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Ultra-short pulsed laser ablation may be used for high-precision machining with very low thermal influence on the processed materials. Due to this reason, lasers are increasingly used for processing of advanced materials, such as titanium alloys, nickel-based alloys or steel, every year. In this study, four advanced technical materials were analysed and compared under femtosecond laser irradiation with three different wavelengths. The main laser-material interaction parameters were identified, namely the ablation threshold and removal efficiency parameters. Higher removal rates were found for Ti6Al4V alloy with all three harmonic wavelengths. To increase process productivity, a method of increasing the repetition rate and scanning speed was presented. With the maximum repetition rate, the productivity increased five-fold with a similar removed depth and surface quality. Finally, the suitability of the identified parameters with regard to quality and productivity was demonstrated for fabrication of two complex structures – honeycomb and dot – which has the potential to improve friction properties of advanced materials.

Selecting the proper cutting conditions for milling parts is one of the most important tasks in setting up manufacturing to achieve minimum machining times and to ensure the desired tool life. This is particularly important when machining parts made of difficult-to-cut materials. However, if the required technological conditions are not achieved due to the shape of the toolpath itself, even the conventional setting of the technological conditions will not help achieve the optimum result. It is therefore essential to ensure that the technological conditions are achieved directly at the contact point between the tool and the workpiece, which is often forgotten in automatic toolpath preparation. This paper therefore presents a specific solution for optimizing the feed rate right at the contact point between the workpiece and the tool to maintain a constant feed per tooth. The work contributes to the investigation of the relationship between the tool diameter and the shape of the machined surface when a constant feed per tooth is required as well. The achievement of feed rate is performed by tests on the machine tool and the benefits of using the optimization of feed rate are further discussed.

From significant Czech migration to Bulgaria in the late 19th century, Czech teachers were the largest vocational group. The late 19th century was also one of the epoch-making periods of Bulgarian history when the system of secondary and grammar schools has been formed along with other institutions. On one hand this situation created a possibility for work of foreign teachers, but on the other hand local schools faced many problems. One of most perceptible ones was shortage of proper textbooks. Some Czech teachers were involved in this important publishing activity. In this paper I briefly present general situation of Bulgarian education system of the period, summarize information about Bulgarian textbooks written by Czechs, and introduce several Czech writers.

Abstract Birefringent microspheres, trapped in vacuum and set into rotation by circularly polarised light, demonstrate remarkably stable translational motion. This is in marked contrast to isotropic particles in similar conditions. Here we demonstrate that this stability is obtained because the fast rotation of these birefringent spheres reduces the effect of azimuthal spin forces created by the inhomogeneous optical spin of circularly polarised light. At reduced pressures, the unique profile of these rotationally averaged, effective azimuthal forces results in the formation of nano-scale limit cycles. We demonstrate feedback cooling of these non-equilibrium oscillators, resulting in effective temperatures on the order of a milliKelvin. The principles we elaborate here can inform the design of high-stability rotors carrying enhanced centripetal loads or result in more efficient cooling schemes for autonomous limit cycle oscillations. Ultimately, this latter development could provide experimental access to non-equilibrium quantum effects within the mesoscopic regime.

Abstract We explore, experimentally and theoretically, the emergence of coherent coupled oscillations and synchronization between a pair of non-Hermitian, stochastic, opto-mechanical oscillators, levitated in vacuum. Each oscillator consists of a polystyrene microsphere trapped in a circularly polarized, counter-propagating Gaussian laser beam. Non-conservative, azimuthal forces, deriving from inhomogeneous optical spin, push the micro-particles out of thermodynamic equilibrium. For modest optical powers each particle shows a tendency towards orbital circulation. Initially, their stochastic motion is weakly correlated. As the power is increased, the tendency towards orbital circulation strengthens and the motion of the particles becomes highly correlated. Eventually, centripetal forces overcome optical gradient forces and the oscillators undergo a collective Hopf bifurcation. For laser powers exceeding this threshold, a pair of limit cycles appear, which synchronize due to weak optical and hydrodynamic interactions. In principle, arrays of such Non-Hermitian elements can be arranged, paving the way for opto-mechanical topological materials or, possibly, classical time crystals. In addition, the preparation of synchronized states in levitated optomechanics could lead to new and robust sensors or alternative routes to the entanglement of macroscopic objects.

ABSTRACT The search for the “Holy Grail” in clinical diagnostic microbiology—a reliable, accurate, low-cost, real-time, easy-to-use method—has brought up several methods with the potential to meet these criteria. One is Raman spectroscopy, an optical, nondestructive method based on the inelastic scattering of monochromatic light. The current study focuses on the possible use of Raman spectroscopy for identifying microbes causing severe, often life-threatening bloodstream infections. We included 305 microbial strains of 28 species acting as causative agents of bloodstream infections. Raman spectroscopy identified the strains from grown colonies, with 2.8% and 7% incorrectly identified strains using the support vector machine algorithm based on centered and uncentred principal-component analyses, respectively. We combined Raman spectroscopy with optical tweezers to speed up the process and captured and analyzed microbes directly from spiked human serum. The pilot study suggests that it is possible to capture individual microbial cells from human serum and characterize them by Raman spectroscopy with notable differences among different species. IMPORTANCE Bloodstream infections are among the most common causes of hospitalizations and are often life-threatening. To establish an effective therapy for a patient, the timely identification of the causative agent and characterization of its antimicrobial susceptibility and resistance profiles are essential. Therefore, our multidisciplinary team of microbiologists and physicists presents a method that reliably, rapidly, and inexpensively identifies pathogens causing bloodstream infections—Raman spectroscopy. We believe that it might become a valuable diagnostic tool in the future. Combined with optical trapping, it offers a new approach where the microorganisms are individually trapped in a noncontact way by optical tweezers and investigated by Raman spectroscopy directly in a liquid sample. Together with the automatic processing of measured Raman spectra and comparison with a database of microorganisms, it makes the whole identification process almost real time.

Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects, ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in the life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nano-particle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration.

Efficient separation and sensitive identification of pathogenic bacterial strains is essential for a prosperous modern society, with direct applications in medical diagnostics, drug discovery, biodefense, and food safety. We developed a fast and reliable method for antibody-based selective immobilization of bacteria from suspension onto a gold-plated glass surface, followed by detection using strain-specific antibodies linked to gold nanoparticles decorated with a reporter molecule. The reporter molecules are subsequently detected by surface-enhanced Raman spectroscopy (SERS). Such a multi-functionalized nanoparticle is called a SERS-tag. The presented procedure uses widely accessible and cheap materials for manufacturing and functionalization of the nanoparticles and the immobilization surfaces. Here, we exemplify the use of the produced SERS-tags for sensitive single-cell detection of opportunistic pathogen Escherichia coli, and we demonstrate the selectivity of our method using two other bacterial strains, Staphylococcus aureus and Serratia marcescens, as negative controls. We believe that the described approach has a potential to inspire the development of novel medical diagnostic tools for rapid identification of bacterial pathogens.

Widely used classical angiography with the use of iodine contrast agents is highly problematic, particularly in patients with diabetes mellitus, cardiac and pulmonary diseases, or degree III or IV renal insufficiency. Some patients may be susceptible to allergic reaction to the iodine contrast substance. The intravenous injection of a bolus of CO2 (negative contrast) is an alternative method, which is, however, currently only used for imaging blood vessels of the lower limbs. The aim of our project was to design and test on an animal model a methodology for injecting the CO2 foam which would minimize the possibility of embolization of the brain tissue and heart infarction, leading to their damage. This is important research for the further promotion of the use of CO2, which is increasingly important for endovascular diagnosis and treatment, because carbon-dioxide-related complications are extremely rare. CO2 foam was prepared by the rapid mixing in a 2:1 ratio of CO2 and fetal bovine serum (FBS)-enriched Dulbecco’s Modified Eagle Medium (DMEM). Freshly prepared CO2 foam was administered into the catheterized rat tail vein or cannulated rat abdominal aorta and inferior vena cava (IVC). CO2 foam was compared with commercially available microbubbles (lipid shell/gas core). The rat heart in its parasternal long axis was imaged in B-Mode and Non-linear Contrast Mode before/during and after the contrast administration. Samples of the brain, heart and lungs were collected and subjected to histological examination. The non-linear contrast imaging method enables the imaging of micron-sized gas microbubbles inside a rat heart. The significantly shorter lifetime of the prepared CO2 foam is a benefit for avoiding the local ischemia of tissues.

Abstract The ever‐growing field of microfluidics requires precise and flexible control over fluid flows at reduced scales. Current constraints demand a variety of controllable components to carry out several operations inside microchambers and microreactors. In this context, brand‐new nanophotonic approaches can significantly enhance existing capabilities providing unique functionalities via finely tuned light−matter interactions. A concept is proposed, featuring dual on‐chip functionality: boosted optically driven diffusion and nanoparticle sorting. High‐index dielectric nanoantennae is specially designed to ensure strongly enhanced spin−orbit angular momentum transfer from a laser beam to the scattered field. Hence, subwavelength optical nanovortices emerge driving spiral motion of plasmonic nanoparticles via the interplay between curl−spin optical forces and radiation pressure. The nanovortex size is an order of magnitude smaller than that provided by conventional beam‐based approaches. The nanoparticles mediate nanoconfined fluid motion enabling moving‐part‐free nanomixing inside a microchamber. Moreover, exploiting the nontrivial size dependence of the curled optical forces makes it possible to achieve precise nanoscale sorting of gold nanoparticles, demanded for on‐chip separation and filtering. Altogether, a versatile platform is introduced for further miniaturization of moving‐part‐free, optically driven microfluidic chips for fast chemical analysis, emulsion preparation, or chemical gradient generation with light‐controlled navigation of nanoparticles, viruses or biomolecules.

The interferometric acquisition of the transmission matrix (TM) of a multimode optical fibre (MMF), which is at the heart of multimode fibre-based endoscopic imaging methods, requires using a reference beam. Attempts to use an internal reference, that is to provide the reference in a common pathway geometry through the MMF itself, lead to a speckled reference intensity and consequential occurrence of “blind spots”—locations where insufficient optical power in the reference wave inflicts strong measurement errors. Here we show that combining a relatively small number of TMs, which are measured using different internal references, facilitates a complete elimination of blind spots, and thereby a significant enhancement of the imaging quality.

The climate change and growing production of crops increase the demand for the water and the efficient use of water in agriculture becomes more critical. This experiment presents the results of research in the orchard with different irrigation programs and fertigation on yield and quality parameters of the ’Gala‘ and ’Fuji‘ apple tree. Three irrigation programs were applied IR + F – full irrigation with fertigation; IR – full irrigation without fertigation; NON‑IR – non‑irrigation, only natural precipitations. There were no differences observed among these three irrigation programs for tree diameter, sugar content, starch content and fruits firmness (P < 0.05). Significant deficit of water was in program IR and NON‑IR, at the length of annual growth, where the reduction was from from 680 mm to 440 mm at the ‘GALA’ variety. Statistically important differences between the irrigation variants were found out at the variety ‘Fuji’, in parametres yield, fruit weight and fruit diameter. Between programs IR + F and NON‑IR was the difference of fruit weight 25.6 g (14.3 %) and of fruit diameter 4.5 mm (5.8 %).

ABSTRACT Recent technological progress in a precise control of optically trapped objects allows much broader ventures to unexplored territory of thermal motion in non-linear potentials. In this work, we exploit an experimental set-up of holographic optical tweezers to experimentally investigate Brownian motion of a micro-particle near the inflection point of the cubic optical potential. We present two complementary views on the non-linear Brownian motion. On an ensemble of stochastic trajectories, we simultaneously determine (i) the detailed short-time position statistics and (ii) the long-distance first-passage time statistics. We evaluate specific statistical moment ratios demonstrating strongly non-linear stochastic dynamics. This is a crucial step towards a possible massive exploitation of the broad class of complex non-linear stochastic effects with objects of more complex structure and shape including living ones.

Selenium (Se) is an element with many commercial applications as well as an essential micronutrient. Dietary Se has antioxidant properties and it is known to play a role in cancer prevention. However, the general population often suffers from Se deficiency. Green algae, such as Chlorella vulgaris, cultivated in Se-enriched environment may be used as a food supplement to provide adequate levels of Se. We used Raman microspectroscopy (RS) for fast, reliable, and non-destructive measurement of Se concentration in living algal cells. We employed inductively coupled plasma-mass spectrometry as a reference method to RS and we found a substantial correlation between the Raman signal intensity at 252 cm−1 and total Se concentration in the studied cells. We used RS to assess the uptake of Se by living and inactivated algae and demonstrated the necessity of active cellular transport for Se accumulation. Additionally, we observed the intracellular Se being transformed into an insoluble elemental form, which we further supported by the energy-dispersive X-ray spectroscopy imaging.

Raman spectroscopy has a broad range of applications across numerous scientific fields, including microbiology. Our work here monitors the influence of culture media on the Raman spectra of clinically important microorganisms (Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans). Choosing an adequate medium may enhance the reproducibility of the method as well as simplifying the data processing and the evaluation. We tested four different media per organism depending on the nutritional requirements and clinical usage directly on a Petri dish. Some of the media have a significant influence on the microbial fingerprint (Roosvelt-Park Institute Medium, CHROMagar) and should not be used for the acquisition of Raman spectra. It was found that the most suitable medium for microbiological experiments regarding these organisms was Mueller-Hinton agar.

The most important sources of biomass energy are currently coming from agricultural activity. A sizeable portion in production areas is waste wood after the winter cut of orchards and vineyards, which cover areas exceeding 30,000 ha in the Czech Republic. The most important are species like apples, peaches, apricots, plums, sweet cherries, sour cherries and grapevines. Average production of wood mass for individual species of fruit trees and grapevines ranges from 1,540 kg/ha up to 6,762 kg/ha, i.e. 1.5 t/ha to 6.8 t/ha. The calorific value for these species ranges from 14.70 to 16.39 MJ/kg, with moisture between 6 and 8%. The results show that the total measured energy potential of the fruit species-cultivated areas is 1,469.7 TJ for the whole Czech Republic.

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent developments in the analysis of algal biomass with the main focus on the Laser-Induced Breakdown Spectroscopy, Raman spectroscopy, and partly Laser-Ablation Inductively Coupled Plasma techniques. The advantages of the selected laser-based analytical techniques are revealed and their fields of use are discussed in detail.

Antibiotics cure infections by influencing bacterial growth or viability. Antibiotics can be divided to two groups on the basis of their effect on microbial cells through two main mechanisms, which are either bactericidal or bacteriostatic. Bactericidal antibiotics kill the bacteria and bacteriostatic antibiotics suppress the growth of bacteria (keep them in the stationary phase of growth). One of many factors to predict a favorable clinical outcome of the potential action of antimicrobial chemicals may be provided using in vitro bactericidal/bacteriostatic data (e.g., minimum inhibitory concentrations—MICs). Consequently, MICs are used in clinical situations mainly to confirm resistance, and to determine the in vitro activities of new antimicrobials. We report on the combination of data obtained from MICs with information on microorganisms’ “fingerprint” (e.g., DNA/RNA, and proteins) provided by Raman spectroscopy. Thus, we could follow mechanisms of the bacteriostatic versus bactericidal action simply by detecting the Raman bands corresponding to DNA. The Raman spectra of Staphylococcus epidermidis treated with clindamycin (a bacteriostatic agent) indeed show little effect on DNA which is in contrast with the action of ciprofloxacin (a bactericidal agent), where the Raman spectra show a decrease in strength of the signal assigned to DNA, suggesting DNA fragmentation.

This paper is focused on procedure proposal for implementation of technologies for utilization of waste vine cane from vineyards for the energy purposes, including an assessment of their effectiveness. Evaluated were three variants of technological. Evaluated were 3 variants of technological procedures with using the shredder with discharge spout, shredder with container and the vine cane baler. For the individual variants were modeled operating costs, depending on the extent of the annual use that reflects the size of the vineyard. The operating costs were also confronted with the price of wood chips. The results show a clear recommendations of these technologies for vineticultural businesses with area of vineyards with more than 30–40 ha.

Application of higher doses of compost has several technical problems at the same time. Compost application at higher doses required relatively high consumption of working time deployed machinery. That is mainly affected loading capacity of the spreaders. Standard is a spreader with a loading capacity of 5–10 t, for higher capacity it is necessary to monitor the influence of the chassis to a higher soil compaction, especially in wheel tracks. This paper deals with determination of the cost of application for spreading compost at high doses 60–100 t.ha−1. From the proven data of performance, acquisition costs of machinery and fuel consumption were determined hectare costs for the spreader of carrying capacity 5, 8, 10 a 15 t and transport distances corresponding to an area of 8–100 hectares of fertilized land. Costs were determined by using the program AGROTEKIS, by using the database machines, manufacturers data and other available data, direct measurements and related experiments. Application costs for the dose 60 t.ha−1 are 2 100–5 250 CZK.ha−1, for the dose 80 t.ha−1 are 2 750–7 000 CZK.ha−1and for the dose 100 t.ha−1 are 2 650–8 650 CZK.ha−1. The results are useful for quick and easy calculation of costs for fertilizing with higher doses of compost and deciding on the selection of used spreader.

This paper deals with monitoring of changes in soil compaction at two experimental sites (Lednice and Valtice) in the alleyway of vineyards. The experimental measurements were carried out during the period 2009–2011. Penetration resistance of the soil was measured using the penetrometer (type PN 10) to a depth up to 520 mm. The measurements were carried out alternatively in variants with grassed and cultivated alleyways of vineyards. The samples were performed in the wheeltracks and in the middle of an alleyway. The control samples were performed between the plants in the row. The results show that the penetration resistance reaches lower values on the grassed alleyway. At both variants is obvious increase of the penetration resistance above the critical value already in a depth of 0.2 m. From the annual comparison of the penetration resistance it is clear the higher increase in the third year.

There is registered approximately 18 000 ha of intensive vineyards in this time in Czech Republic. The intensive viticulture production is represented by high amount of working operations which are practised by using of mechanization. Frequency of passages by mechanization in interrow of descent is different by single variants of production processes. Their currently number varies about 20–25 per season. The soil compression is the highest in wheels tracked lines and middle of the interrow. If the compaction reaches over the critical limit, it can be this state escorted by weighty incidence (decrease of decree, increasing by power severity by soil cultivation and other). These contributions deal with analysis of soil compression in different areas in the region of the South Moravia. The used methods were undisturbed sample and penetration resistance with using of penetrometer.

The experiment was focused on evaluation of influence of compost application on soil water retention. Soil retention is a major soil water property that governs soil functioning as a ecosystem. Soil moisture forms a major buffer against flooding, and water capacity in subsoil is a major factor for plant growth. The effects of changes in soil water retention depend on the proportions of the textural components and the amount of organic carbon present in the soil. During seasons of 2009 and 2010, experiments at two sites of different soil conditions prepared by addition of compost doses of 50 and 100 t.ha−1 were carried out. Changes of humidity were continuously monitored and recorded by soil moisture sensors. Results showed that application of compost of above mentioned doses positively affected water retention of the soil. Organic matter, applied at the above mentioned amount has a positive effect on soil moisture retention, regardless of possible influence of soil type, grassing and amount of rainfalls. Outcomes of experiment become bases for recommended compost doses as well as for technical proposal of compost application processes.