We explore the problem of two arbitrarily charged capacitors disposed in series with a resistor. It is well known that if their initial charges were zero, then the capacitors would behave physically as a single capacitor with capacitance given by a very usual formula. We consider the case for non-zero initial charges, where not only the formula breaks down, but also the idea of 'equivalent capacitor' is meaningless. Then, what kind of thing could be considered equivalent to two arbitrarily charged capacitors in series? In the present work, we answer that question and find that this equivalent thing is a capacitor together with a constant voltage source. This weird answer opens the possibility of two interpretations that seem to be in contradiction. We then solve this paradox showing that it is just an apparent ambiguity.

The susceptibility tests applied in the assays that investigate the potential of plant derivatives to be used as source of medicine against mycobacteria are often performed by using the broth microdilution method in microtiter plates. A quantitative interferometric method has been used to investigate the susceptibility of slowly growing mycobacteria. In the present article, this interferometric method is applied to rapidly growing mycobacteria. Samples of Mycobacterium smegmatis were exposed to methanol extract of fruits from Stifftia chrysantha and in this case, the interferometric method also complemented the conventional method by adding quantitative information.

ABSTRACT The permanent investigation of new antimycobacterial drugs is necessary for the eradication programs of tuberculosis and other mycobacterium-related diseases. The aim of the present study is to search for new sources of antimycobacterial drugs using plant materials. In this study, 11 plant materials (extracts, essential oils and some fractions) obtained from 4 species of medicinal plants traditionally used as general therapeutics for different illnesses and specifically as treatment of tuberculosis, were evaluated using the microplate resazurin assay against 2 species of the Mycobacterium tuberculosis Complex and 3 nontuberculous mycobacteria. The results showed the hexane extract and the essential oil from fruits of Pterodonemarginatus (Vogel) as potential sources of antimycobacterial drugs against 4 species of tested mycobacteria. The hexane fraction of methanol extract from leaves of Centella asiatica also presented significant mycobacterial growth inhibition, but against M. chelonae only. In conclusion, it was possible to contribute to the antimycobacterial investigations by presenting three new samples of plants with significant antimicrobial activity against four Mycobacteriumspp and suggest future studies about the antimycobacterial properties of fruits from P. emarginatus.

Interferometry was used together with the conventional microplate resazurin assay to evaluate the antimycobacterial properties of essential oil (EO) from fruits of Pterodon emarginatus and also of rifampicin against Mycobacterium bovis. The aim of this work is not only to investigate the potential antimycobacterial activity of this EO, but also to test the interferometric method in comparison with the conventional one. The Minimum Inhibitory Concentration (MIC) values of EO (625 μg/mL) and rifampicin (4 ng/mL) were firstly identified with the microplate method. These values were used as parameters in Drug Susceptibility Tests (DST) with interferometry. The interferometry confirmed the MIC value of EO identified with microplate and revealed a bacteriostatic behavior for this concentration. At 2500 μg/mL interferometry revealed bactericidal activity of the EO. Mycobacterial growth was detected with interferometry at 4 ng/mL of rifampicin and even at higher concentrations. One important difference is that the interferometric method preserves the sample, so that after weeks of quantitative observation, the sample can be used to evaluate the bactericidal activity of the tested drug.

The question whether the invariant speed c, Planck constant h/, and gravitational constant G can be or should be put equal to 1 is analyzed. The discussion is based on fundamental considerations concerning the notion of physical quantity. It is found that the issue is not a matter of appropriate unit selection. Further it is shown that classical space-time geometry and quantum mechanics can be formulated in such a way that the invariant speed and the action quantum are truly one and do not have to be set equal to one.

The anti-inflammatory and apoptotic activity of the essential oil of Syzygium cumini (L.) Skeels, Myrtaceae, leaves was investigated in vivo. The anti-inflammatory action and chronic granulomatous inflammation in BALB/c mice, intravenously infected with Mycobacterium bovis, BCG, (Bacillo Calmet Guerim), was judged by measuring and classifying the granulomas formed in the hepatic parenchyma. The degree of apoptosis in the inflammatory cells was also measured. A reduction in the granulomatous area and a change in the pattern of the granulomas were found. Anti-mycobacterial activity of the essential oil against M. bovis was detected in vitro by an interferometric method in liquid culture medium. The chemical constituents of the essential oil were determined by GC/MS. Higher yields of the essential oil of S. cumini leaves were obtained by extraction in a Clevenger apparatus when the fresh leaves were previously frozen as a pre-processing step. The essential oil obtained from this plant demonstrated a statistically significant and dramatic effect in the chosen model system.

It is demonstrated that the efficiency of antibiotics can be tested using an interferometric method. Two antibiotics were used as models to show that an interferometric method to monitor the metabolic activity of slowly growing bacteria can be a safer method to judge antimicrobial properties of substances than conventional methods. The susceptibility of Mycobacterium bovis to hexane extract of Pterodon emarginatus and to the well-known antibiotic rifampicin was tested with the interferometric method and with the conventional microplate method. The microplate method revealed a potential activity of hexane extract against M. bovis. However, the interferometric method showed that the action of this substance is rather limited. Also in the case of rifampicin, the interferometric method was able to detect resistant bacteria.

Leishmaniasis is an infection of viscera or tegument caused by protozoa Leishmania sp. The extensive period required for the treatment, which involves the use of toxic medicines, leads patients to drop treatment increasing the development of resistant forms of Leishmania sp. Lantana camara L., Verbenaceae, is a tropical plant native from America. Folk uses have been described for treatment of tumors, tetanus, rheumatism and malaria. This study evaluates the leishmanicidal activity of the essential oil of leaves from L. camara on promastigote forms of Leishmania chagasi and L. amazonensis and its toxic effects on Artemia salina (brine shrimp test), macrophage cultures and BALB/c mice. The chemical composition was evaluated using the gas chromatography coupled with mass spectrometer (GC-MS). Thirty substances, mostly mono and sesquiterpenes were identified. The most representative constituents were: germacrene D (24.90%), farnesene derivatives (22%) and (E)-cariophylene (14.31%). Bioassays revealed a significant leishmanicidal activity of essential oil against L. amazonensis (IC50 0.25 mu g/mL) and a potential toxic effect on Brine shrimp (LC50 10 mu g/mL) and macrophage assays (CC50 4 mu g/mL), while there was no toxic manifestation on mice. The data show the relevant potential of L. camara as a source of medicine for leishmaniasis treatment.

The influence of electric fields on the velocity of the chemical reaction 4HF+SiO2→SiF4+2H2O in aqueous solution is investigated experimentally. The field strengths used were high enough to measure nonlinear effects. The results permit a critical analysis of a theoretical model known in literature. The basic idea of dipole orientation changing the rate of the primary step of the chemical reaction can explain the experimental data, but several important details of the original model had to be changed. The primary step involves two hydrogen fluoride (HF) molecules rather than one, and field screening by mobile ions has a significant influence causing nonlinear effects. The fact that field screening plays an important role implies that electric field-assisted HF etching of silica may by used as an instrument for measuring ion concentrations in highly concentrated electrolytes. The data measured may be well described by a theoretical model based on mean field approximations. The results give an insight into the structure of highly concentrated hydrofluoric acid and also permit a critical analysis of applications of the effect in measuring electric fields written in glass samples by electrothermal poling. The effect may also be used for shaping glass surfaces.

An interferometer that measures the refractive index changes due to bacterial metabolism is described. The apparatus permits simultaneous and real time measurement of bacterial growth in several samples of slowly growing mycobacteria. The error sources are discussed and the sensitivity of the apparatus is tested. For the species Mycobacterium bovis BCG and M. smegmatis, a relation between refractive index change and bacterial concentration is determined experimentally and the time constant of bacterial growth is measured.

It is shown that the l 1-distance in the space of probability assignments on a finite set Ω provides a criterion to judge whether two assignments are too close to each other to be distinguished by a statistical test. The criterion is independent of the number of elements of Ω. Other notions of distance are also discussed.

The width of the depletion region in fused-silica samples thermally poled during various periods of time is investigated experimentally with four previously reported characterization techniques in an attempt to unify their findings. Although all measurements give a similar width of the depletion region, it is shown that the determination of the profile of chi(2) is also required for a good estimate of the nonlinearity induced by poling.

Evidence is given that Renyi entropies of macroscopic thermodynamic systems defined on the bases of probabilities of microstates cannot be related to observables. The notion of observable is clarified.

The metabolic activity of Bacilo Calmette-Guerin (BCG) was observed monitoring small changes of t he refractive index of t he nutrient solution interferometrically. Two samples were ke pt i n adjacent compartments of a stainless s teel sample holder, which was equipped with op tical windows. One sample c ontained 2.5 ml of t he nutrient solution (Bacto Middlebrook 7H9 Broth with ADC Enrichment) and 4x10 6 bacteria BCG. The other one, which was used as a reference, contained only the nutrient solution. The sample holder was put between the mirrors of a FabryPerot t ype interferometer. The light source used was a po larized He-Ne laser and the primary laser beam was s plit into two pa rallel beams to p rovide simultaneous measurements of both samples. The temperature of the sample holder and interferometer was computer controlled with precision of e few mK. A temperature scan technique was used to resolve interference fringes with a resolution better than 3% of a fringe. This, in terms of index change, corresponds to a resolution of 2x10 -7 . The interferometer is stable during weeks. In the present work results of new measurements are presented and a new kind of interferometer, which is being built, is described, were the temperature controlled phase scan is substituted by a spatial phase scan. This technique permits even h igher phase resolution and reduces the time of data analysis considerably. Observation of bacterial activity is used to determine susceptibility of bacteria against antibiotics. The c onventional way uses cultures on solid substrates and is extremely time c onsuming, which can be prohibitive in certain cases. There exists a method to observe bacterial activity in real time that uses 14 C labeled nutrients (BACTEC 460TB). However, this method is so expensive that its use is r estricted to very few research laboratories. The interferometric technique is a low cost alternative to the radioactive method.

The electric field recorded in silica samples thermally poled during various intervals was measured by etching. The field is nearly uniform and increases to a maximum (∼3.6×108 V/m) in few minutes of poling and subsequently decreases slowly toward a steady level (∼1.4×108 V/m). The depletion layer becomes neutral even before the field reaches steady state. An upper limit of (0.7±0.2) μm was found for the thickness of the negatively charged edge of the depletion region. The value of χ(3) is the same for all poling times.

It is shown that bacterial activity, even of slowly growing species, can be detected by precise interferometric measurements of refractive index changes of the culture medium. The bacteria-containing sample is kept in an isothermal block together with a reference liquid without bacteria. The biological activity is obtained from the difference of the index changes of these samples. Experiments were performed with Bacilo Calmette-Guérin. The order of magnitude of the observed total refractive index change was compatible with theoretical estimates based on the amount of available oxygen. An unexpected positive index change during the lag phase was observed, which might permit fast diagnostics in medical applications. This technique may provide cheap and quick tests of bacterial susceptibility with respect to antibiotics.

Four characterization techniques are compared in the measurement of the depletion region of silica poled during different time intervals. The effect of pre-etching the samples prior to poling is also investigated.

We developed a simple interferometric method to measure the refractive index of transparent liquids with precision of the order of 10 -6 . The main sources of error are analyzed and techniques to minimize these errors are described. A simple way of temperature stabilization of the sample is described. Some measurements of refractive index were performed to test the equipment.

The time evolution of the recorded electric field and the width of the depletion layer are estimated in thermally poled silica. The predicted second harmonic is compared with the signal measured in real time.