected data were analyzed based on the qualitative methodology. RESULTS: The findings illustrated that AsTeRICS is a flexible platform whose sensors can adapt to different degrees of users' motor capabilities, thus facilitating in most cases the interaction of the participants with a common computer. CONCLUSION: AsTeRICS platform can improve the interaction between people with mobility limitations and computers. It can provide access to new technologies and become a promising tool that can be integrated in physical rehabilitation programs for people with motor disabilities in their upper limbs. IMPLICATIONS FOR REHABILITATION: The AsTeRICS platform offers an interesting tool to interface and support the computerized rehabilitation program of the patients. Due to AsTeRICS platform high usability features, family and rehabilitation professionals can learn how to use the AsTeRICS platform quickly fostering the key role of their involvement on patients' rehabilitation. AsTeRICS is a flexible, extendable, adaptable and affordable technology adapted for using computer, environmental control, mobile phone, rehabilitation programs and mechatronic systems. AsTeRICS makes possible an easy reconfiguration and integration of new functionalities, such as biofeedback rehabilitation, without major changes in the system.


Asunto(s)
Ataxia/rehabilitación , Evaluación de la Discapacidad , Personas con Discapacidad/rehabilitación , Actividad Motora/fisiología , Evaluación de Programas y Proyectos de Salud , Dispositivos de Autoayuda/tendencias , Interfaz Usuario-Computador , Adulto , Animales , Biorretroalimentación Psicológica , Diseño de Equipo , Femenino , Humanos , Masculino , Ratones , Persona de Mediana Edad , Extremidad Superior , Adulto Joven
16.
Phys Rev Lett ; 111(10): 100406, 2013 Sep 06.
Artículo en Inglés | MEDLINE | ID: mdl-25166639

RESUMEN

We investigate numerically the collisions of two distinguishable quantum matter-wave bright solitons in a one-dimensional harmonic trap. We show that such collisions can be used to generate mesoscopic Bell states that can reliably be distinguished from statistical mixtures. Calculation of the relevant s-wave scattering lengths predicts that such states could potentially be realized in quantum-degenerate mixtures of 85Rb and 133Cs. In addition to fully quantum simulations for two distinguishable two-particle solitons, we use a mean-field description supplemented by a stochastic treatment of quantum fluctuations in the soliton's center of mass: we demonstrate the validity of this approach by comparison to a mathematically rigorous effective potential treatment of the quantum many-particle problem.

17.
J Struct Biol ; 169(3): 286-93, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-19857575

RESUMEN

Methods for fine structural and functional analyses of complex and dynamic cell compartments must ensure high temporal resolution together with an excellent fine structural preservation. High-pressure freezing followed by freeze-substitution, and resin embedding is state of the art but its use is limited in combination with preembedding cytochemical techniques. Here we show a new approach for the exploration of compartments of the endocytosis system, which combines high-pressure freezing with peroxidase-catalyzed cytochemistry, thus using the potencies of both synergistically. Uptake of horseradish peroxidase-labeled molecules is followed by in vivo-staining and immobilization of endocytic compartments by generation of diaminobenzidine precipitates. Subsequently, the specimens are high pressure frozen, freeze-substituted, and embedded in resin. The excellent fine structural preservation, together with the high temporal resolution, and differentiating visualization of endocytic compartments qualify the new approach for morpho-functional studies of the complex and dynamic components of the endocytosis system involved in physiologic and pathologic cellular traffic, and in routes utilized in drug targeting strategies. The distinct appearances of membranes and reactive compartments provide optimal conditions for 3D-analyses by electron tomography allowing to discern subtle details of the complex 3D-structures of endocytic compartments.


Asunto(s)
Endocitosis/fisiología , Congelación , Histocitoquímica/métodos , Presión , Tomografía con Microscopio Electrónico , Aparato de Golgi/metabolismo , Células Hep G2 , Peroxidasa de Rábano Silvestre/metabolismo , Humanos
18.
Phys Rev Lett ; 102(1): 010403, 2009 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-19257172

RESUMEN

We investigate the scattering of a quantum matter wave soliton on a barrier in a one-dimensional geometry, and we show that it can lead to mesoscopic quantum superposition states, where the atomic gas is in a coherent superposition of being in the half-space to the left of the barrier and being in the half-space to the right of the barrier. We propose an interferometric method to reveal the coherent nature of this superposition, and we discuss in detail the experimental feasibility.

19.
Phys Rev Lett ; 100(14): 140408, 2008 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-18518013

RESUMEN

A Bose-Einstein condensate in a tilted double-well potential under the influence of time-periodic potential differences is investigated in the regime where the mean-field (Gross-Pitaevskii) dynamics become chaotic. For some parameters near stable regions, even averaging over several condensate oscillations does not remove the differences between mean-field and N-particle results. While introducing decoherence via piecewise deterministic processes reduces those differences, they are due to the emergence of mesoscopic entangled states in the chaotic regime.

20.
Phys Rev Lett ; 95(20): 200401, 2005 Nov 11.
Artículo en Inglés | MEDLINE | ID: mdl-16384037

RESUMEN

We study many-body tunneling of a small Bose-Einstein condensate in a periodically modulated, tilted double-well potential. Periodic modulation of the trapping potential leads to an analog of photon-assisted tunneling, with distinct signatures of the interparticle interaction visible in the amount of particles transferred from one well to the other. In particular, under experimentally accessible conditions there exist well-developed half-integer Shapiro-like resonances.

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