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  <xs:element name="LesseeFinanceLeaseSupplementalCashFlowInformationRelatedToFinanceLeaseTableTextBlock" id="pdsb_LesseeFinanceLeaseSupplementalCashFlowInformationRelatedToFinanceLeaseTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
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  <xs:element name="FinanceLeaseLiabilityToBePaidYearOneAndThereafter" id="pdsb_FinanceLeaseLiabilityToBePaidYearOneAndThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" />
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  <xs:element name="April2026SecuritiesPurchaseAgreementMember" id="pdsb_April2026SecuritiesPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="ProceedsFromDebtAndIssuanceOfWarrants" id="pdsb_ProceedsFromDebtAndIssuanceOfWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" />
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  <xs:element name="EquityIncentivePlan2018Member" id="pdsb_EquityIncentivePlan2018Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="EquityIncentivePlan2014Member" id="pdsb_EquityIncentivePlan2014Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="InducementPlan2019Member" id="pdsb_InducementPlan2019Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
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  <xs:element name="NumberOfDirectorsParticipatingInSecuritiesPurchaseOffering" id="pdsb_NumberOfDirectorsParticipatingInSecuritiesPurchaseOffering" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
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  <xs:element name="CombinedPurchasePricePerShareAndWarrant" id="pdsb_CombinedPurchasePricePerShareAndWarrant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="instant" />
  <xs:element name="PlacementSharesAvailableForFutureSale" id="pdsb_PlacementSharesAvailableForFutureSale" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" />
  <xs:element name="NumberOfCorporationsPurchasingTaxBenefits" id="pdsb_NumberOfCorporationsPurchasingTaxBenefits" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
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  <xs:element name="June2026SalesAgreementMember" id="pdsb_June2026SalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="SalesAgreementAndNewSalesAgreementMember" id="pdsb_SalesAgreementAndNewSalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
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  <xs:element name="AmendedAndRestatedAtMarketIssuanceSalesAgreementMember" id="pdsb_AmendedAndRestatedAtMarketIssuanceSalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="February2025OfferingMember" id="pdsb_February2025OfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="November2025OfferingMember" id="pdsb_November2025OfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
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  <xs:element name="SeniorSecuredConvertibleDebenturesMember" id="pdsb_SeniorSecuredConvertibleDebenturesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
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  <xs:element name="StockIssuedDuringPeriodValueExerciseOfPreFundedWarrants" id="pdsb_StockIssuedDuringPeriodValueExerciseOfPreFundedWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" />
  <xs:element name="StockIssuedDuringPeriodSharesExerciseOfPreFundedWarrants" id="pdsb_StockIssuedDuringPeriodSharesExerciseOfPreFundedWarrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
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</xs:schema>
