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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Modification of bis(ditertiarybutylphosphinomethyl)benzene for improved catalyst separation and stability

Parnham, Benjamin L. January 2007 (has links)
Palladium complexes of bis(di-tert-butylphosphinomethyl)benzene (DTBPMB) show remarkably high activity as alkene methoxycarbonylation catalysts, in addition to numerous other catalytic conversions, and are currently being commercialised by Lucite in ethene methoxycarbonylation to methyl propanoate. Any large-scale exploitation of this catalyst system for heavier products, however, is likely to be hindered by catalyst-product separation problems common to homogeneous catalysts; hence modification of this catalyst system to allow facile product separation was investigated. Tethering of DTBPMB residues onto polystyrene via Suzuki-type coupling of suitable precursors onto bromopolystyrene and boronic acid functionalised polystyrene resins was investigated and the phosphine was successfully immobilised. Phosphination of the resins was not complete however and as such there is concern that other phosphine residues may be present which do not exhibit a bidentate binding motif. The synthesis of a potassium sulfonate derivative of DTBPMB (KBPMBS) was successful and immobilisation of this onto ion exchange resins was also investigated. Some preliminary results from studies into 1-octene methoxycarbonylation using palladium complexes of these resins were obtained. Supporting of this diphosphine onto silica via a sol-gel co-condensation methodology was also investigated; the synthesis of a suitably functionalised precursor containing a sulfonamide linkage was successful via protection of the diphosphine using borane. Although formation of the silica support was successful, attempts to deprotect the phosphine-borane resulted in cleavage of the ligand from the support. An alternative route to this supported ligand was attempted and others discussed. Synthesis of a suitable sol-gel precursor via alkene hydrosilation was also attempted and is discussed. Supporting of the sulfonated phosphine, KBPMBS onto silica functionalised with imidazolium tethered residues was also investigated, although complete leaching of the phosphine from the support by methanol washing was observed. Immobilisation of the synthesised KBPMBS ligand in an ionic liquid (IL) phase was investigated. Complex formation and catalytic activity were demonstrated and a positive effect on conversion was observed upon addition of carbon dioxide to the system; possibly due to the increased CO solubility within the IL phase. Efficient product separation from the IL-immobilised catalyst system was demonstrated, both by organic extraction and using supercritical carbon dioxide flow. However, poor catalyst stability under these conditions appears to present a barrier to recycling this system, with loss of conversion observed on catalyst recycling. Other attempts to immobilise the DTBPMB ligand are discussed and reduction of the sulfide derivative of DTBPMB was demonstrated using hexachlorodisilane, which could be used as a general synthetic strategy for protecting highly electron rich phosphines. It is possible that increasing the bulk of the DTBPMB ligand may increase catalyst stability and result in catalyst systems with higher turnover numbers. Therefore syntheses of bulky ligands based on the DTBPMB backbone were investigated. 1,2,4,5-tetrakis(di(tert-butyl)phosphinomethyl)benzene was successfully synthesised although palladium complexes of this showed no activity in catalytic methoxycarbonylation. Attempts to synthesise a related biphenyl-based tetraphosphine is also discussed, although isolation of this in a pure form was not achieved. Routes toward tetraphenyl and dimethyl-diphenyl functionalised derivatives of DTBPMB have also been explored, although only a monophosphine was isolated due to difficulties in obtaining an intermediate di(chloromethyl) precursor in both synthetic pathways, although this now appears to have been overcome.
92

Phosphine modified rhodium catalysts for the carbonylation of methanol

Lamb, Gareth W. January 2008 (has links)
The carbonylation of methanol to acetic acid is one of the most important applications in homogeneous catalysis. The first chapter comprises a review on the mechanistic studies into the catalytic cycle of the ‘Monsanto process’ and includes some of the most prominent studies into the use of phosphines in the rhodium-catalysed carbonylation of methanol. The second chapter of this thesis reports on an investigation into the application of rhodium complexes containing several C4 bridged diphosphines, namely BINAP, dppb, dppx and dcpb as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes. In the third chapter I report on an investigation into how electronic properties and coordination mode affect the elimination of phosphonium salts from rhodium complexes. The stability of a range of monodentate, bidentate and tridentate rhodium-phosphine complexes was tested. I also report on the formation of a novel bidentate complex containing a partially quaternised TRIPHOS ligand and investigate the mechanism of formation using 13CH3I. Strong evidence is also presented supporting a dissociative mechanism as the means of phosphine loss from the rhodium centre. In the final chapters I report an investigation into the stability of rhodium-aminophosphine ligand complexes and into increasing the solubility of potential rhodium pre-catalysts through the use of amine-containing phosphine ligands.
93

In-vivo 31 P Magnetresonanzspektroskopie bei repetitiver transarterieller Chemoembolisation maligner Lebertumoren

Schuster, Adrian 20 December 2002 (has links)
Mit der palliativen transarteriellen Chemoembolisation (TACE) läßt sich eine Verkleinerung von malignen Lebertumoren und eine Verlängerung des Überlebens erreichen. Im Verlauf des Therapiezyklus diente die Phosphor-Magnetresonanzspektroskopie mittels Chemical-Shift-Imaging einem nichtinvasiven Einblick in den zellulären Energie- und Membranstoffwechsel. Eine Differenzierung zwischen primären und sekundären Lebertumoren war anhand der 31P-Spektren nicht möglich. Posttherapeutisch zeigten die Patienten einen Anstieg des anorganischen Phosphats bei Abfall des ß-NTP-Signals, die sich während des sechswöchigen Intervalls vor der nächsten Intervention wieder normalisierten. Therapieansprechen und -versagen zeigten während des Therapiezyklus unterschiedliche spektroskopische Quotientenverläufe. Eine deutliche Volumenreduktion als auch eine homogene und dauerhafte Lipiodoleinlagerung im Tumor gehen zuverlässig mit einem spektroskopischen Therapieansprechen einher. Dies zeigte sich bei der ersten Patientengruppe während der Untersuchung direkt nach der Embolisation und bei der zweiten Gruppe erst vor der nächsten Intervention. Therapieversagen, Tumorprogression und geringe Lipiodoleinlagerung bzw. rasche Entspeicherung im Verlauf ließen sich spektroskopisch nach-weisen. Schwierig bleibt die Zuordnung der Patienten mit uneinheitlichen Quotienten-verläufen. Die MRS kann früher als die klinische Routinediagnostik eine Aussage über das Therapieansprechen treffen. Für den Patienten ergibt sich die Vermeidung einer ineffektiven Therapie. Bei nachgewiesenem Ansprechen hingegen profitiert der Patient durch die wiederholte Anwendung der TACE. Der hohe personelle, technische und zeitliche Aufwand für die Phosphorspektroskopie verhindert bisher den klinischen Routineeinsatz dieses Verfahrens. Im Rahmen der klinischen Forschung, insbe-sondere in der onkologischen Therapiekontrolle, hat die MRS als nichtinvasive Methode heute einen großen Stellenwert. / Using palliative transarterial chemoembolization (TACE) a reduction of malignant liver neoplasms and a prolongation of survival time can be achieved. During the course of therapy phosphorous magnetic resonance spectroscopy by means of chemical-shift-imaging was used for noninvasive examination of the cellular metabolism of energy and membranes. Differentiation between primary and secondary liver tumors was not feasible using 31P-spectra. After therapy patients had shown increased inorganic phosphate signal and reduction of the ß-NTP-signals, which normalized during six week intervall before next intervention. Response and non-response to therapy showed different courses of spectroscopic quotients during therapy cycle. Prominent reduction of volume as well as homogeneous and continous retention of lipiodol within the tumor are reliable combined with spectroscopic response to therapy. The first group of patients showed these signs at the examination immediately after embolization whereas patients of the second group showed these signs not before next intervention. Failure of therapy, progression of tumor and slight retention of lipiodol or rapid elemination during course of therapy were detectable by spectroscopy. Categorization of patients with non-uniform courses of quotients remains difficult. Magnetic resonance spectroscopy is able to determine response to therapy earlier than standard diagnostic methods. As a result ineffective therapy is avoided for the patient. On the other hand the patient profits from repeated administration of TACE. Great expense of personnel, equipment and time so far prevents clinical use of phosphorous spectroscopy as a matter of routine. In conjunction with clinical research MRS is an important non-invasive method especially for oncological therapy monitoring.
94

Modelo SWAT2005 aplicado às sub-bacias dos rios Conrado e Pinheiro Pato Branco-PR / Model SWAT2005 aplicability to conrado and pinheiro river watersheds - Pato Branco/PR

Baltokoski, Valmir 30 June 2008 (has links)
Made available in DSpace on 2017-07-10T19:24:31Z (GMT). No. of bitstreams: 1 Valmir Baltokoski.pdf: 2787750 bytes, checksum: fe61cb2f7c894d46e777852e6fec1e06 (MD5) Previous issue date: 2008-06-30 / Hydrological models developing that may to predict the nonpoint source pollution and the land use and occupation impacts on water quality has been a powerful tool at agricultural systems study. Within this context, the objective of the present research work was to evaluate the SWAT 2005 (Soil and Water Assessment Tool) applicability to simulate surface runoff, sediments yield and total phosphorous flow mass. The research was developed in two contiguous watersheds, from Conrado and Pinheiro rivers, on the Pato Branco River basin, from Pato Branco and Mariopolis counties, Parana State. Climatological data relative to period 1979/2006 and observed data of flow rate, sediments yeld and total phosphorous concentration relative to 2004/2005 years, taken at two monitoring locations, were used. The model requires input data in spatial format concerning to land use and soils data, associated to a digital elevation model (DEM). It was used the AvSWAT_X interface with ArcView 3.3® and its extension Spatial Analyst 2.0®, for input and manipulation data. Monthly and yearly averages of flow rate, sediments yeld and total phosphorous mass flow were compared to the observed values, being this proceeding used in the model calibration and evaluation. The Nash-Sutcliffe Coefficient (COE) and the Sum of Deviations of the Simulated Data (Dv) were used to evaluate the modeling efficiency. The results have proved to be satisfactory for the several modelings. / O desenvolvimento de modelos hidrológicos capazes de predizer o impacto das fontes difusas de poluição e do uso e ocupação do solo na qualidade das águas, superficiais e subterrâneas, tem sido de grande auxílio no estudo de agroecossistemas agrícolas. Com esse objetivo, foi utilizado o modelo Soil and Water Assessment Tool (SWAT 2005), para avaliar sua aplicabilidade na previsão de escoamento superficial, na produção de sedimentos e no fluxo de massa do fósforo total, utilizando técnicas de análise de sensibilidade e calibração. O estudo foi realizado em duas microbacias hidrográficas contíguas, dos rios Conrado e Pinheiro, afluentes do Rio Pato Branco, localizadas nos municípios de Pato Branco e Mariópolis, no Estado do Paraná. Foram utilizados dados climatológicos do período de 1979/2006 e dados observados de vazão, sedimentos e concentração de fósforo total dos anos 2004/2005 de duas estações de monitoramento instaladas na área de estudo. O modelo requer dados espacializados de usos e tipos de solos, associados com banco de dados e um Modelo Digital de Elevação. Utilizou-se a interface AvSWAT_X, com o ArcView 3.3® e a extensão Spatial Analyst 2.0®, para entrada e manipulação dos dados no modelo. As médias anuais e mensais das simulações de vazão, sedimentos e fósforo total, foram comparadas com os dados observados, procedimento que serviu para calibrar o modelo e avaliar seu desempenho. Tanto o coeficiente de eficiência de Nash-Sutcliffe (COE) como a soma dos desvios dos dados simulados em relação aos dados observados (Dv) foram utilizados para avaliar a eficiência do modelo. Os resultados mostraram-se satisfatórios para as várias modelagens realizadas.
95

Modelo SWAT2005 aplicado às sub-bacias dos rios Conrado e Pinheiro Pato Branco-PR / Model SWAT2005 aplicability to conrado and pinheiro river watersheds - Pato Branco/PR

Baltokoski, Valmir 30 June 2008 (has links)
Made available in DSpace on 2017-05-12T14:47:51Z (GMT). No. of bitstreams: 1 Valmir Baltokoski.pdf: 2787750 bytes, checksum: fe61cb2f7c894d46e777852e6fec1e06 (MD5) Previous issue date: 2008-06-30 / Hydrological models developing that may to predict the nonpoint source pollution and the land use and occupation impacts on water quality has been a powerful tool at agricultural systems study. Within this context, the objective of the present research work was to evaluate the SWAT 2005 (Soil and Water Assessment Tool) applicability to simulate surface runoff, sediments yield and total phosphorous flow mass. The research was developed in two contiguous watersheds, from Conrado and Pinheiro rivers, on the Pato Branco River basin, from Pato Branco and Mariopolis counties, Parana State. Climatological data relative to period 1979/2006 and observed data of flow rate, sediments yeld and total phosphorous concentration relative to 2004/2005 years, taken at two monitoring locations, were used. The model requires input data in spatial format concerning to land use and soils data, associated to a digital elevation model (DEM). It was used the AvSWAT_X interface with ArcView 3.3® and its extension Spatial Analyst 2.0®, for input and manipulation data. Monthly and yearly averages of flow rate, sediments yeld and total phosphorous mass flow were compared to the observed values, being this proceeding used in the model calibration and evaluation. The Nash-Sutcliffe Coefficient (COE) and the Sum of Deviations of the Simulated Data (Dv) were used to evaluate the modeling efficiency. The results have proved to be satisfactory for the several modelings. / O desenvolvimento de modelos hidrológicos capazes de predizer o impacto das fontes difusas de poluição e do uso e ocupação do solo na qualidade das águas, superficiais e subterrâneas, tem sido de grande auxílio no estudo de agroecossistemas agrícolas. Com esse objetivo, foi utilizado o modelo Soil and Water Assessment Tool (SWAT 2005), para avaliar sua aplicabilidade na previsão de escoamento superficial, na produção de sedimentos e no fluxo de massa do fósforo total, utilizando técnicas de análise de sensibilidade e calibração. O estudo foi realizado em duas microbacias hidrográficas contíguas, dos rios Conrado e Pinheiro, afluentes do Rio Pato Branco, localizadas nos municípios de Pato Branco e Mariópolis, no Estado do Paraná. Foram utilizados dados climatológicos do período de 1979/2006 e dados observados de vazão, sedimentos e concentração de fósforo total dos anos 2004/2005 de duas estações de monitoramento instaladas na área de estudo. O modelo requer dados espacializados de usos e tipos de solos, associados com banco de dados e um Modelo Digital de Elevação. Utilizou-se a interface AvSWAT_X, com o ArcView 3.3® e a extensão Spatial Analyst 2.0®, para entrada e manipulação dos dados no modelo. As médias anuais e mensais das simulações de vazão, sedimentos e fósforo total, foram comparadas com os dados observados, procedimento que serviu para calibrar o modelo e avaliar seu desempenho. Tanto o coeficiente de eficiência de Nash-Sutcliffe (COE) como a soma dos desvios dos dados simulados em relação aos dados observados (Dv) foram utilizados para avaliar a eficiência do modelo. Os resultados mostraram-se satisfatórios para as várias modelagens realizadas.
96

Sedimentprovtagning av dagvattendammar som ett alternativ till flödesproportionell vattenprovtagning / Sediment sampling in stormwater ponds as an alternative to flow-weighted water sampling

Persson, Annika January 2010 (has links)
<p>Stormwater run-off from surfaces such as roads or rooftops is often polluted with heavy metals and nutrients. Many of these substances can cause great damage in biota if they end up in the recipient. In Sweden constructed wetlands and ponds for treatment of stormwater are frequently used, since research has shown that these treatment ponds are reducing stormwater pollution considerably to a low cost. The knowledge of these pollutant removal mechanisms and how follow-up and assessment of the ponds should be performed is still limited.</p><p>To determine the pollutant removal efficiency of the stormwater ponds it is recommended that flow-weighted water samples are collected from both the inflow and the outflow of the pond. This method demands considerable resources of time and money for installations and analysis. Alternative methods for assessing pollutant removal are requested, methods with lower costs but relevant results. This thesis is investigating whether sediment sampling could be such an alternative.</p><p>Sediment core samples were taken in four stormwater ponds where flow-weighted water sampling has been performed as well. This makes it possible to compare the two methods. A method of sampling recently sedimented material was also tried out by constructing and placing sediment traps on the pond floor. Analysis of concentration of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and phosphorus were carried out.</p><p>The results show i.e. that the concentrations of heavy metals and phosphorus in the pond sediments decrease as the distance from the pond inlet increase. Comparing the two methods shows that the results from the sediment sampling are in the same order of magnitude as the results from the water sampling. Consequently, the conclusion states that a well executed sediment sampling may be an alternative to flow-weighted water sampling.</p> / NOS dagvatten
97

Sedimentprovtagning av dagvattendammar som ett alternativ till flödesproportionell vattenprovtagning / Sediment sampling in stormwater ponds as an alternative to flow-weighted water sampling

Persson, Annika January 2010 (has links)
Stormwater run-off from surfaces such as roads or rooftops is often polluted with heavy metals and nutrients. Many of these substances can cause great damage in biota if they end up in the recipient. In Sweden constructed wetlands and ponds for treatment of stormwater are frequently used, since research has shown that these treatment ponds are reducing stormwater pollution considerably to a low cost. The knowledge of these pollutant removal mechanisms and how follow-up and assessment of the ponds should be performed is still limited. To determine the pollutant removal efficiency of the stormwater ponds it is recommended that flow-weighted water samples are collected from both the inflow and the outflow of the pond. This method demands considerable resources of time and money for installations and analysis. Alternative methods for assessing pollutant removal are requested, methods with lower costs but relevant results. This thesis is investigating whether sediment sampling could be such an alternative. Sediment core samples were taken in four stormwater ponds where flow-weighted water sampling has been performed as well. This makes it possible to compare the two methods. A method of sampling recently sedimented material was also tried out by constructing and placing sediment traps on the pond floor. Analysis of concentration of six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and phosphorus were carried out. The results show i.e. that the concentrations of heavy metals and phosphorus in the pond sediments decrease as the distance from the pond inlet increase. Comparing the two methods shows that the results from the sediment sampling are in the same order of magnitude as the results from the water sampling. Consequently, the conclusion states that a well executed sediment sampling may be an alternative to flow-weighted water sampling. / NOS dagvatten
98

Kungsängsverkets kväverening : inverkan på den interna fosforbelastningen i Ekoln / Kungsängsverkets nitrogen removal : effect on the internal phosphosous load in Ekoln

Lousa-Alvin, Alexandra January 2011 (has links)
Många sjöar är idag påverkade av mänsklig aktivitet, bland annat är 1 % av Sveriges sjöar eutrofierade, däribland Ekoln. Ekoln är en stor sjö i Uppsala län söder om Uppsala som länge varit eutrofierad. Fyrisån och Örsundaån är de största inflödena till Ekoln och Sävjaån är ett betydande biflöde till Fyrisån. Kungsängsverket är Uppsalas reningsverk och har sitt utlopp i Fyrisån och som ett led i att minska eutrofieringen byggdes fosforreningen ut 1972. Fosforhalterna i Ekoln sjönk och algblomningarna blev färre. Kvävereningen byggdes ut 1999 och i detta arbete utvärderas detta reningssteg.   Hypotesen är att när ammonium minskar i bottenvattnet kommer syrgasförhållandena att förbättras på grund av minskad ammoniumnedbrytning som förbrukar syrgas. Med ökad halt syrgas är det känt sedan tidigare studier att den interna fosforbelastningen och algblomningen minskar.   För att undersöka om det skett en signifikant minskning av näringsämnen i intransporten till Ekoln och av halterna i Ekoln utfördes statistiska test av ämnena för perioden före och perioden efter införandet av kväverening. Intransporterna modellerades även i StormTac.   Resultatet visar att det skett en minskning av kväve- och ammoniumtransport och en ökning av fosfor-, fosfat- och TOC-transport. I Ekoln har en minskning påvisats i ammonium-, totalfosforhalt och en ökning i fosfat- och TOC-halt. Ammoniumhalten har minskat i bottenvattnet så den minskade intransporten av ammonium gett en effekt. Fosfor- och fosfathalten har inte förändrats signifikant i bottenvattnet, men det har skett en viss minskning av fosfor och en viss ökning av fosfat i Ekoln perioden 1990-1998 till 2000-2010. Även syrgashalten har ökat i bottenvattnet.   Att det inte skett signifikanta förändringar i fosfor, fosfat och syrgas tyder på att intransporten till vattenmassan inte förändrats. Ökade TOC-halter leder till ökad nedbrytning där syrgas förbrukas i bottenvattnet. Det är möjligt att situationen sett ännu värre ut i Ekoln om inte kväveutsläppen minskat.
99

Investigations Of Open-Framework Metal Phosphates, Phosphites And Phosphite-Oxalate Materials

Mandal, Sukhendu 08 1900 (has links)
Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids. Most of them are based upon oxygen containing materials especially phosphates, and they exhibit fascinating architectures with unusual bonding and coordination environment. Besides metal phosphates and phosphites, inorganic-organic hybrids constitute an important family of open-framework structures. In this thesis, results of investigations of a variety of open-framework metal phosphates, metal phosphites, as well as a new family of phosphite-oxalates are presented. More importantly, studies directed towards the synthesis and understanding of the magnetic properties of various transition metal phosphates, phosphites, phosphite-oxalates and the upconversion behavior of uranium phosphites are discussed at length. In Chapter 1 of the thesis an overview of inorganic open-framework materials is presented. In Chapter 2 and 3, the synthesis, structure of open-framework zinc (Part A of both Chapters) and synthesis, structure and magnetic properties of open-framework iron (Part B of both Chapters) are presented. Some of these compounds show unusual structure and interesting properties. For example, two-dimensional iron phosphate exhibits ferrimagnetism whereas three-dimensional iron phosphate with SBU-6 and SBU-2 is antiferromagnetic. The three-dimensional iron phosphite exhibits small polarization at low field. In Chapter 4, we present a new family of organically templated hybrid materials synthesized by partially substituting the phosphite by the oxalate ion in manganese, iron and cobalt phosphites. These exhibit a wide range of structures in which the oxalates play an unusual dual role. Some of these compounds show interesting magnetic properties. For example, manganese phosphite-oxalate shows magnetic polarizations on application of high field at low temperatures and iron phosphite-oxalate exhibit ferromagnetism at very low temperature. While a large number of organically templated transition and main-group element phosphites have been synthesized, research on lanthanide and actinide phosphites has been rare. Most of the reported open-framework phosphate and phosphite compounds of uranium possess uranium in +6 oxidation state. The possibility of building open architectures of uranium phosphites has been explored in Chapter 5. The results have been rewarding and both layered and three-dimensional structures have been prepared. Two of them contain uranium in +4 state and exhibit upconversion behavior.
100

Sintese e marcacao com P-32 de fosfatos de monoalquila e do fosfato de monofenila sob forma de sais de bis-ciclohexilamonio. Determinacao de espectros de absorcao em infra-vermelho e de ressonancia nuclear magnetica

ALMEIDA, MARIA A.T.M. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:23:11Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:29Z (GMT). No. of bitstreams: 1 00636.pdf: 4746331 bytes, checksum: 49aa6e0eb3bdd9da261862a04bcb4b58 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

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