Adsorption of two pesticides on a clay surface: a theoretical study

The contamination of water resources with many organic xenobiotic compounds poses a challenge to environmental sciences and technologies [1]. Although in many cases these contaminants are present only in small concentrations, the large variety of such compounds (some of which are classified as priority pollutants) is a matter of concern. Adsorption, alone or as part of a more complex water or wastewater treatment process, has been seen as playing a very important role in the removal of many of these pollutants [2]. In this regard, the choice of adsorbent materials is crucial, which requires an understanding of the details involved in the adsorption of more or less complex organic molecules by a variety of surfaces of different types. In addition to laboratory studies, computational studies may be valuable in this study [3]. MCPA (2-methyl-4-chlorophenoxyacetic acid, a herbicide) and Clofibric acid (2-(4-chlorophenoxy)-2-methylpropanoic, the metabolite of a pharmaceutical, clofibrate, and also a herbicide) are two phenoxy acids that differ only slightly in their structures. However, a quite distinct behavior in adsorption phenomena on clay materials has been observed in past studies [4]. By relating those differences with the molecules' structural features through atomistic computational studies, some insight may be gained into the respective adsorption processes of this type of compounds. In the present work quantum chemical calculations at density functional theory level have been performed to study the adsorption of MCPA and Clofibric acid by a clay surface model. Since hydration plays an important role for the adsorption process of these species, solvent effects were considered by inclusion of water molecules explicitly into the quantum chemical calculations. The deprotonated negatively charged species were found to strongly interact with the surface and the distinct behavior of both species upon adsorption was compared with experimental evidences

Eficiência reprodutiva de porcas bísaras em regime ar livre, com maneio simplificado.

Eficiência reprodutiva de porcas bísaras em regime ar livre, com maneio simplificado.info:eu-repo/semantics/publishedVersio

Prefilter bandwidth effects in data symbol phase synchronizers of open loop

This work studies the effects of the prefilter bandwidth on the open loop symbol synchronizers. We consider three different prefilter bandwidth, namely, B1=¥ ( infinite), B2=2.tx and B3=1.tx, where tx is the transmission rate. We consider also four open loop symbol synchronizers, namely, the tank (tank), the SAW (SAW), the monostable (mon), and the astable (ast). The objective is to study the prefilter bandwidth with the four open loop symbol synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Prefilter bandwidth effects in sequential symbol synchronizers based on clock sampling by positive transitions

This work studies the effects of the prefilter bandwidth in the sequential symbol synchronizers based on clock sampling by positive transitions. The prefilter bandwidth B is switched between three values, namely B1=∞, B2=2. tx and B3=1. tx, where tx is the bit rate. The synchronizer has two variants, one discrete and other continuous. Each variant has two versions, one manual and other automatic. The objective is to study the prefilter bandwidth with the four synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Effects of the previous pulse shift and filter on the symbol synchronizer PLL

We will study the effects of the shift of the previous pulse temporal position (between P1 and P2) on the symbol synchronizers jitter behavior. Each pulse temporal position (P1 and P2), with the same previous filter, forms a group with four different carrier PLL (Phase Lock Loop) namely the analog, hybrid, combinational and sequential. The main objective is to study the synchronizers output jitter UIRMS (Unit Interval Root Mean Squared) as function of the input SNR (Signal to Noise Ratio)

Sequential symbol synchronizers based on pulse comparison operating by positive transitions at quarter rate

This work presents the sequential symbol synchronizer based on pulse comparison by positive transitions at quarter rate (txp/4). Their performance is compared with a reference synchronizer by both transitions at the rate (tx). For the reference and proposed synchronizer we consider two versions which are the manual (m) and the automatic (a). The objective is to study the four synchronizers and evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal Noise Ratio)

Sequential symbol synchronizers based on clock sampling by positive transitions

This work presents a sequential symbol synchronizer, that was discovered by us, and its functioning principle is based on the clock sampling by the input positive data transitions. This synchronizer has two topologies, namely the discrete and the continuous. Also, each topology has two versions which are the manual and the automatic. These synchronizers are very interesting, because the previous adjust of the manual version isn’t critical. The objective is to study the four synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Sequential symbol synchronizers based on pulse comparation at Half Rate

This work presents a synchronizer based on pulse comparation, between variable and fixed pulses. We consider four synchronizers, divided in two variants, one variant operate at the rate and the other at half rate. Each synchronizer variant has two versions which are the manual and the automatic. The objective is to study the synchronizers and evaluate the output jitter UIRMS (Unit Interval Root Mean Square) versus the input SNR (Signal Noise Ratio)

Effect of particle size distribution and dynamics on the performance of two-dimensional packing

AbstractExtensive computer simulation is used to revisit and to generalize two classical problems: (i) the random car-parking dynamics of A. Rényi and (ii) the irreversible random sequential adsorption (RSA) of parallel squares of same size on a planar substrate of area L2. In this paper, differently from the classical RSA, the squares obey the size distribution n(a)=n(1)a−τ, where a=1,2,3,… is the area of the squares. Using this scaling distribution and three classes of packing dynamics we study the final packing fraction of particles, ⊖(τ,L), and in particular its thermodynamic limit L→∞. We show that the efficiency to attain a high/low packing density of particles on the substrate is strongly dependent on the value of the exponent τ and on the characteristics of the dynamics

Synchronous and asynchronous sequential symbol synchronizers

In this work, we present two synchronizer groups: the synchronous and the asynchronous. The synchronous group is based in forward logic with flip flops and the asynchronous group is based in forward logic with delay line feedback. In each group we consider two versions: the manual and the automatic. The main objective is to study the two groups, each one with two versions and to observe its jitter performance as function of the noise